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.
-61 cycles (6620) POWER9 virt-mode NULL hcall
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
---
arch/powerpc/include/asm/switch_to.h | 2 +
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, 74 insertions(+), 51 deletions(-)
diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
index 9d1fbd8be1c7..de17c45314bc 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -112,6 +112,8 @@ static inline void clear_task_ebb(struct task_struct *t)
#endif
}
+void kvmppc_save_current_sprs(void);
+
extern int set_thread_tidr(struct task_struct *t);
#endif /* _ASM_POWERPC_SWITCH_TO_H */
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 00b55b38a460..d54baa3e20d2 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1180,6 +1180,12 @@ static inline void save_sprs(struct thread_struct *t)
#endif
}
+void kvmppc_save_current_sprs(void)
+{
+ save_sprs(¤t->thread);
+}
+EXPORT_SYMBOL_GPL(kvmppc_save_current_sprs);
+
static inline void restore_sprs(struct thread_struct *old_thread,
struct thread_struct *new_thread)
{
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 5b2114c00c43..c0a04ce39e00 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -4510,9 +4510,6 @@ 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;
@@ -4573,14 +4570,7 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu)
save_user_regs_kvm();
- /* 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;
@@ -4621,15 +4611,6 @@ 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 a9065a380547..04884e271862 100644
--- a/arch/powerpc/kvm/book3s_hv.h
+++ b/arch/powerpc/kvm/book3s_hv.h
@@ -3,11 +3,8 @@
* 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 db5eb83e26d1..5fca0a09425d 100644
--- a/arch/powerpc/kvm/book3s_hv_p9_entry.c
+++ b/arch/powerpc/kvm/book3s_hv_p9_entry.c
@@ -223,15 +223,26 @@ 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_ARCH_31))
+ if (!cpu_has_feature(CPU_FTR_ARCH_31) &&
+ 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);
@@ -239,9 +250,9 @@ 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);
@@ -261,20 +272,15 @@ 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_ARCH_31))
@@ -315,7 +321,6 @@ 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;
}
@@ -329,7 +334,6 @@ void store_vcpu_state(struct kvm_vcpu *vcpu)
#ifdef CONFIG_ALTIVEC
store_vr_state(&vcpu->arch.vr);
#endif
- vcpu->arch.vrsave = mfspr(SPRN_VRSAVE);
if ((cpu_has_feature(CPU_FTR_TM) ||
cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST)) &&
@@ -354,12 +358,8 @@ 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_ARCH_31))
- 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);
@@ -367,26 +367,63 @@ 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_ARCH_31))
- mtspr(SPRN_TIDR, host_os_sprs->tidr);
+ if (!cpu_has_feature(CPU_FTR_ARCH_31) &&
+ 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);
--
2.23.0
