From 5236756d04454c7ce9f45e27b434d75b8d6f8759 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Tue, 23 Nov 2021 19:52:16 +1000 Subject: [PATCH] KVM: PPC: Book3S HV P9: Use Linux SPR save/restore to manage some host SPRs Linux implements SPR save/restore including storage space for registers in the task struct for process context switching. Make use of this similarly to the way we make use of the context switching fp/vec save restore. This improves code reuse, allows some stack space to be saved, and helps with avoiding VRSAVE updates if they are not required. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211123095231.1036501-39-npiggin@gmail.com --- arch/powerpc/include/asm/switch_to.h | 1 + arch/powerpc/kernel/process.c | 6 ++ arch/powerpc/kvm/book3s_hv.c | 21 +----- arch/powerpc/kvm/book3s_hv.h | 3 - arch/powerpc/kvm/book3s_hv_p9_entry.c | 93 +++++++++++++++++++-------- 5 files changed, 73 insertions(+), 51 deletions(-) diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h index e8013cd6b646..1f43ef696033 100644 --- a/arch/powerpc/include/asm/switch_to.h +++ b/arch/powerpc/include/asm/switch_to.h @@ -113,6 +113,7 @@ static inline void clear_task_ebb(struct task_struct *t) } void kvmppc_save_user_regs(void); +void kvmppc_save_current_sprs(void); extern int set_thread_tidr(struct task_struct *t); diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 8f841fbe16ad..5d2333d2a283 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1182,6 +1182,12 @@ void kvmppc_save_user_regs(void) #endif } EXPORT_SYMBOL_GPL(kvmppc_save_user_regs); + +void kvmppc_save_current_sprs(void) +{ + save_sprs(¤t->thread); +} +EXPORT_SYMBOL_GPL(kvmppc_save_current_sprs); #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */ static inline void restore_sprs(struct thread_struct *old_thread, diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 198f6d997330..7d48aa8aebb2 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -4566,9 +4566,6 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu) struct kvm_run *run = vcpu->run; int r; int srcu_idx; - unsigned long ebb_regs[3] = {}; /* shut up GCC */ - unsigned long user_tar = 0; - unsigned int user_vrsave; struct kvm *kvm; unsigned long msr; @@ -4629,14 +4626,7 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu) kvmppc_save_user_regs(); - /* Save userspace EBB and other register values */ - if (cpu_has_feature(CPU_FTR_ARCH_207S)) { - ebb_regs[0] = mfspr(SPRN_EBBHR); - ebb_regs[1] = mfspr(SPRN_EBBRR); - ebb_regs[2] = mfspr(SPRN_BESCR); - user_tar = mfspr(SPRN_TAR); - } - user_vrsave = mfspr(SPRN_VRSAVE); + kvmppc_save_current_sprs(); vcpu->arch.waitp = &vcpu->arch.vcore->wait; vcpu->arch.pgdir = kvm->mm->pgd; @@ -4677,15 +4667,6 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu) } } while (is_kvmppc_resume_guest(r)); - /* Restore userspace EBB and other register values */ - if (cpu_has_feature(CPU_FTR_ARCH_207S)) { - mtspr(SPRN_EBBHR, ebb_regs[0]); - mtspr(SPRN_EBBRR, ebb_regs[1]); - mtspr(SPRN_BESCR, ebb_regs[2]); - mtspr(SPRN_TAR, user_tar); - } - mtspr(SPRN_VRSAVE, user_vrsave); - vcpu->arch.state = KVMPPC_VCPU_NOTREADY; atomic_dec(&kvm->arch.vcpus_running); diff --git a/arch/powerpc/kvm/book3s_hv.h b/arch/powerpc/kvm/book3s_hv.h index d7485b9e9762..6b7f07d9026b 100644 --- a/arch/powerpc/kvm/book3s_hv.h +++ b/arch/powerpc/kvm/book3s_hv.h @@ -4,11 +4,8 @@ * Privileged (non-hypervisor) host registers to save. */ struct p9_host_os_sprs { - unsigned long dscr; - unsigned long tidr; unsigned long iamr; unsigned long amr; - unsigned long fscr; unsigned int pmc1; unsigned int pmc2; diff --git a/arch/powerpc/kvm/book3s_hv_p9_entry.c b/arch/powerpc/kvm/book3s_hv_p9_entry.c index 8499e8a9ca8f..093ac0453d91 100644 --- a/arch/powerpc/kvm/book3s_hv_p9_entry.c +++ b/arch/powerpc/kvm/book3s_hv_p9_entry.c @@ -231,15 +231,26 @@ EXPORT_SYMBOL_GPL(switch_pmu_to_host); static void load_spr_state(struct kvm_vcpu *vcpu, struct p9_host_os_sprs *host_os_sprs) { + /* TAR is very fast */ mtspr(SPRN_TAR, vcpu->arch.tar); +#ifdef CONFIG_ALTIVEC + if (cpu_has_feature(CPU_FTR_ALTIVEC) && + current->thread.vrsave != vcpu->arch.vrsave) + mtspr(SPRN_VRSAVE, vcpu->arch.vrsave); +#endif + if (vcpu->arch.hfscr & HFSCR_EBB) { - mtspr(SPRN_EBBHR, vcpu->arch.ebbhr); - mtspr(SPRN_EBBRR, vcpu->arch.ebbrr); - mtspr(SPRN_BESCR, vcpu->arch.bescr); + if (current->thread.ebbhr != vcpu->arch.ebbhr) + mtspr(SPRN_EBBHR, vcpu->arch.ebbhr); + if (current->thread.ebbrr != vcpu->arch.ebbrr) + mtspr(SPRN_EBBRR, vcpu->arch.ebbrr); + if (current->thread.bescr != vcpu->arch.bescr) + mtspr(SPRN_BESCR, vcpu->arch.bescr); } - if (cpu_has_feature(CPU_FTR_P9_TIDR)) + if (cpu_has_feature(CPU_FTR_P9_TIDR) && + current->thread.tidr != vcpu->arch.tid) mtspr(SPRN_TIDR, vcpu->arch.tid); if (host_os_sprs->iamr != vcpu->arch.iamr) mtspr(SPRN_IAMR, vcpu->arch.iamr); @@ -247,9 +258,9 @@ static void load_spr_state(struct kvm_vcpu *vcpu, mtspr(SPRN_AMR, vcpu->arch.amr); if (vcpu->arch.uamor != 0) mtspr(SPRN_UAMOR, vcpu->arch.uamor); - if (host_os_sprs->fscr != vcpu->arch.fscr) + if (current->thread.fscr != vcpu->arch.fscr) mtspr(SPRN_FSCR, vcpu->arch.fscr); - if (host_os_sprs->dscr != vcpu->arch.dscr) + if (current->thread.dscr != vcpu->arch.dscr) mtspr(SPRN_DSCR, vcpu->arch.dscr); if (vcpu->arch.pspb != 0) mtspr(SPRN_PSPB, vcpu->arch.pspb); @@ -269,20 +280,15 @@ static void store_spr_state(struct kvm_vcpu *vcpu) { vcpu->arch.tar = mfspr(SPRN_TAR); +#ifdef CONFIG_ALTIVEC + if (cpu_has_feature(CPU_FTR_ALTIVEC)) + vcpu->arch.vrsave = mfspr(SPRN_VRSAVE); +#endif + if (vcpu->arch.hfscr & HFSCR_EBB) { vcpu->arch.ebbhr = mfspr(SPRN_EBBHR); vcpu->arch.ebbrr = mfspr(SPRN_EBBRR); vcpu->arch.bescr = mfspr(SPRN_BESCR); - /* - * This is like load_fp in context switching, turn off the - * facility after it wraps the u8 to try avoiding saving - * and restoring the registers each partition switch. - */ - if (!vcpu->arch.nested) { - vcpu->arch.load_ebb++; - if (!vcpu->arch.load_ebb) - vcpu->arch.hfscr &= ~HFSCR_EBB; - } } if (cpu_has_feature(CPU_FTR_P9_TIDR)) @@ -324,7 +330,6 @@ bool load_vcpu_state(struct kvm_vcpu *vcpu, #ifdef CONFIG_ALTIVEC load_vr_state(&vcpu->arch.vr); #endif - mtspr(SPRN_VRSAVE, vcpu->arch.vrsave); return ret; } @@ -338,7 +343,6 @@ void store_vcpu_state(struct kvm_vcpu *vcpu) #ifdef CONFIG_ALTIVEC store_vr_state(&vcpu->arch.vr); #endif - vcpu->arch.vrsave = mfspr(SPRN_VRSAVE); #ifdef CONFIG_PPC_TRANSACTIONAL_MEM if (cpu_has_feature(CPU_FTR_TM) || @@ -364,12 +368,8 @@ EXPORT_SYMBOL_GPL(store_vcpu_state); void save_p9_host_os_sprs(struct p9_host_os_sprs *host_os_sprs) { - if (cpu_has_feature(CPU_FTR_P9_TIDR)) - host_os_sprs->tidr = mfspr(SPRN_TIDR); host_os_sprs->iamr = mfspr(SPRN_IAMR); host_os_sprs->amr = mfspr(SPRN_AMR); - host_os_sprs->fscr = mfspr(SPRN_FSCR); - host_os_sprs->dscr = mfspr(SPRN_DSCR); } EXPORT_SYMBOL_GPL(save_p9_host_os_sprs); @@ -377,26 +377,63 @@ EXPORT_SYMBOL_GPL(save_p9_host_os_sprs); void restore_p9_host_os_sprs(struct kvm_vcpu *vcpu, struct p9_host_os_sprs *host_os_sprs) { + /* + * current->thread.xxx registers must all be restored to host + * values before a potential context switch, othrewise the context + * switch itself will overwrite current->thread.xxx with the values + * from the guest SPRs. + */ + mtspr(SPRN_SPRG_VDSO_WRITE, local_paca->sprg_vdso); - if (cpu_has_feature(CPU_FTR_P9_TIDR)) - mtspr(SPRN_TIDR, host_os_sprs->tidr); + if (cpu_has_feature(CPU_FTR_P9_TIDR) && + current->thread.tidr != vcpu->arch.tid) + mtspr(SPRN_TIDR, current->thread.tidr); if (host_os_sprs->iamr != vcpu->arch.iamr) mtspr(SPRN_IAMR, host_os_sprs->iamr); if (vcpu->arch.uamor != 0) mtspr(SPRN_UAMOR, 0); if (host_os_sprs->amr != vcpu->arch.amr) mtspr(SPRN_AMR, host_os_sprs->amr); - if (host_os_sprs->fscr != vcpu->arch.fscr) - mtspr(SPRN_FSCR, host_os_sprs->fscr); - if (host_os_sprs->dscr != vcpu->arch.dscr) - mtspr(SPRN_DSCR, host_os_sprs->dscr); + if (current->thread.fscr != vcpu->arch.fscr) + mtspr(SPRN_FSCR, current->thread.fscr); + if (current->thread.dscr != vcpu->arch.dscr) + mtspr(SPRN_DSCR, current->thread.dscr); if (vcpu->arch.pspb != 0) mtspr(SPRN_PSPB, 0); /* Save guest CTRL register, set runlatch to 1 */ if (!(vcpu->arch.ctrl & 1)) mtspr(SPRN_CTRLT, 1); + +#ifdef CONFIG_ALTIVEC + if (cpu_has_feature(CPU_FTR_ALTIVEC) && + vcpu->arch.vrsave != current->thread.vrsave) + mtspr(SPRN_VRSAVE, current->thread.vrsave); +#endif + if (vcpu->arch.hfscr & HFSCR_EBB) { + if (vcpu->arch.bescr != current->thread.bescr) + mtspr(SPRN_BESCR, current->thread.bescr); + if (vcpu->arch.ebbhr != current->thread.ebbhr) + mtspr(SPRN_EBBHR, current->thread.ebbhr); + if (vcpu->arch.ebbrr != current->thread.ebbrr) + mtspr(SPRN_EBBRR, current->thread.ebbrr); + + if (!vcpu->arch.nested) { + /* + * This is like load_fp in context switching, turn off + * the facility after it wraps the u8 to try avoiding + * saving and restoring the registers each partition + * switch. + */ + vcpu->arch.load_ebb++; + if (!vcpu->arch.load_ebb) + vcpu->arch.hfscr &= ~HFSCR_EBB; + } + } + + if (vcpu->arch.tar != current->thread.tar) + mtspr(SPRN_TAR, current->thread.tar); } EXPORT_SYMBOL_GPL(restore_p9_host_os_sprs);