From: Michael Neuling <mikey@neuling.org>
Date: Fri, 15 Sep 2017 15:26:14 +1000
Subject: KVM: PPC: Book3S HV: Check for updated HDSISR on P9 HDSI exception
Patch-mainline: v4.14-rc3
Git-commit: e001fa78d44d0b5c7b1498d1e4a038740efa3b1e
References: bsc#1077761
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>
Acked-by: Alexander Graf <agraf@suse.de>
---
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1122,6 +1122,13 @@
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)
@@ -1958,9 +1965,14 @@
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