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KVM: PPC: Book3S HV P9: Read machine check registers while MSR[RI] is 0

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SRR0/1, DAR, DSISR must all be protected from machine check which can
clobber them. Ensure MSR[RI] is clear while they are live.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210528090752.3542186-17-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2021-05-28 19:07:36 +10:00 committed by Michael Ellerman
parent c00366e237
commit 6d770e3fe9
2 changed files with 39 additions and 5 deletions
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11
arch/powerpc/kvm/book3s_hv.c
View file

@ -3571,11 +3571,16 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
mtspr(SPRN_BESCR, vcpu->arch.bescr);
mtspr(SPRN_WORT, vcpu->arch.wort);
mtspr(SPRN_TIDR, vcpu->arch.tid);
mtspr(SPRN_DAR, vcpu->arch.shregs.dar);
mtspr(SPRN_DSISR, vcpu->arch.shregs.dsisr);
mtspr(SPRN_AMR, vcpu->arch.amr);
mtspr(SPRN_UAMOR, vcpu->arch.uamor);
/*
* DAR, DSISR, and for nested HV, SPRGs must be set with MSR[RI]
* clear (or hstate set appropriately to catch those registers
* being clobbered if we take a MCE or SRESET), so those are done
* later.
*/
if (!(vcpu->arch.ctrl & 1))
mtspr(SPRN_CTRLT, mfspr(SPRN_CTRLF) & ~1);
@ -3618,6 +3623,8 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
hvregs.vcpu_token = vcpu->vcpu_id;
}
hvregs.hdec_expiry = time_limit;
mtspr(SPRN_DAR, vcpu->arch.shregs.dar);
mtspr(SPRN_DSISR, vcpu->arch.shregs.dsisr);
trap = plpar_hcall_norets(H_ENTER_NESTED, __pa(&hvregs),
__pa(&vcpu->arch.regs));
kvmhv_restore_hv_return_state(vcpu, &hvregs);

33
arch/powerpc/kvm/book3s_hv_p9_entry.c
View file

@ -122,6 +122,7 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
s64 hdec;
u64 tb, purr, spurr;
u64 *exsave;
bool ri_set;
unsigned long msr = mfmsr();
int trap;
unsigned long host_hfscr = mfspr(SPRN_HFSCR);
@ -192,9 +193,6 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
*/
mtspr(SPRN_HDEC, hdec);
mtspr(SPRN_SRR0, vcpu->arch.shregs.srr0);
mtspr(SPRN_SRR1, vcpu->arch.shregs.srr1);
start_timing(vcpu, &vcpu->arch.rm_entry);
vcpu->arch.ceded = 0;
@ -220,6 +218,13 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
*/
mtspr(SPRN_HDSISR, HDSISR_CANARY);
__mtmsrd(0, 1); /* clear RI */
mtspr(SPRN_DAR, vcpu->arch.shregs.dar);
mtspr(SPRN_DSISR, vcpu->arch.shregs.dsisr);
mtspr(SPRN_SRR0, vcpu->arch.shregs.srr0);
mtspr(SPRN_SRR1, vcpu->arch.shregs.srr1);
accumulate_time(vcpu, &vcpu->arch.guest_time);
local_paca->kvm_hstate.in_guest = KVM_GUEST_MODE_HV_FAST;
@ -237,7 +242,13 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
/* 0x2 bit for HSRR is only used by PR and P7/8 HV paths, clear it */
trap = local_paca->kvm_hstate.scratch0 & ~0x2;
/* HSRR interrupts leave MSR[RI] unchanged, SRR interrupts clear it. */
ri_set = false;
if (likely(trap > BOOK3S_INTERRUPT_MACHINE_CHECK)) {
if (trap != BOOK3S_INTERRUPT_SYSCALL &&
(vcpu->arch.shregs.msr & MSR_RI))
ri_set = true;
exsave = local_paca->exgen;
} else if (trap == BOOK3S_INTERRUPT_SYSTEM_RESET) {
exsave = local_paca->exnmi;
@ -247,6 +258,22 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
vcpu->arch.regs.gpr[1] = local_paca->kvm_hstate.scratch1;
vcpu->arch.regs.gpr[3] = local_paca->kvm_hstate.scratch2;
/*
* Only set RI after reading machine check regs (DAR, DSISR, SRR0/1)
* and hstate scratch (which we need to move into exsave to make
* re-entrant vs SRESET/MCE)
*/
if (ri_set) {
if (unlikely(!(mfmsr() & MSR_RI))) {
__mtmsrd(MSR_RI, 1);
WARN_ON_ONCE(1);
}
} else {
WARN_ON_ONCE(mfmsr() & MSR_RI);
__mtmsrd(MSR_RI, 1);
}
vcpu->arch.regs.gpr[9] = exsave[EX_R9/sizeof(u64)];
vcpu->arch.regs.gpr[10] = exsave[EX_R10/sizeof(u64)];
vcpu->arch.regs.gpr[11] = exsave[EX_R11/sizeof(u64)];