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KVM: PPC: Book3S HV Nested: Reflect guest PMU in-use to L0 when guest SPRs are live

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After the L1 saves its PMU SPRs but before loading the L2's PMU SPRs,
switch the pmcregs_in_use field in the L1 lppaca to the value advertised
by the L2 in its VPA. On the way out of the L2, set it back after saving
the L2 PMU registers (if they were in-use).

This transfers the PMU liveness indication between the L1 and L2 at the
points where the registers are not live.

This fixes the nested HV bug for which a workaround was added to the L0
HV by commit 63279eeb7f ("KVM: PPC: Book3S HV: Always save guest pmu
for guest capable of nesting"), which explains the problem in detail.
That workaround is no longer required for guests that include this bug
fix.

Fixes: 360cae3137 ("KVM: PPC: Book3S HV: Nested guest entry via hypercall")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Link: https://lore.kernel.org/r/20210811160134.904987-10-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2021-08-12 02:00:43 +10:00 committed by Michael Ellerman
parent f2e29db156
commit 1782663897
2 changed files with 27 additions and 0 deletions
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7
arch/powerpc/include/asm/pmc.h
View File

@ -34,6 +34,13 @@ static inline void ppc_set_pmu_inuse(int inuse)
#endif
}
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
static inline int ppc_get_pmu_inuse(void)
{
return get_paca()->pmcregs_in_use;
}
#endif
extern void power4_enable_pmcs(void);
#else /* CONFIG_PPC64 */

20
arch/powerpc/kvm/book3s_hv.c
View File

@ -59,6 +59,7 @@
#include <asm/kvm_book3s.h>
#include <asm/mmu_context.h>
#include <asm/lppaca.h>
#include <asm/pmc.h>
#include <asm/processor.h>
#include <asm/cputhreads.h>
#include <asm/page.h>
@ -3891,6 +3892,18 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST))
kvmppc_restore_tm_hv(vcpu, vcpu->arch.shregs.msr, true);
#ifdef CONFIG_PPC_PSERIES
if (kvmhv_on_pseries()) {
barrier();
if (vcpu->arch.vpa.pinned_addr) {
struct lppaca *lp = vcpu->arch.vpa.pinned_addr;
get_lppaca()->pmcregs_in_use = lp->pmcregs_in_use;
} else {
get_lppaca()->pmcregs_in_use = 1;
}
barrier();
}
#endif
kvmhv_load_guest_pmu(vcpu);
msr_check_and_set(MSR_FP | MSR_VEC | MSR_VSX);
@ -4025,6 +4038,13 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
save_pmu |= nesting_enabled(vcpu->kvm);
kvmhv_save_guest_pmu(vcpu, save_pmu);
#ifdef CONFIG_PPC_PSERIES
if (kvmhv_on_pseries()) {
barrier();
get_lppaca()->pmcregs_in_use = ppc_get_pmu_inuse();
barrier();
}
#endif
vc->entry_exit_map = 0x101;
vc->in_guest = 0;