KVM: PPC: Use PACA backed shadow vcpu

We're being horribly racy right now. All the entry and exit code hijacks
random fields from the PACA that could easily be used by different code in
case we get interrupted, for example by a #MC or even page fault.

After discussing this with Ben, we figured it's best to reserve some more
space in the PACA and just shove off some vcpu state to there.

That way we can drastically improve the readability of the code, make it
less racy and less complex.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 90 insertions, 60 deletions

diff --git a/arch/powerpc/kvm/book3s_64_slb.S b/arch/powerpc/kvm/book3s_64_slb.S
index 8e447886666..7188c11ed7d 100644
--- a/arch/powerpc/kvm/book3s_64_slb.S
+++ b/arch/powerpc/kvm/book3s_64_slb.S
@@ -51,24 +51,18 @@ kvmppc_handler_trampoline_enter:
 	 *
 	 * MSR = ~IR|DR
 	 * R13 = PACA
+	 * R1 = host R1
+	 * R2 = host R2
 	 * R9 = guest IP
 	 * R10 = guest MSR
-	 * R11 = free
-	 * R12 = free
-	 * PACA[PACA_EXMC + EX_R9] = guest R9
-	 * PACA[PACA_EXMC + EX_R10] = guest R10
-	 * PACA[PACA_EXMC + EX_R11] = guest R11
-	 * PACA[PACA_EXMC + EX_R12] = guest R12
-	 * PACA[PACA_EXMC + EX_R13] = guest R13
-	 * PACA[PACA_EXMC + EX_CCR] = guest CR
-	 * PACA[PACA_EXMC + EX_R3] = guest XER
+	 * all other GPRS = free
+	 * PACA[KVM_CR] = guest CR
+	 * PACA[KVM_XER] = guest XER
 	 */
 
 	mtsrr0	r9
 	mtsrr1	r10
 
-	mtspr	SPRN_SPRG_SCRATCH0, r0
-
 	/* Remove LPAR shadow entries */
 
 #if SLB_NUM_BOLTED == 3
@@ -131,20 +125,27 @@ slb_do_enter:
 
 	/* Enter guest */
 
-	mfspr	r0, SPRN_SPRG_SCRATCH0
-
-	ld	r9, (PACA_EXMC+EX_R9)(r13)
-	ld	r10, (PACA_EXMC+EX_R10)(r13)
-	ld	r12, (PACA_EXMC+EX_R12)(r13)
-
-	lwz	r11, (PACA_EXMC+EX_CCR)(r13)
+	ld	r0, (PACA_KVM_R0)(r13)
+	ld	r1, (PACA_KVM_R1)(r13)
+	ld	r2, (PACA_KVM_R2)(r13)
+	ld	r3, (PACA_KVM_R3)(r13)
+	ld	r4, (PACA_KVM_R4)(r13)
+	ld	r5, (PACA_KVM_R5)(r13)
+	ld	r6, (PACA_KVM_R6)(r13)
+	ld	r7, (PACA_KVM_R7)(r13)
+	ld	r8, (PACA_KVM_R8)(r13)
+	ld	r9, (PACA_KVM_R9)(r13)
+	ld	r10, (PACA_KVM_R10)(r13)
+	ld	r12, (PACA_KVM_R12)(r13)
+
+	lwz	r11, (PACA_KVM_CR)(r13)
 	mtcr	r11
 
-	ld	r11, (PACA_EXMC+EX_R3)(r13)
+	ld	r11, (PACA_KVM_XER)(r13)
 	mtxer	r11
 
-	ld	r11, (PACA_EXMC+EX_R11)(r13)
-	ld	r13, (PACA_EXMC+EX_R13)(r13)
+	ld	r11, (PACA_KVM_R11)(r13)
+	ld	r13, (PACA_KVM_R13)(r13)
 
 	RFI
 kvmppc_handler_trampoline_enter_end:
@@ -162,28 +163,58 @@ kvmppc_handler_trampoline_exit:
 
 	/* Register usage at this point:
 	 *
-	 * SPRG_SCRATCH0 = guest R13
-	 * R01           = host R1
-	 * R02           = host R2
-	 * R10           = guest PC
-	 * R11           = guest MSR
-	 * R12           = exit handler id
-	 * R13           = PACA
-	 * PACA.exmc.CCR  = guest CR
-	 * PACA.exmc.R9  = guest R1
-	 * PACA.exmc.R10 = guest R10
-	 * PACA.exmc.R11 = guest R11
-	 * PACA.exmc.R12 = guest R12
-	 * PACA.exmc.R13 = guest R2
+	 * SPRG_SCRATCH0     = guest R13
+	 * R12               = exit handler id
+	 * R13               = PACA
+	 * PACA.KVM.SCRATCH0 = guest R12
+	 * PACA.KVM.SCRATCH1 = guest CR
 	 *
 	 */
 
 	/* Save registers */
 
-	std	r0, (PACA_EXMC+EX_SRR0)(r13)
-	std	r9, (PACA_EXMC+EX_R3)(r13)
-	std	r10, (PACA_EXMC+EX_LR)(r13)
-	std	r11, (PACA_EXMC+EX_DAR)(r13)
+	std	r0, PACA_KVM_R0(r13)
+	std	r1, PACA_KVM_R1(r13)
+	std	r2, PACA_KVM_R2(r13)
+	std	r3, PACA_KVM_R3(r13)
+	std	r4, PACA_KVM_R4(r13)
+	std	r5, PACA_KVM_R5(r13)
+	std	r6, PACA_KVM_R6(r13)
+	std	r7, PACA_KVM_R7(r13)
+	std	r8, PACA_KVM_R8(r13)
+	std	r9, PACA_KVM_R9(r13)
+	std	r10, PACA_KVM_R10(r13)
+	std	r11, PACA_KVM_R11(r13)
+
+	/* Restore R1/R2 so we can handle faults */
+	ld	r1, PACA_KVM_HOST_R1(r13)
+	ld	r2, PACA_KVM_HOST_R2(r13)
+
+	/* Save guest PC and MSR in GPRs */
+	mfsrr0	r3
+	mfsrr1	r4
+
+	/* Get scratch'ed off registers */
+	mfspr	r9, SPRN_SPRG_SCRATCH0
+	std	r9, PACA_KVM_R13(r13)
+
+	ld	r8, PACA_KVM_SCRATCH0(r13)
+	std	r8, PACA_KVM_R12(r13)
+
+	lwz	r7, PACA_KVM_SCRATCH1(r13)
+	stw	r7, PACA_KVM_CR(r13)
+
+	/* Save more register state  */
+
+	mfxer	r6
+	stw	r6, PACA_KVM_XER(r13)
+
+	mfdar	r5
+	mfdsisr	r6
+
+	/* Unset guest state */
+	li	r9, 0
+	stb	r9, PACA_KVM_IN_GUEST(r13)
 
 	/*
 	 * In order for us to easily get the last instruction,
@@ -207,7 +238,8 @@ ld_last_inst:
 	ori	r11, r9, MSR_DR			/* Enable paging for data */
 	mtmsr	r11
 	/*    2) fetch the instruction */
-	lwz	r0, 0(r10)
+	/* XXX implement PACA_KVM_IN_GUEST=2 path to safely jump over this */
+	lwz	r0, 0(r3)
 	/*    3) disable paging again */
 	mtmsr	r9
 
@@ -233,29 +265,27 @@ no_ld_last_inst:
 
 slb_do_exit:
 
-	/* Restore registers */
-
-	ld	r11, (PACA_EXMC+EX_DAR)(r13)
-	ld	r10, (PACA_EXMC+EX_LR)(r13)
-	ld	r9, (PACA_EXMC+EX_R3)(r13)
-
-	/* Save last inst */
-	stw	r0, (PACA_EXMC+EX_LR)(r13)
-
-	/* Save DAR and DSISR before going to paged mode */
-	mfdar	r0
-	std	r0, (PACA_EXMC+EX_DAR)(r13)
-	mfdsisr	r0
-	stw	r0, (PACA_EXMC+EX_DSISR)(r13)
+	/* Register usage at this point:
+	 *
+	 * R0         = guest last inst
+	 * R1         = host R1
+	 * R2         = host R2
+	 * R3         = guest PC
+	 * R4         = guest MSR
+	 * R5         = guest DAR
+	 * R6         = guest DSISR
+	 * R12        = exit handler id
+	 * R13        = PACA
+	 * PACA.KVM.* = guest *
+	 *
+	 */
 
 	/* RFI into the highmem handler */
-	mfmsr	r0
-	ori	r0, r0, MSR_IR|MSR_DR|MSR_RI	/* Enable paging */
-	mtsrr1	r0
-	ld	r0, PACASAVEDMSR(r13)		/* Highmem handler address */
-	mtsrr0	r0
-
-	mfspr	r0, SPRN_SPRG_SCRATCH0
+	mfmsr	r7
+	ori	r7, r7, MSR_IR|MSR_DR|MSR_RI	/* Enable paging */
+	mtsrr1	r7
+	ld	r8, PACA_KVM_VMHANDLER(r13)	/* Highmem handler address */
+	mtsrr0	r8
 
 	RFI
 kvmppc_handler_trampoline_exit_end: