KVM: PPC: Use get/set for to_svcpu to help preemption

When running the 64-bit Book3s PR code without CONFIG_PREEMPT_NONE, we were
doing a few things wrong, most notably access to PACA fields without making
sure that the pointers stay stable accross the access (preempt_disable()).

This patch moves to_svcpu towards a get/put model which allows us to disable
preemption while accessing the shadow vcpu fields in the PACA. That way we
can run preemptible and everyone's happy!

Reported-by: Jörg Sommer <joerg@alea.gnuu.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 42 insertions, 20 deletions

diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 857ecde0cfdf..0c31507be908 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -56,10 +56,12 @@ static int kvmppc_handle_ext(struct kvm_vcpu *vcpu, unsigned int exit_nr,
 void kvmppc_core_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
 #ifdef CONFIG_PPC_BOOK3S_64
-        memcpy(to_svcpu(vcpu)->slb, to_book3s(vcpu)->slb_shadow, sizeof(to_svcpu(vcpu)->slb));
+        struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
+        memcpy(svcpu->slb, to_book3s(vcpu)->slb_shadow, sizeof(svcpu->slb));
         memcpy(&get_paca()->shadow_vcpu, to_book3s(vcpu)->shadow_vcpu,
                sizeof(get_paca()->shadow_vcpu));
-        to_svcpu(vcpu)->slb_max = to_book3s(vcpu)->slb_shadow_max;
+        svcpu->slb_max = to_book3s(vcpu)->slb_shadow_max;
+        svcpu_put(svcpu);
 #endif
 
 #ifdef CONFIG_PPC_BOOK3S_32
@@ -70,10 +72,12 @@ void kvmppc_core_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 void kvmppc_core_vcpu_put(struct kvm_vcpu *vcpu)
 {
 #ifdef CONFIG_PPC_BOOK3S_64
-        memcpy(to_book3s(vcpu)->slb_shadow, to_svcpu(vcpu)->slb, sizeof(to_svcpu(vcpu)->slb));
+        struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
+        memcpy(to_book3s(vcpu)->slb_shadow, svcpu->slb, sizeof(svcpu->slb));
         memcpy(to_book3s(vcpu)->shadow_vcpu, &get_paca()->shadow_vcpu,
                sizeof(get_paca()->shadow_vcpu));
-        to_book3s(vcpu)->slb_shadow_max = to_svcpu(vcpu)->slb_max;
+        to_book3s(vcpu)->slb_shadow_max = svcpu->slb_max;
+        svcpu_put(svcpu);
 #endif
 
         kvmppc_giveup_ext(vcpu, MSR_FP);
@@ -308,19 +312,22 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 
         if (page_found == -ENOENT) {
                 /* Page not found in guest PTE entries */
+                struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
                 vcpu->arch.shared->dar = kvmppc_get_fault_dar(vcpu);
-                vcpu->arch.shared->dsisr = to_svcpu(vcpu)->fault_dsisr;
+                vcpu->arch.shared->dsisr = svcpu->fault_dsisr;
                 vcpu->arch.shared->msr |=
-                        (to_svcpu(vcpu)->shadow_srr1 & 0x00000000f8000000ULL);
+                        (svcpu->shadow_srr1 & 0x00000000f8000000ULL);
+                svcpu_put(svcpu);
                 kvmppc_book3s_queue_irqprio(vcpu, vec);
         } else if (page_found == -EPERM) {
                 /* Storage protection */
+                struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
                 vcpu->arch.shared->dar = kvmppc_get_fault_dar(vcpu);
-                vcpu->arch.shared->dsisr =
-                        to_svcpu(vcpu)->fault_dsisr & ~DSISR_NOHPTE;
+                vcpu->arch.shared->dsisr = svcpu->fault_dsisr & ~DSISR_NOHPTE;
                 vcpu->arch.shared->dsisr |= DSISR_PROTFAULT;
                 vcpu->arch.shared->msr |=
-                        (to_svcpu(vcpu)->shadow_srr1 & 0x00000000f8000000ULL);
+                        svcpu->shadow_srr1 & 0x00000000f8000000ULL;
+                svcpu_put(svcpu);
                 kvmppc_book3s_queue_irqprio(vcpu, vec);
         } else if (page_found == -EINVAL) {
                 /* Page not found in guest SLB */
@@ -521,21 +528,25 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
         kvm_resched(vcpu);
         switch (exit_nr) {
         case BOOK3S_INTERRUPT_INST_STORAGE:
+        {
+                struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
+                ulong shadow_srr1 = svcpu->shadow_srr1;
                 vcpu->stat.pf_instruc++;
 
 #ifdef CONFIG_PPC_BOOK3S_32
                 /* We set segments as unused segments when invalidating them. So
                  * treat the respective fault as segment fault. */
-                if (to_svcpu(vcpu)->sr[kvmppc_get_pc(vcpu) >> SID_SHIFT]
-                    == SR_INVALID) {
+                if (svcpu->sr[kvmppc_get_pc(vcpu) >> SID_SHIFT] == SR_INVALID) {
                         kvmppc_mmu_map_segment(vcpu, kvmppc_get_pc(vcpu));
                         r = RESUME_GUEST;
+                        svcpu_put(svcpu);
                         break;
                 }
 #endif
+                svcpu_put(svcpu);
 
                 /* only care about PTEG not found errors, but leave NX alone */
-                if (to_svcpu(vcpu)->shadow_srr1 & 0x40000000) {
+                if (shadow_srr1 & 0x40000000) {
                         r = kvmppc_handle_pagefault(run, vcpu, kvmppc_get_pc(vcpu), exit_nr);
                         vcpu->stat.sp_instruc++;
                 } else if (vcpu->arch.mmu.is_dcbz32(vcpu) &&
@@ -548,33 +559,37 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
                         kvmppc_mmu_pte_flush(vcpu, kvmppc_get_pc(vcpu), ~0xFFFUL);
                         r = RESUME_GUEST;
                 } else {
-                        vcpu->arch.shared->msr |=
-                                to_svcpu(vcpu)->shadow_srr1 & 0x58000000;
+                        vcpu->arch.shared->msr |= shadow_srr1 & 0x58000000;
                         kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
                         r = RESUME_GUEST;
                 }
                 break;
+        }
         case BOOK3S_INTERRUPT_DATA_STORAGE:
         {
                 ulong dar = kvmppc_get_fault_dar(vcpu);
+                struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
+                u32 fault_dsisr = svcpu->fault_dsisr;
                 vcpu->stat.pf_storage++;
 
 #ifdef CONFIG_PPC_BOOK3S_32
                 /* We set segments as unused segments when invalidating them. So
                  * treat the respective fault as segment fault. */
-                if ((to_svcpu(vcpu)->sr[dar >> SID_SHIFT]) == SR_INVALID) {
+                if ((svcpu->sr[dar >> SID_SHIFT]) == SR_INVALID) {
                         kvmppc_mmu_map_segment(vcpu, dar);
                         r = RESUME_GUEST;
+                        svcpu_put(svcpu);
                         break;
                 }
 #endif
+                svcpu_put(svcpu);
 
                 /* The only case we need to handle is missing shadow PTEs */
-                if (to_svcpu(vcpu)->fault_dsisr & DSISR_NOHPTE) {
+                if (fault_dsisr & DSISR_NOHPTE) {
                         r = kvmppc_handle_pagefault(run, vcpu, dar, exit_nr);
                 } else {
                         vcpu->arch.shared->dar = dar;
-                        vcpu->arch.shared->dsisr = to_svcpu(vcpu)->fault_dsisr;
+                        vcpu->arch.shared->dsisr = fault_dsisr;
                         kvmppc_book3s_queue_irqprio(vcpu, exit_nr);
                         r = RESUME_GUEST;
                 }
@@ -610,10 +625,13 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
         case BOOK3S_INTERRUPT_PROGRAM:
         {
                 enum emulation_result er;
+                struct kvmppc_book3s_shadow_vcpu *svcpu;
                 ulong flags;
 
 program_interrupt:
-                flags = to_svcpu(vcpu)->shadow_srr1 & 0x1f0000ull;
+                svcpu = svcpu_get(vcpu);
+                flags = svcpu->shadow_srr1 & 0x1f0000ull;
+                svcpu_put(svcpu);
 
                 if (vcpu->arch.shared->msr & MSR_PR) {
 #ifdef EXIT_DEBUG
@@ -741,14 +759,18 @@ program_interrupt:
                 r = RESUME_GUEST;
                 break;
         default:
+        {
+                struct kvmppc_book3s_shadow_vcpu *svcpu = svcpu_get(vcpu);
+                ulong shadow_srr1 = svcpu->shadow_srr1;
+                svcpu_put(svcpu);
                 /* Ugh - bork here! What did we get? */
                 printk(KERN_EMERG "exit_nr=0x%x | pc=0x%lx | msr=0x%lx\n",
-                        exit_nr, kvmppc_get_pc(vcpu), to_svcpu(vcpu)->shadow_srr1);
+                        exit_nr, kvmppc_get_pc(vcpu), shadow_srr1);
                 r = RESUME_HOST;
                 BUG();
                 break;
         }
-
+        }
 
         if (!(r & RESUME_HOST)) {
                 /* To avoid clobbering exit_reason, only check for signals if