Merge branch 'stable/for-linus-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb

Pull swiotlb update from Konrad Rzeszutek Wilk:
 "A generic (but for right now engaged only with AMD SEV) mechanism to
  adjust a larger size SWIOTLB based on the total memory of the SEV
  guests which right now require the bounce buffer for interacting with
  the outside world.

  Normal knobs (swiotlb=XYZ) still work"

* 'stable/for-linus-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb:
  x86,swiotlb: Adjust SWIOTLB bounce buffer size for SEV guests

arch/x86/include/asm/mem_encrypt.h

@@ -37,6 +37,7 @@ void __init sme_map_bootdata(char *real_mode_data);
 void __init sme_unmap_bootdata(char *real_mode_data);
 
 void __init sme_early_init(void);
+void __init sev_setup_arch(void);
 
 void __init sme_encrypt_kernel(struct boot_params *bp);
 void __init sme_enable(struct boot_params *bp);
@@ -69,6 +70,7 @@ static inline void __init sme_map_bootdata(char *real_mode_data) { }
 static inline void __init sme_unmap_bootdata(char *real_mode_data) { }
 
 static inline void __init sme_early_init(void) { }
+static inline void __init sev_setup_arch(void) { }
 
 static inline void __init sme_encrypt_kernel(struct boot_params *bp) { }
 static inline void __init sme_enable(struct boot_params *bp) { }

arch/x86/kernel/setup.c

@@ -1049,6 +1049,12 @@ void __init setup_arch(char **cmdline_p)
 	memblock_set_current_limit(ISA_END_ADDRESS);
 	e820__memblock_setup();
 
+	/*
+	 * Needs to run after memblock setup because it needs the physical
+	 * memory size.
+	 */
+	sev_setup_arch();
+
 	reserve_bios_regions();
 
 	efi_fake_memmap();

arch/x86/mm/mem_encrypt.c

@@ -198,6 +198,37 @@ void __init sme_early_init(void)
 		swiotlb_force = SWIOTLB_FORCE;
 }
 
+void __init sev_setup_arch(void)
+{
+	phys_addr_t total_mem = memblock_phys_mem_size();
+	unsigned long size;
+
+	if (!sev_active())
+		return;
+
+	/*
+	 * For SEV, all DMA has to occur via shared/unencrypted pages.
+	 * SEV uses SWIOTLB to make this happen without changing device
+	 * drivers. However, depending on the workload being run, the
+	 * default 64MB of SWIOTLB may not be enough and SWIOTLB may
+	 * run out of buffers for DMA, resulting in I/O errors and/or
+	 * performance degradation especially with high I/O workloads.
+	 *
+	 * Adjust the default size of SWIOTLB for SEV guests using
+	 * a percentage of guest memory for SWIOTLB buffers.
+	 * Also, as the SWIOTLB bounce buffer memory is allocated
+	 * from low memory, ensure that the adjusted size is within
+	 * the limits of low available memory.
+	 *
+	 * The percentage of guest memory used here for SWIOTLB buffers
+	 * is more of an approximation of the static adjustment which
+	 * 64MB for <1G, and ~128M to 256M for 1G-to-4G, i.e., the 6%
+	 */
+	size = total_mem * 6 / 100;
+	size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
+	swiotlb_adjust_size(size);
+}
+
 static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 {
 	pgprot_t old_prot, new_prot;

include/linux/swiotlb.h

@@ -30,6 +30,9 @@ enum swiotlb_force {
  */
 #define IO_TLB_SHIFT 11
 
+/* default to 64MB */
+#define IO_TLB_DEFAULT_SIZE (64UL<<20)
+
 extern void swiotlb_init(int verbose);
 int swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose);
 extern unsigned long swiotlb_nr_tbl(void);
@@ -78,6 +81,7 @@ void __init swiotlb_exit(void);
 unsigned int swiotlb_max_segment(void);
 size_t swiotlb_max_mapping_size(struct device *dev);
 bool is_swiotlb_active(void);
+void __init swiotlb_adjust_size(unsigned long new_size);
 #else
 #define swiotlb_force SWIOTLB_NO_FORCE
 static inline bool is_swiotlb_buffer(phys_addr_t paddr)
@@ -100,6 +104,10 @@ static inline bool is_swiotlb_active(void)
 {
 	return false;
 }
+
+static inline void swiotlb_adjust_size(unsigned long new_size)
+{
+}
 #endif /* CONFIG_SWIOTLB */
 
 extern void swiotlb_print_info(void);

kernel/dma/swiotlb.c

@@ -152,8 +152,6 @@ void swiotlb_set_max_segment(unsigned int val)
 		max_segment = rounddown(val, PAGE_SIZE);
 }
 
-/* default to 64MB */
-#define IO_TLB_DEFAULT_SIZE (64UL<<20)
 unsigned long swiotlb_size_or_default(void)
 {
 	unsigned long size;
@@ -163,6 +161,24 @@ unsigned long swiotlb_size_or_default(void)
 	return size ? size : (IO_TLB_DEFAULT_SIZE);
 }
 
+void __init swiotlb_adjust_size(unsigned long new_size)
+{
+	unsigned long size;
+
+	/*
+	 * If swiotlb parameter has not been specified, give a chance to
+	 * architectures such as those supporting memory encryption to
+	 * adjust/expand SWIOTLB size for their use.
+	 */
+	if (!io_tlb_nslabs) {
+		size = ALIGN(new_size, 1 << IO_TLB_SHIFT);
+		io_tlb_nslabs = size >> IO_TLB_SHIFT;
+		io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
+
+		pr_info("SWIOTLB bounce buffer size adjusted to %luMB", size >> 20);
+	}
+}
+
 void swiotlb_print_info(void)
 {
 	unsigned long bytes = io_tlb_nslabs << IO_TLB_SHIFT;