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Date: Mon, 16 May 2022 21:36:46 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Matt Evans <matt@...abs.org>, Alexander Graf <graf@...zon.com>, Michael Ellerman <mpe@...erman.id.au> Subject: [PATCH 5.17 072/114] KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context() From: Alexander Graf <graf@...zon.com> 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@...r.kernel.org # v5.14+ Reported-by: Matt Evans <matt@...abs.org> Signed-off-by: Alexander Graf <graf@...zon.com> Signed-off-by: Michael Ellerman <mpe@...erman.id.au> Link: https://lore.kernel.org/r/20220510123717.24508-1-graf@amazon.com Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- 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
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