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authorAlexander Graf <graf@amazon.com>2022-05-10 14:37:17 +0200
committerMichael Ellerman <mpe@ellerman.id.au>2022-05-11 23:03:16 +1000
commitee8348496c77e3737d0a6cda307a521f2cff954f (patch)
tree4221c64fa85554adbf94dd10253fd0769a8fb9ee /arch/powerpc/kvm
parent348c71344111d7a48892e3e52264ff11956fc196 (diff)
downloadlinux-ee8348496c77e3737d0a6cda307a521f2cff954f.tar.bz2
KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context()
Commit 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C") moved the switch_mmu_context() to C. While in principle a good idea, it meant that the function now uses the stack. The stack is not accessible from real mode though. So to keep calling the function, let's turn on MSR_DR while we call it. That way, all pointer references to the stack are handled virtually. In addition, make sure to save/restore r12 on the stack, as it may get clobbered by the C function. Fixes: 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C") Cc: stable@vger.kernel.org # v5.14+ Reported-by: Matt Evans <matt@ozlabs.org> Signed-off-by: Alexander Graf <graf@amazon.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20220510123717.24508-1-graf@amazon.com
Diffstat (limited to 'arch/powerpc/kvm')
-rw-r--r--arch/powerpc/kvm/book3s_32_sr.S26
1 files changed, 21 insertions, 5 deletions
diff --git a/arch/powerpc/kvm/book3s_32_sr.S b/arch/powerpc/kvm/book3s_32_sr.S
index e3ab9df6cf19..6cfcd20d4668 100644
--- a/arch/powerpc/kvm/book3s_32_sr.S
+++ b/arch/powerpc/kvm/book3s_32_sr.S
@@ -122,11 +122,27 @@
/* 0x0 - 0xb */
- /* 'current->mm' needs to be in r4 */
- tophys(r4, r2)
- lwz r4, MM(r4)
- tophys(r4, r4)
- /* This only clobbers r0, r3, r4 and r5 */
+ /* switch_mmu_context() needs paging, let's enable it */
+ mfmsr r9
+ ori r11, r9, MSR_DR
+ mtmsr r11
+ sync
+
+ /* switch_mmu_context() clobbers r12, rescue it */
+ SAVE_GPR(12, r1)
+
+ /* Calling switch_mmu_context(<inv>, current->mm, <inv>); */
+ lwz r4, MM(r2)
bl switch_mmu_context
+ /* restore r12 */
+ REST_GPR(12, r1)
+
+ /* Disable paging again */
+ mfmsr r9
+ li r6, MSR_DR
+ andc r9, r9, r6
+ mtmsr r9
+ sync
+
.endm