KVM: PPC: Call SLB patching code in interrupt safe manner
Currently we're racy when doing the transition from IR=1 to IR=0, from
the module memory entry code to the real mode SLB switching code.
To work around that I took a look at the RTAS entry code which is faced
with a similar problem and did the same thing:
A small helper in linear mapped memory that does mtmsr with IR=0 and
then RFIs info the actual handler.
Thanks to that trick we can safely take page faults in the entry code
and only need to be really wary of what to do as of the SLB switching
part.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index f192017..c91be0f 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -121,6 +121,7 @@
extern u32 kvmppc_trampoline_lowmem;
extern u32 kvmppc_trampoline_enter;
+extern void kvmppc_rmcall(ulong srr0, ulong srr1);
static inline struct kvmppc_vcpu_book3s *to_book3s(struct kvm_vcpu *vcpu)
{
diff --git a/arch/powerpc/include/asm/kvm_book3s_64_asm.h b/arch/powerpc/include/asm/kvm_book3s_64_asm.h
index fca9404..183461b 100644
--- a/arch/powerpc/include/asm/kvm_book3s_64_asm.h
+++ b/arch/powerpc/include/asm/kvm_book3s_64_asm.h
@@ -69,7 +69,6 @@
ulong scratch0;
ulong scratch1;
ulong vmhandler;
- ulong rmhandler;
};
#endif /*__ASSEMBLY__ */
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index d615fa8..f7215e6 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -167,6 +167,7 @@
ulong trampoline_lowmem;
ulong trampoline_enter;
ulong highmem_handler;
+ ulong rmcall;
ulong host_paca_phys;
struct kvmppc_mmu mmu;
#endif
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 1501e77..ee99354 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -214,8 +214,6 @@
DEFINE(PACA_KVM_HOST_R2, offsetof(struct paca_struct, shadow_vcpu.host_r2));
DEFINE(PACA_KVM_VMHANDLER, offsetof(struct paca_struct,
shadow_vcpu.vmhandler));
- DEFINE(PACA_KVM_RMHANDLER, offsetof(struct paca_struct,
- shadow_vcpu.rmhandler));
DEFINE(PACA_KVM_SCRATCH0, offsetof(struct paca_struct,
shadow_vcpu.scratch0));
DEFINE(PACA_KVM_SCRATCH1, offsetof(struct paca_struct,
@@ -438,6 +436,7 @@
DEFINE(VCPU_TRAMPOLINE_LOWMEM, offsetof(struct kvm_vcpu, arch.trampoline_lowmem));
DEFINE(VCPU_TRAMPOLINE_ENTER, offsetof(struct kvm_vcpu, arch.trampoline_enter));
DEFINE(VCPU_HIGHMEM_HANDLER, offsetof(struct kvm_vcpu, arch.highmem_handler));
+ DEFINE(VCPU_RMCALL, offsetof(struct kvm_vcpu, arch.rmcall));
DEFINE(VCPU_HFLAGS, offsetof(struct kvm_vcpu, arch.hflags));
#else
DEFINE(VCPU_CR, offsetof(struct kvm_vcpu, arch.cr));
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index 3e06eae..1317392 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -919,6 +919,7 @@
vcpu->arch.trampoline_lowmem = kvmppc_trampoline_lowmem;
vcpu->arch.trampoline_enter = kvmppc_trampoline_enter;
vcpu->arch.highmem_handler = (ulong)kvmppc_handler_highmem;
+ vcpu->arch.rmcall = *(ulong*)kvmppc_rmcall;
vcpu->arch.shadow_msr = MSR_USER64;
diff --git a/arch/powerpc/kvm/book3s_64_exports.c b/arch/powerpc/kvm/book3s_64_exports.c
index 5b2db38..99b0712 100644
--- a/arch/powerpc/kvm/book3s_64_exports.c
+++ b/arch/powerpc/kvm/book3s_64_exports.c
@@ -22,3 +22,4 @@
EXPORT_SYMBOL_GPL(kvmppc_trampoline_enter);
EXPORT_SYMBOL_GPL(kvmppc_trampoline_lowmem);
+EXPORT_SYMBOL_GPL(kvmppc_rmcall);
diff --git a/arch/powerpc/kvm/book3s_64_interrupts.S b/arch/powerpc/kvm/book3s_64_interrupts.S
index 3c0ba55..33aef53 100644
--- a/arch/powerpc/kvm/book3s_64_interrupts.S
+++ b/arch/powerpc/kvm/book3s_64_interrupts.S
@@ -95,17 +95,14 @@
ld r3, VCPU_HIGHMEM_HANDLER(r4)
std r3, PACA_KVM_VMHANDLER(r13)
- ld r3, VCPU_TRAMPOLINE_ENTER(r4)
- std r3, PACA_KVM_RMHANDLER(r13)
-
kvm_start_lightweight:
ld r9, VCPU_PC(r4) /* r9 = vcpu->arch.pc */
ld r10, VCPU_SHADOW_MSR(r4) /* r10 = vcpu->arch.shadow_msr */
/* Load some guest state in the respective registers */
- ld r3, VCPU_CTR(r4) /* r3 = vcpu->arch.ctr */
- mtctr r3 /* CTR = r3 */
+ ld r5, VCPU_CTR(r4) /* r5 = vcpu->arch.ctr */
+ /* will be swapped in by rmcall */
ld r3, VCPU_LR(r4) /* r3 = vcpu->arch.lr */
mtlr r3 /* LR = r3 */
@@ -131,22 +128,14 @@
no_dcbz32_on:
- /* This sets the Magic value for the trampoline */
+ ld r6, VCPU_RMCALL(r4)
+ mtctr r6
- /* XXX this needs to move into a safe function, so we can
- be sure we don't get any interrupts */
-
- li r11, 1
- stb r11, PACA_KVM_IN_GUEST(r13)
-
- ld r3, PACA_KVM_RMHANDLER(r13)
- mtsrr0 r3
-
- LOAD_REG_IMMEDIATE(r3, MSR_KERNEL & ~(MSR_IR | MSR_DR))
- mtsrr1 r3
+ ld r3, VCPU_TRAMPOLINE_ENTER(r4)
+ LOAD_REG_IMMEDIATE(r4, MSR_KERNEL & ~(MSR_IR | MSR_DR))
/* Jump to SLB patching handlder and into our guest */
- RFI
+ bctr
/*
* This is the handler in module memory. It gets jumped at from the
diff --git a/arch/powerpc/kvm/book3s_64_rmhandlers.S b/arch/powerpc/kvm/book3s_64_rmhandlers.S
index 9ad1c26..e7091c9 100644
--- a/arch/powerpc/kvm/book3s_64_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_64_rmhandlers.S
@@ -140,6 +140,24 @@
blr
kvmppc_handler_lowmem_trampoline_end:
+/*
+ * Call a function in real mode
+ *
+ * Input Registers:
+ *
+ * R3 = function
+ * R4 = MSR
+ * R5 = CTR
+ *
+ */
+_GLOBAL(kvmppc_rmcall)
+ mtmsr r4 /* Disable relocation, so mtsrr
+ doesn't get interrupted */
+ mtctr r5
+ mtsrr0 r3
+ mtsrr1 r4
+ RFI
+
.global kvmppc_trampoline_lowmem
kvmppc_trampoline_lowmem:
.long kvmppc_handler_lowmem_trampoline - _stext
diff --git a/arch/powerpc/kvm/book3s_64_slb.S b/arch/powerpc/kvm/book3s_64_slb.S
index d07b886..35b76272 100644
--- a/arch/powerpc/kvm/book3s_64_slb.S
+++ b/arch/powerpc/kvm/book3s_64_slb.S
@@ -63,6 +63,10 @@
mtsrr0 r9
mtsrr1 r10
+ /* Activate guest mode, so faults get handled by KVM */
+ li r11, KVM_GUEST_MODE_GUEST
+ stb r11, PACA_KVM_IN_GUEST(r13)
+
/* Remove LPAR shadow entries */
#if SLB_NUM_BOLTED == 3