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>
diff --git a/arch/powerpc/kvm/book3s_64_slb.S b/arch/powerpc/kvm/book3s_64_slb.S
index 8e44788..7188c11 100644
--- a/arch/powerpc/kvm/book3s_64_slb.S
+++ b/arch/powerpc/kvm/book3s_64_slb.S
@@ -51,24 +51,18 @@
*
* 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 @@
/* Enter guest */
- mfspr r0, SPRN_SPRG_SCRATCH0
+ 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)
- 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)
+ 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 @@
/* 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 @@
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 @@
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: