powerpc fixes for 5.18 #5

- Fix KVM PR on 32-bit, which was broken by some MMU code refactoring.
 
 Thanks to: Alexander Graf, Matt Evans.
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Merge tag 'powerpc-5.18-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fix from Michael Ellerman:

 - Fix KVM PR on 32-bit, which was broken by some MMU code refactoring.

Thanks to: Alexander Graf, and Matt Evans.

* tag 'powerpc-5.18-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context()

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