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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 <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-39-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2021-11-23 19:52:16 +10:00 committed by Michael Ellerman
parent 022ecb960c
commit 5236756d04
5 changed files with 73 additions and 51 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/powerpc/include/asm/switch_to.h
View File

@ -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);

6
arch/powerpc/kernel/process.c
View File

@ -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(&current->thread);
}
EXPORT_SYMBOL_GPL(kvmppc_save_current_sprs);
#endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
static inline void restore_sprs(struct thread_struct *old_thread,

21
arch/powerpc/kvm/book3s_hv.c
View File

@ -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);

3
arch/powerpc/kvm/book3s_hv.h
View File

@ -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;

93
arch/powerpc/kvm/book3s_hv_p9_entry.c
View File

@ -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);