WSL2-Linux-Kernel/arch/mips/mm/context.c

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// SPDX-License-Identifier: GPL-2.0
MIPS: MemoryMapID (MMID) Support Introduce support for using MemoryMapIDs (MMIDs) as an alternative to Address Space IDs (ASIDs). The major difference between the two is that MMIDs are global - ie. an MMID uniquely identifies an address space across all coherent CPUs. In contrast ASIDs are non-global per-CPU IDs, wherein each address space is allocated a separate ASID for each CPU upon which it is used. This global namespace allows a new GINVT instruction be used to globally invalidate TLB entries associated with a particular MMID across all coherent CPUs in the system, removing the need for IPIs to invalidate entries with separate ASIDs on each CPU. The allocation scheme used here is largely borrowed from arm64 (see arch/arm64/mm/context.c). In essence we maintain a bitmap to track available MMIDs, and MMIDs in active use at the time of a rollover to a new MMID version are preserved in the new version. The allocation scheme requires efficient 64 bit atomics in order to perform reasonably, so this support depends upon CONFIG_GENERIC_ATOMIC64=n (ie. currently it will only be included in MIPS64 kernels). The first, and currently only, available CPU with support for MMIDs is the MIPS I6500. This CPU supports 16 bit MMIDs, and so for now we cap our MMIDs to 16 bits wide in order to prevent the bitmap growing to absurd sizes if any future CPU does implement 32 bit MMIDs as the architecture manuals suggest is recommended. When MMIDs are in use we also make use of GINVT instruction which is available due to the global nature of MMIDs. By executing a sequence of GINVT & SYNC 0x14 instructions we can avoid the overhead of an IPI to each remote CPU in many cases. One complication is that GINVT will invalidate wired entries (in all cases apart from type 0, which targets the entire TLB). In order to avoid GINVT invalidating any wired TLB entries we set up, we make sure to create those entries using a reserved MMID (0) that we never associate with any address space. Also of note is that KVM will require further work in order to support MMIDs & GINVT, since KVM is involved in allocating IDs for guests & in configuring the MMU. That work is not part of this patch, so for now when MMIDs are in use KVM is disabled. Signed-off-by: Paul Burton <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-02 04:43:28 +03:00
#include <linux/atomic.h>
#include <linux/mmu_context.h>
MIPS: MemoryMapID (MMID) Support Introduce support for using MemoryMapIDs (MMIDs) as an alternative to Address Space IDs (ASIDs). The major difference between the two is that MMIDs are global - ie. an MMID uniquely identifies an address space across all coherent CPUs. In contrast ASIDs are non-global per-CPU IDs, wherein each address space is allocated a separate ASID for each CPU upon which it is used. This global namespace allows a new GINVT instruction be used to globally invalidate TLB entries associated with a particular MMID across all coherent CPUs in the system, removing the need for IPIs to invalidate entries with separate ASIDs on each CPU. The allocation scheme used here is largely borrowed from arm64 (see arch/arm64/mm/context.c). In essence we maintain a bitmap to track available MMIDs, and MMIDs in active use at the time of a rollover to a new MMID version are preserved in the new version. The allocation scheme requires efficient 64 bit atomics in order to perform reasonably, so this support depends upon CONFIG_GENERIC_ATOMIC64=n (ie. currently it will only be included in MIPS64 kernels). The first, and currently only, available CPU with support for MMIDs is the MIPS I6500. This CPU supports 16 bit MMIDs, and so for now we cap our MMIDs to 16 bits wide in order to prevent the bitmap growing to absurd sizes if any future CPU does implement 32 bit MMIDs as the architecture manuals suggest is recommended. When MMIDs are in use we also make use of GINVT instruction which is available due to the global nature of MMIDs. By executing a sequence of GINVT & SYNC 0x14 instructions we can avoid the overhead of an IPI to each remote CPU in many cases. One complication is that GINVT will invalidate wired entries (in all cases apart from type 0, which targets the entire TLB). In order to avoid GINVT invalidating any wired TLB entries we set up, we make sure to create those entries using a reserved MMID (0) that we never associate with any address space. Also of note is that KVM will require further work in order to support MMIDs & GINVT, since KVM is involved in allocating IDs for guests & in configuring the MMU. That work is not part of this patch, so for now when MMIDs are in use KVM is disabled. Signed-off-by: Paul Burton <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-02 04:43:28 +03:00
#include <linux/percpu.h>
#include <linux/spinlock.h>
static DEFINE_RAW_SPINLOCK(cpu_mmid_lock);
static atomic64_t mmid_version;
static unsigned int num_mmids;
static unsigned long *mmid_map;
static DEFINE_PER_CPU(u64, reserved_mmids);
static cpumask_t tlb_flush_pending;
static bool asid_versions_eq(int cpu, u64 a, u64 b)
{
return ((a ^ b) & asid_version_mask(cpu)) == 0;
}
void get_new_mmu_context(struct mm_struct *mm)
{
unsigned int cpu;
u64 asid;
MIPS: MemoryMapID (MMID) Support Introduce support for using MemoryMapIDs (MMIDs) as an alternative to Address Space IDs (ASIDs). The major difference between the two is that MMIDs are global - ie. an MMID uniquely identifies an address space across all coherent CPUs. In contrast ASIDs are non-global per-CPU IDs, wherein each address space is allocated a separate ASID for each CPU upon which it is used. This global namespace allows a new GINVT instruction be used to globally invalidate TLB entries associated with a particular MMID across all coherent CPUs in the system, removing the need for IPIs to invalidate entries with separate ASIDs on each CPU. The allocation scheme used here is largely borrowed from arm64 (see arch/arm64/mm/context.c). In essence we maintain a bitmap to track available MMIDs, and MMIDs in active use at the time of a rollover to a new MMID version are preserved in the new version. The allocation scheme requires efficient 64 bit atomics in order to perform reasonably, so this support depends upon CONFIG_GENERIC_ATOMIC64=n (ie. currently it will only be included in MIPS64 kernels). The first, and currently only, available CPU with support for MMIDs is the MIPS I6500. This CPU supports 16 bit MMIDs, and so for now we cap our MMIDs to 16 bits wide in order to prevent the bitmap growing to absurd sizes if any future CPU does implement 32 bit MMIDs as the architecture manuals suggest is recommended. When MMIDs are in use we also make use of GINVT instruction which is available due to the global nature of MMIDs. By executing a sequence of GINVT & SYNC 0x14 instructions we can avoid the overhead of an IPI to each remote CPU in many cases. One complication is that GINVT will invalidate wired entries (in all cases apart from type 0, which targets the entire TLB). In order to avoid GINVT invalidating any wired TLB entries we set up, we make sure to create those entries using a reserved MMID (0) that we never associate with any address space. Also of note is that KVM will require further work in order to support MMIDs & GINVT, since KVM is involved in allocating IDs for guests & in configuring the MMU. That work is not part of this patch, so for now when MMIDs are in use KVM is disabled. Signed-off-by: Paul Burton <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-02 04:43:28 +03:00
/*
* This function is specific to ASIDs, and should not be called when
* MMIDs are in use.
*/
if (WARN_ON(IS_ENABLED(CONFIG_DEBUG_VM) && cpu_has_mmid))
return;
cpu = smp_processor_id();
asid = asid_cache(cpu);
if (!((asid += cpu_asid_inc()) & cpu_asid_mask(&cpu_data[cpu]))) {
if (cpu_has_vtag_icache)
flush_icache_all();
local_flush_tlb_all(); /* start new asid cycle */
}
set_cpu_context(cpu, mm, asid);
asid_cache(cpu) = asid;
}
EXPORT_SYMBOL_GPL(get_new_mmu_context);
void check_mmu_context(struct mm_struct *mm)
{
unsigned int cpu = smp_processor_id();
MIPS: MemoryMapID (MMID) Support Introduce support for using MemoryMapIDs (MMIDs) as an alternative to Address Space IDs (ASIDs). The major difference between the two is that MMIDs are global - ie. an MMID uniquely identifies an address space across all coherent CPUs. In contrast ASIDs are non-global per-CPU IDs, wherein each address space is allocated a separate ASID for each CPU upon which it is used. This global namespace allows a new GINVT instruction be used to globally invalidate TLB entries associated with a particular MMID across all coherent CPUs in the system, removing the need for IPIs to invalidate entries with separate ASIDs on each CPU. The allocation scheme used here is largely borrowed from arm64 (see arch/arm64/mm/context.c). In essence we maintain a bitmap to track available MMIDs, and MMIDs in active use at the time of a rollover to a new MMID version are preserved in the new version. The allocation scheme requires efficient 64 bit atomics in order to perform reasonably, so this support depends upon CONFIG_GENERIC_ATOMIC64=n (ie. currently it will only be included in MIPS64 kernels). The first, and currently only, available CPU with support for MMIDs is the MIPS I6500. This CPU supports 16 bit MMIDs, and so for now we cap our MMIDs to 16 bits wide in order to prevent the bitmap growing to absurd sizes if any future CPU does implement 32 bit MMIDs as the architecture manuals suggest is recommended. When MMIDs are in use we also make use of GINVT instruction which is available due to the global nature of MMIDs. By executing a sequence of GINVT & SYNC 0x14 instructions we can avoid the overhead of an IPI to each remote CPU in many cases. One complication is that GINVT will invalidate wired entries (in all cases apart from type 0, which targets the entire TLB). In order to avoid GINVT invalidating any wired TLB entries we set up, we make sure to create those entries using a reserved MMID (0) that we never associate with any address space. Also of note is that KVM will require further work in order to support MMIDs & GINVT, since KVM is involved in allocating IDs for guests & in configuring the MMU. That work is not part of this patch, so for now when MMIDs are in use KVM is disabled. Signed-off-by: Paul Burton <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-02 04:43:28 +03:00
/*
* This function is specific to ASIDs, and should not be called when
* MMIDs are in use.
*/
if (WARN_ON(IS_ENABLED(CONFIG_DEBUG_VM) && cpu_has_mmid))
return;
/* Check if our ASID is of an older version and thus invalid */
MIPS: MemoryMapID (MMID) Support Introduce support for using MemoryMapIDs (MMIDs) as an alternative to Address Space IDs (ASIDs). The major difference between the two is that MMIDs are global - ie. an MMID uniquely identifies an address space across all coherent CPUs. In contrast ASIDs are non-global per-CPU IDs, wherein each address space is allocated a separate ASID for each CPU upon which it is used. This global namespace allows a new GINVT instruction be used to globally invalidate TLB entries associated with a particular MMID across all coherent CPUs in the system, removing the need for IPIs to invalidate entries with separate ASIDs on each CPU. The allocation scheme used here is largely borrowed from arm64 (see arch/arm64/mm/context.c). In essence we maintain a bitmap to track available MMIDs, and MMIDs in active use at the time of a rollover to a new MMID version are preserved in the new version. The allocation scheme requires efficient 64 bit atomics in order to perform reasonably, so this support depends upon CONFIG_GENERIC_ATOMIC64=n (ie. currently it will only be included in MIPS64 kernels). The first, and currently only, available CPU with support for MMIDs is the MIPS I6500. This CPU supports 16 bit MMIDs, and so for now we cap our MMIDs to 16 bits wide in order to prevent the bitmap growing to absurd sizes if any future CPU does implement 32 bit MMIDs as the architecture manuals suggest is recommended. When MMIDs are in use we also make use of GINVT instruction which is available due to the global nature of MMIDs. By executing a sequence of GINVT & SYNC 0x14 instructions we can avoid the overhead of an IPI to each remote CPU in many cases. One complication is that GINVT will invalidate wired entries (in all cases apart from type 0, which targets the entire TLB). In order to avoid GINVT invalidating any wired TLB entries we set up, we make sure to create those entries using a reserved MMID (0) that we never associate with any address space. Also of note is that KVM will require further work in order to support MMIDs & GINVT, since KVM is involved in allocating IDs for guests & in configuring the MMU. That work is not part of this patch, so for now when MMIDs are in use KVM is disabled. Signed-off-by: Paul Burton <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-02 04:43:28 +03:00
if (!asid_versions_eq(cpu, cpu_context(cpu, mm), asid_cache(cpu)))
get_new_mmu_context(mm);
}
EXPORT_SYMBOL_GPL(check_mmu_context);
MIPS: MemoryMapID (MMID) Support Introduce support for using MemoryMapIDs (MMIDs) as an alternative to Address Space IDs (ASIDs). The major difference between the two is that MMIDs are global - ie. an MMID uniquely identifies an address space across all coherent CPUs. In contrast ASIDs are non-global per-CPU IDs, wherein each address space is allocated a separate ASID for each CPU upon which it is used. This global namespace allows a new GINVT instruction be used to globally invalidate TLB entries associated with a particular MMID across all coherent CPUs in the system, removing the need for IPIs to invalidate entries with separate ASIDs on each CPU. The allocation scheme used here is largely borrowed from arm64 (see arch/arm64/mm/context.c). In essence we maintain a bitmap to track available MMIDs, and MMIDs in active use at the time of a rollover to a new MMID version are preserved in the new version. The allocation scheme requires efficient 64 bit atomics in order to perform reasonably, so this support depends upon CONFIG_GENERIC_ATOMIC64=n (ie. currently it will only be included in MIPS64 kernels). The first, and currently only, available CPU with support for MMIDs is the MIPS I6500. This CPU supports 16 bit MMIDs, and so for now we cap our MMIDs to 16 bits wide in order to prevent the bitmap growing to absurd sizes if any future CPU does implement 32 bit MMIDs as the architecture manuals suggest is recommended. When MMIDs are in use we also make use of GINVT instruction which is available due to the global nature of MMIDs. By executing a sequence of GINVT & SYNC 0x14 instructions we can avoid the overhead of an IPI to each remote CPU in many cases. One complication is that GINVT will invalidate wired entries (in all cases apart from type 0, which targets the entire TLB). In order to avoid GINVT invalidating any wired TLB entries we set up, we make sure to create those entries using a reserved MMID (0) that we never associate with any address space. Also of note is that KVM will require further work in order to support MMIDs & GINVT, since KVM is involved in allocating IDs for guests & in configuring the MMU. That work is not part of this patch, so for now when MMIDs are in use KVM is disabled. Signed-off-by: Paul Burton <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-02 04:43:28 +03:00
static void flush_context(void)
{
u64 mmid;
int cpu;
/* Update the list of reserved MMIDs and the MMID bitmap */
bitmap_clear(mmid_map, 0, num_mmids);
/* Reserve an MMID for kmap/wired entries */
__set_bit(MMID_KERNEL_WIRED, mmid_map);
for_each_possible_cpu(cpu) {
mmid = xchg_relaxed(&cpu_data[cpu].asid_cache, 0);
/*
* If this CPU has already been through a
* rollover, but hasn't run another task in
* the meantime, we must preserve its reserved
* MMID, as this is the only trace we have of
* the process it is still running.
*/
if (mmid == 0)
mmid = per_cpu(reserved_mmids, cpu);
__set_bit(mmid & cpu_asid_mask(&cpu_data[cpu]), mmid_map);
per_cpu(reserved_mmids, cpu) = mmid;
}
/*
* Queue a TLB invalidation for each CPU to perform on next
* context-switch
*/
cpumask_setall(&tlb_flush_pending);
}
static bool check_update_reserved_mmid(u64 mmid, u64 newmmid)
{
bool hit;
int cpu;
/*
* Iterate over the set of reserved MMIDs looking for a match.
* If we find one, then we can update our mm to use newmmid
* (i.e. the same MMID in the current generation) but we can't
* exit the loop early, since we need to ensure that all copies
* of the old MMID are updated to reflect the mm. Failure to do
* so could result in us missing the reserved MMID in a future
* generation.
*/
hit = false;
for_each_possible_cpu(cpu) {
if (per_cpu(reserved_mmids, cpu) == mmid) {
hit = true;
per_cpu(reserved_mmids, cpu) = newmmid;
}
}
return hit;
}
static u64 get_new_mmid(struct mm_struct *mm)
{
static u32 cur_idx = MMID_KERNEL_WIRED + 1;
u64 mmid, version, mmid_mask;
mmid = cpu_context(0, mm);
version = atomic64_read(&mmid_version);
mmid_mask = cpu_asid_mask(&boot_cpu_data);
if (!asid_versions_eq(0, mmid, 0)) {
u64 newmmid = version | (mmid & mmid_mask);
/*
* If our current MMID was active during a rollover, we
* can continue to use it and this was just a false alarm.
*/
if (check_update_reserved_mmid(mmid, newmmid)) {
mmid = newmmid;
goto set_context;
}
/*
* We had a valid MMID in a previous life, so try to re-use
* it if possible.
*/
if (!__test_and_set_bit(mmid & mmid_mask, mmid_map)) {
mmid = newmmid;
goto set_context;
}
}
/* Allocate a free MMID */
mmid = find_next_zero_bit(mmid_map, num_mmids, cur_idx);
if (mmid != num_mmids)
goto reserve_mmid;
/* We're out of MMIDs, so increment the global version */
version = atomic64_add_return_relaxed(asid_first_version(0),
&mmid_version);
/* Note currently active MMIDs & mark TLBs as requiring flushes */
flush_context();
/* We have more MMIDs than CPUs, so this will always succeed */
mmid = find_first_zero_bit(mmid_map, num_mmids);
reserve_mmid:
__set_bit(mmid, mmid_map);
cur_idx = mmid;
mmid |= version;
set_context:
set_cpu_context(0, mm, mmid);
return mmid;
}
void check_switch_mmu_context(struct mm_struct *mm)
{
unsigned int cpu = smp_processor_id();
MIPS: MemoryMapID (MMID) Support Introduce support for using MemoryMapIDs (MMIDs) as an alternative to Address Space IDs (ASIDs). The major difference between the two is that MMIDs are global - ie. an MMID uniquely identifies an address space across all coherent CPUs. In contrast ASIDs are non-global per-CPU IDs, wherein each address space is allocated a separate ASID for each CPU upon which it is used. This global namespace allows a new GINVT instruction be used to globally invalidate TLB entries associated with a particular MMID across all coherent CPUs in the system, removing the need for IPIs to invalidate entries with separate ASIDs on each CPU. The allocation scheme used here is largely borrowed from arm64 (see arch/arm64/mm/context.c). In essence we maintain a bitmap to track available MMIDs, and MMIDs in active use at the time of a rollover to a new MMID version are preserved in the new version. The allocation scheme requires efficient 64 bit atomics in order to perform reasonably, so this support depends upon CONFIG_GENERIC_ATOMIC64=n (ie. currently it will only be included in MIPS64 kernels). The first, and currently only, available CPU with support for MMIDs is the MIPS I6500. This CPU supports 16 bit MMIDs, and so for now we cap our MMIDs to 16 bits wide in order to prevent the bitmap growing to absurd sizes if any future CPU does implement 32 bit MMIDs as the architecture manuals suggest is recommended. When MMIDs are in use we also make use of GINVT instruction which is available due to the global nature of MMIDs. By executing a sequence of GINVT & SYNC 0x14 instructions we can avoid the overhead of an IPI to each remote CPU in many cases. One complication is that GINVT will invalidate wired entries (in all cases apart from type 0, which targets the entire TLB). In order to avoid GINVT invalidating any wired TLB entries we set up, we make sure to create those entries using a reserved MMID (0) that we never associate with any address space. Also of note is that KVM will require further work in order to support MMIDs & GINVT, since KVM is involved in allocating IDs for guests & in configuring the MMU. That work is not part of this patch, so for now when MMIDs are in use KVM is disabled. Signed-off-by: Paul Burton <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-02 04:43:28 +03:00
u64 ctx, old_active_mmid;
unsigned long flags;
MIPS: MemoryMapID (MMID) Support Introduce support for using MemoryMapIDs (MMIDs) as an alternative to Address Space IDs (ASIDs). The major difference between the two is that MMIDs are global - ie. an MMID uniquely identifies an address space across all coherent CPUs. In contrast ASIDs are non-global per-CPU IDs, wherein each address space is allocated a separate ASID for each CPU upon which it is used. This global namespace allows a new GINVT instruction be used to globally invalidate TLB entries associated with a particular MMID across all coherent CPUs in the system, removing the need for IPIs to invalidate entries with separate ASIDs on each CPU. The allocation scheme used here is largely borrowed from arm64 (see arch/arm64/mm/context.c). In essence we maintain a bitmap to track available MMIDs, and MMIDs in active use at the time of a rollover to a new MMID version are preserved in the new version. The allocation scheme requires efficient 64 bit atomics in order to perform reasonably, so this support depends upon CONFIG_GENERIC_ATOMIC64=n (ie. currently it will only be included in MIPS64 kernels). The first, and currently only, available CPU with support for MMIDs is the MIPS I6500. This CPU supports 16 bit MMIDs, and so for now we cap our MMIDs to 16 bits wide in order to prevent the bitmap growing to absurd sizes if any future CPU does implement 32 bit MMIDs as the architecture manuals suggest is recommended. When MMIDs are in use we also make use of GINVT instruction which is available due to the global nature of MMIDs. By executing a sequence of GINVT & SYNC 0x14 instructions we can avoid the overhead of an IPI to each remote CPU in many cases. One complication is that GINVT will invalidate wired entries (in all cases apart from type 0, which targets the entire TLB). In order to avoid GINVT invalidating any wired TLB entries we set up, we make sure to create those entries using a reserved MMID (0) that we never associate with any address space. Also of note is that KVM will require further work in order to support MMIDs & GINVT, since KVM is involved in allocating IDs for guests & in configuring the MMU. That work is not part of this patch, so for now when MMIDs are in use KVM is disabled. Signed-off-by: Paul Burton <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-02 04:43:28 +03:00
if (!cpu_has_mmid) {
check_mmu_context(mm);
write_c0_entryhi(cpu_asid(cpu, mm));
goto setup_pgd;
}
/*
* MMID switch fast-path, to avoid acquiring cpu_mmid_lock when it's
* unnecessary.
*
* The memory ordering here is subtle. If our active_mmids is non-zero
* and the MMID matches the current version, then we update the CPU's
* asid_cache with a relaxed cmpxchg. Racing with a concurrent rollover
* means that either:
*
* - We get a zero back from the cmpxchg and end up waiting on
* cpu_mmid_lock in check_mmu_context(). Taking the lock synchronises
* with the rollover and so we are forced to see the updated
* generation.
*
* - We get a valid MMID back from the cmpxchg, which means the
* relaxed xchg in flush_context will treat us as reserved
* because atomic RmWs are totally ordered for a given location.
*/
ctx = cpu_context(cpu, mm);
old_active_mmid = READ_ONCE(cpu_data[cpu].asid_cache);
if (!old_active_mmid ||
!asid_versions_eq(cpu, ctx, atomic64_read(&mmid_version)) ||
!cmpxchg_relaxed(&cpu_data[cpu].asid_cache, old_active_mmid, ctx)) {
raw_spin_lock_irqsave(&cpu_mmid_lock, flags);
ctx = cpu_context(cpu, mm);
if (!asid_versions_eq(cpu, ctx, atomic64_read(&mmid_version)))
ctx = get_new_mmid(mm);
WRITE_ONCE(cpu_data[cpu].asid_cache, ctx);
raw_spin_unlock_irqrestore(&cpu_mmid_lock, flags);
}
/*
* Invalidate the local TLB if needed. Note that we must only clear our
* bit in tlb_flush_pending after this is complete, so that the
* cpu_has_shared_ftlb_entries case below isn't misled.
*/
if (cpumask_test_cpu(cpu, &tlb_flush_pending)) {
if (cpu_has_vtag_icache)
flush_icache_all();
local_flush_tlb_all();
cpumask_clear_cpu(cpu, &tlb_flush_pending);
}
write_c0_memorymapid(ctx & cpu_asid_mask(&boot_cpu_data));
/*
* If this CPU shares FTLB entries with its siblings and one or more of
* those siblings hasn't yet invalidated its TLB following a version
* increase then we need to invalidate any TLB entries for our MMID
* that we might otherwise pick up from a sibling.
*
* We ifdef on CONFIG_SMP because cpu_sibling_map isn't defined in
* CONFIG_SMP=n kernels.
*/
#ifdef CONFIG_SMP
if (cpu_has_shared_ftlb_entries &&
cpumask_intersects(&tlb_flush_pending, &cpu_sibling_map[cpu])) {
/* Ensure we operate on the new MMID */
mtc0_tlbw_hazard();
/*
* Invalidate all TLB entries associated with the new
* MMID, and wait for the invalidation to complete.
*/
ginvt_mmid();
sync_ginv();
}
#endif
setup_pgd:
TLBMISS_HANDLER_SETUP_PGD(mm->pgd);
}
EXPORT_SYMBOL_GPL(check_switch_mmu_context);
MIPS: MemoryMapID (MMID) Support Introduce support for using MemoryMapIDs (MMIDs) as an alternative to Address Space IDs (ASIDs). The major difference between the two is that MMIDs are global - ie. an MMID uniquely identifies an address space across all coherent CPUs. In contrast ASIDs are non-global per-CPU IDs, wherein each address space is allocated a separate ASID for each CPU upon which it is used. This global namespace allows a new GINVT instruction be used to globally invalidate TLB entries associated with a particular MMID across all coherent CPUs in the system, removing the need for IPIs to invalidate entries with separate ASIDs on each CPU. The allocation scheme used here is largely borrowed from arm64 (see arch/arm64/mm/context.c). In essence we maintain a bitmap to track available MMIDs, and MMIDs in active use at the time of a rollover to a new MMID version are preserved in the new version. The allocation scheme requires efficient 64 bit atomics in order to perform reasonably, so this support depends upon CONFIG_GENERIC_ATOMIC64=n (ie. currently it will only be included in MIPS64 kernels). The first, and currently only, available CPU with support for MMIDs is the MIPS I6500. This CPU supports 16 bit MMIDs, and so for now we cap our MMIDs to 16 bits wide in order to prevent the bitmap growing to absurd sizes if any future CPU does implement 32 bit MMIDs as the architecture manuals suggest is recommended. When MMIDs are in use we also make use of GINVT instruction which is available due to the global nature of MMIDs. By executing a sequence of GINVT & SYNC 0x14 instructions we can avoid the overhead of an IPI to each remote CPU in many cases. One complication is that GINVT will invalidate wired entries (in all cases apart from type 0, which targets the entire TLB). In order to avoid GINVT invalidating any wired TLB entries we set up, we make sure to create those entries using a reserved MMID (0) that we never associate with any address space. Also of note is that KVM will require further work in order to support MMIDs & GINVT, since KVM is involved in allocating IDs for guests & in configuring the MMU. That work is not part of this patch, so for now when MMIDs are in use KVM is disabled. Signed-off-by: Paul Burton <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org
2019-02-02 04:43:28 +03:00
static int mmid_init(void)
{
if (!cpu_has_mmid)
return 0;
/*
* Expect allocation after rollover to fail if we don't have at least
* one more MMID than CPUs.
*/
num_mmids = asid_first_version(0);
WARN_ON(num_mmids <= num_possible_cpus());
atomic64_set(&mmid_version, asid_first_version(0));
mmid_map = kcalloc(BITS_TO_LONGS(num_mmids), sizeof(*mmid_map),
GFP_KERNEL);
if (!mmid_map)
panic("Failed to allocate bitmap for %u MMIDs\n", num_mmids);
/* Reserve an MMID for kmap/wired entries */
__set_bit(MMID_KERNEL_WIRED, mmid_map);
pr_info("MMID allocator initialised with %u entries\n", num_mmids);
return 0;
}
early_initcall(mmid_init);