KVM: PPC: Book3S HV: Fix register usage when loading/saving VRSAVE

Commit 595e4f7e697e ("KVM: PPC: Book3S HV: Use load/store_fp_state
functions in HV guest entry/exit") changed the register usage in
kvmppc_save_fp() and kvmppc_load_fp() but omitted changing the
instructions that load and save VRSAVE.  The result is that the
VRSAVE value was loaded from a constant address, and saved to a
location past the end of the vcpu struct, causing host kernel
memory corruption and various kinds of host kernel crashes.

This fixes the problem by using register r31, which contains the
vcpu pointer, instead of r3 and r4.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 781e6bf69afb..818dce344e82 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -2136,7 +2136,7 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 #endif
         mfspr   r6,SPRN_VRSAVE
-        stw     r6,VCPU_VRSAVE(r3)
+        stw     r6,VCPU_VRSAVE(r31)
         mtlr    r30
         mtmsrd  r5
         isync
@@ -2173,7 +2173,7 @@ BEGIN_FTR_SECTION
         bl      .load_vr_state
 END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 #endif
-        lwz     r7,VCPU_VRSAVE(r4)
+        lwz     r7,VCPU_VRSAVE(r31)
         mtspr   SPRN_VRSAVE,r7
         mtlr    r30
         mr      r4,r31