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KVM: PPC: Call SLB patching code in interrupt safe manner

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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>
This commit is contained in:
Alexander Graf 2010-01-08 02:58:06 +01:00 committed by Marcelo Tosatti
parent bc90923e27
commit 021ec9c69f
9 changed files with 34 additions and 21 deletions
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1
arch/powerpc/include/asm/kvm_book3s.h
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@ -121,6 +121,7 @@ extern void kvmppc_set_bat(struct kvm_vcpu *vcpu, struct kvmppc_bat *bat,
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)
{

1
arch/powerpc/include/asm/kvm_book3s_64_asm.h
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@ -69,7 +69,6 @@ struct kvmppc_book3s_shadow_vcpu {
ulong scratch0;
ulong scratch1;
ulong vmhandler;
ulong rmhandler;
};
#endif /*__ASSEMBLY__ */

1
arch/powerpc/include/asm/kvm_host.h
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@ -167,6 +167,7 @@ struct kvm_vcpu_arch {
ulong trampoline_lowmem;
ulong trampoline_enter;
ulong highmem_handler;
ulong rmcall;
ulong host_paca_phys;
struct kvmppc_mmu mmu;
#endif

3
arch/powerpc/kernel/asm-offsets.c
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@ -214,8 +214,6 @@ int main(void)
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 @@ int main(void)
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));

1
arch/powerpc/kvm/book3s.c
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@ -919,6 +919,7 @@ struct kvm_vcpu *kvmppc_core_vcpu_create(struct kvm *kvm, unsigned int id)
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;

1
arch/powerpc/kvm/book3s_64_exports.c
View File

@ -22,3 +22,4 @@
EXPORT_SYMBOL_GPL(kvmppc_trampoline_enter);
EXPORT_SYMBOL_GPL(kvmppc_trampoline_lowmem);
EXPORT_SYMBOL_GPL(kvmppc_rmcall);

25
arch/powerpc/kvm/book3s_64_interrupts.S
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@ -95,17 +95,14 @@ kvm_start_entry:
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 @@ kvm_start_lightweight:
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

18
arch/powerpc/kvm/book3s_64_rmhandlers.S
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@ -140,6 +140,24 @@ kvmppc_handler_lowmem_trampoline:
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

4
arch/powerpc/kvm/book3s_64_slb.S
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@ -63,6 +63,10 @@ kvmppc_handler_trampoline_enter:
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