From cda4a14733138b8f15b0b69d97ec198dc41eccae Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Thu, 22 Mar 2018 09:48:54 +1100 Subject: [PATCH] KVM: PPC: Book3S HV: Fix duplication of host SLB entries Since commit 6964e6a4e489 ("KVM: PPC: Book3S HV: Do SLB load/unload with guest LPCR value loaded", 2018-01-11), we have been seeing occasional machine check interrupts on POWER8 systems when running KVM guests, due to SLB multihit errors. This turns out to be due to the guest exit code reloading the host SLB entries from the SLB shadow buffer when the SLB was not previously cleared in the guest entry path. This can happen because the path which skips from the guest entry code to the guest exit code without entering the guest now does the skip before the SLB is cleared and loaded with guest values, but the host values are loaded after the point in the guest exit path that we skip to. To fix this, we move the code that reloads the host SLB values up so that it occurs just before the point in the guest exit code (the label guest_bypass:) where we skip to from the guest entry path. Reported-by: Alexey Kardashevskiy Fixes: 6964e6a4e489 ("KVM: PPC: Book3S HV: Do SLB load/unload with guest LPCR value loaded") Tested-by: Alexey Kardashevskiy Signed-off-by: Paul Mackerras --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 35 +++++++++++++------------ 1 file changed, 18 insertions(+), 17 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index d33264697a31..f86a20270e50 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -1557,6 +1557,24 @@ mc_cont: ptesync 3: stw r5,VCPU_SLB_MAX(r9) + /* load host SLB entries */ +BEGIN_MMU_FTR_SECTION + b 0f +END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX) + ld r8,PACA_SLBSHADOWPTR(r13) + + .rept SLB_NUM_BOLTED + li r3, SLBSHADOW_SAVEAREA + LDX_BE r5, r8, r3 + addi r3, r3, 8 + LDX_BE r6, r8, r3 + andis. r7,r5,SLB_ESID_V@h + beq 1f + slbmte r6,r5 +1: addi r8,r8,16 + .endr +0: + guest_bypass: stw r12, STACK_SLOT_TRAP(r1) mr r3, r12 @@ -2018,23 +2036,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) mtspr SPRN_LPCR,r8 isync 48: - /* load host SLB entries */ -BEGIN_MMU_FTR_SECTION - b 0f -END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX) - ld r8,PACA_SLBSHADOWPTR(r13) - - .rept SLB_NUM_BOLTED - li r3, SLBSHADOW_SAVEAREA - LDX_BE r5, r8, r3 - addi r3, r3, 8 - LDX_BE r6, r8, r3 - andis. r7,r5,SLB_ESID_V@h - beq 1f - slbmte r6,r5 -1: addi r8,r8,16 - .endr -0: #ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING /* Finish timing, if we have a vcpu */ ld r4, HSTATE_KVM_VCPU(r13)