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/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