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authorMichael Neuling <mikey@neuling.org>2017-09-15 15:26:14 +1000
committerPaolo Bonzini <pbonzini@redhat.com>2017-09-22 10:45:46 +0200
commite001fa78d44d0b5c7b1498d1e4a038740efa3b1e (patch)
tree2e9f3888f00ccfeb4ad997bdafbadd7ad1810dfe
parent44889942b6eb356eab27ce25fe10701adfec7776 (diff)
KVM: PPC: Book3S HV: Check for updated HDSISR on P9 HDSI exception
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>
-rw-r--r--arch/powerpc/kvm/book3s_hv_rmhandlers.S14
1 files changed, 13 insertions, 1 deletions
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 17936f82d3c7..ec69fa45d5a2 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -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