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KVM: PPC: Book3S HV: Check for updated HDSISR on P9 HDSI exception

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On POWER9 DD2.1 and below, sometimes on a Hypervisor Data Storage
Interrupt (HDSI) the HDSISR is not be updated at all.

To work around this we put a canary value into the HDSISR before
returning to a guest and then check for this canary when we take a
HDSI. If we find the canary on a HDSI, we know the hardware didn't
update the HDSISR. In this case we return to the guest to retake the
HDSI which should correctly update the HDSISR the second time HDSI
entry.

After talking to Paulus we've applied this workaround to all POWER9
CPUs. The workaround of returning to the guest shouldn't ever be
triggered on well behaving CPU. The extra instructions should have
negligible performance impact.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Michael Neuling 2017-09-15 15:26:14 +10:00 committed by Paolo Bonzini
parent 44889942b6
commit e001fa78d4
1 changed files with 13 additions and 1 deletions
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14
arch/powerpc/kvm/book3s_hv_rmhandlers.S
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@ -1121,6 +1121,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
BEGIN_FTR_SECTION
mtspr SPRN_PPR, r0
END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
/* Move canary into DSISR to check for later */
BEGIN_FTR_SECTION
li r0, 0x7fff
mtspr SPRN_HDSISR, r0
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
ld r0, VCPU_GPR(R0)(r4)
ld r4, VCPU_GPR(R4)(r4)
@ -1956,9 +1963,14 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX)
kvmppc_hdsi:
ld r3, VCPU_KVM(r9)
lbz r0, KVM_RADIX(r3)
cmpwi r0, 0
mfspr r4, SPRN_HDAR
mfspr r6, SPRN_HDSISR
BEGIN_FTR_SECTION
/* Look for DSISR canary. If we find it, retry instruction */
cmpdi r6, 0x7fff
beq 6f
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
cmpwi r0, 0
bne .Lradix_hdsi /* on radix, just save DAR/DSISR/ASDR */
/* HPTE not found fault or protection fault? */
andis. r0, r6, (DSISR_NOHPTE | DSISR_PROTFAULT)@h