This is a note to let you know that I've just added the patch titled KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context() to the 5.17-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-ppc-book3s-pr-enable-msr_dr-for-switch_mmu_context.patch and it can be found in the queue-5.17 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From ee8348496c77e3737d0a6cda307a521f2cff954f Mon Sep 17 00:00:00 2001 From: Alexander Graf <graf@xxxxxxxxxx> Date: Tue, 10 May 2022 14:37:17 +0200 Subject: KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context() From: Alexander Graf <graf@xxxxxxxxxx> commit ee8348496c77e3737d0a6cda307a521f2cff954f upstream. 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@xxxxxxxxxxxxxxx # v5.14+ Reported-by: Matt Evans <matt@xxxxxxxxxx> Signed-off-by: Alexander Graf <graf@xxxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220510123717.24508-1-graf@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/powerpc/kvm/book3s_32_sr.S | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) --- 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 Patches currently in stable-queue which might be from graf@xxxxxxxxxx are queue-5.17/kvm-ppc-book3s-pr-enable-msr_dr-for-switch_mmu_context.patch