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 8e4478866669..7188c11ed7d1 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: