Commit ee834849 authored by Alexander Graf's avatar Alexander Graf Committed by Michael Ellerman
Browse files

KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context() 



Commit 863771a2 ("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: 863771a2 ("powerpc/32s: Convert switch_mmu_context() to C")
Cc: stable@vger.kernel.org # v5.14+
Reported-by: default avatarMatt Evans <matt@ozlabs.org>
Signed-off-by: default avatarAlexander Graf <graf@amazon.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220510123717.24508-1-graf@amazon.com
parent 348c7134

arch/powerpc/kvm/book3s_32_sr.S

+21 −5
Original line number Diff line number Diff line
@@ -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