Using the hash MMU on P7+, the AMR is used for pkeys. It's important that the host and guest never end up with each other's AMR value, since this could disrupt operations and break things.
The AMR gets correctly restored on context switch, however before this happens (i.e. in a program like qemu) having the host value of the AMR be zero would interfere with that program using pkeys.
In addition, the AMR on Radix can control kernel access to userspace data, which you wouldn't want to be zeroed.
So, just save and restore it like the other registers that get saved and restored.
Fixes: cf43d3b26452 ("powerpc: Enable pkey subsystem") Cc: stable@vger.kernel.org # v4.16+ Signed-off-by: Russell Currey ruscur@russell.cc --- I'm not entirely sure the stack frame numbers are correct, I've tested it and it works but it'd be good if someone could double check this.
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index 9b8d50a7cbaf..6291751c4ad9 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -47,7 +47,7 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300) #define NAPPING_NOVCPU 2
/* Stack frame offsets for kvmppc_hv_entry */ -#define SFS 208 +#define SFS 224 /* must be divisible by 16 */ #define STACK_SLOT_TRAP (SFS-4) #define STACK_SLOT_SHORT_PATH (SFS-8) #define STACK_SLOT_TID (SFS-16) @@ -58,8 +58,9 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300) #define STACK_SLOT_DAWR (SFS-56) #define STACK_SLOT_DAWRX (SFS-64) #define STACK_SLOT_HFSCR (SFS-72) +#define STACK_SLOT_AMR (SFS-80) /* the following is used by the P9 short path */ -#define STACK_SLOT_NVGPRS (SFS-152) /* 18 gprs */ +#define STACK_SLOT_NVGPRS (SFS-160) /* 18 gprs */
/* * Call kvmppc_hv_entry in real mode. @@ -743,6 +744,9 @@ BEGIN_FTR_SECTION std r7, STACK_SLOT_DAWRX(r1) END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
+ mfspr r5, SPRN_AMR + std r5, STACK_SLOT_AMR(r1) + BEGIN_FTR_SECTION /* Set partition DABR */ /* Do this before re-enabling PMU to avoid P7 DABR corruption bug */ @@ -1640,13 +1644,14 @@ BEGIN_FTR_SECTION END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300) 8:
- /* Save and reset AMR and UAMOR before turning on the MMU */ + /* Save and restore/reset AMR and UAMOR before turning on the MMU */ mfspr r5,SPRN_AMR mfspr r6,SPRN_UAMOR std r5,VCPU_AMR(r9) std r6,VCPU_UAMOR(r9) + ld r5,STACK_SLOT_AMR(r1) li r6,0 - mtspr SPRN_AMR,r6 + mtspr SPRN_AMR, r5 mtspr SPRN_UAMOR, r6
/* Switch DSCR back to host value */