From: Marc Zyngier maz@kernel.org
commit 0370964dd3ff7d3d406f292cb443a927952cbd05 upstream.
On a VHE system, the EL1 state is left in the CPU most of the time, and only syncronized back to memory when vcpu_put() is called (most of the time on preemption).
Which means that when injecting an exception, we'd better have a way to either: (1) write directly to the EL1 sysregs (2) synchronize the state back to memory, and do the changes there
For an AArch64, we already do (1), so we are safe. Unfortunately, doing the same thing for AArch32 would be pretty invasive. Instead, we can easily implement (2) by calling the put/load architectural backends, and keep preemption disabled. We can then reload the state back into EL1.
Cc: stable@vger.kernel.org Reported-by: James Morse james.morse@arm.com Signed-off-by: Marc Zyngier maz@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm/include/asm/kvm_host.h | 2 ++ arch/arm64/include/asm/kvm_host.h | 2 ++ virt/kvm/arm/aarch32.c | 28 ++++++++++++++++++++++++++++ 3 files changed, 32 insertions(+)
--- a/arch/arm/include/asm/kvm_host.h +++ b/arch/arm/include/asm/kvm_host.h @@ -364,4 +364,6 @@ static inline void kvm_vcpu_put_sysregs( struct kvm *kvm_arch_alloc_vm(void); void kvm_arch_free_vm(struct kvm *kvm);
+#define kvm_arm_vcpu_loaded(vcpu) (false) + #endif /* __ARM_KVM_HOST_H__ */ --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -537,4 +537,6 @@ void kvm_vcpu_put_sysregs(struct kvm_vcp struct kvm *kvm_arch_alloc_vm(void); void kvm_arch_free_vm(struct kvm *kvm);
+#define kvm_arm_vcpu_loaded(vcpu) ((vcpu)->arch.sysregs_loaded_on_cpu) + #endif /* __ARM64_KVM_HOST_H__ */ --- a/virt/kvm/arm/aarch32.c +++ b/virt/kvm/arm/aarch32.c @@ -44,6 +44,26 @@ static const u8 return_offsets[8][2] = { [7] = { 4, 4 }, /* FIQ, unused */ };
+static bool pre_fault_synchronize(struct kvm_vcpu *vcpu) +{ + preempt_disable(); + if (kvm_arm_vcpu_loaded(vcpu)) { + kvm_arch_vcpu_put(vcpu); + return true; + } + + preempt_enable(); + return false; +} + +static void post_fault_synchronize(struct kvm_vcpu *vcpu, bool loaded) +{ + if (loaded) { + kvm_arch_vcpu_load(vcpu, smp_processor_id()); + preempt_enable(); + } +} + /* * When an exception is taken, most CPSR fields are left unchanged in the * handler. However, some are explicitly overridden (e.g. M[4:0]). @@ -166,7 +186,10 @@ static void prepare_fault32(struct kvm_v
void kvm_inject_undef32(struct kvm_vcpu *vcpu) { + bool loaded = pre_fault_synchronize(vcpu); + prepare_fault32(vcpu, PSR_AA32_MODE_UND, 4); + post_fault_synchronize(vcpu, loaded); }
/* @@ -179,6 +202,9 @@ static void inject_abt32(struct kvm_vcpu u32 vect_offset; u32 *far, *fsr; bool is_lpae; + bool loaded; + + loaded = pre_fault_synchronize(vcpu);
if (is_pabt) { vect_offset = 12; @@ -202,6 +228,8 @@ static void inject_abt32(struct kvm_vcpu /* no need to shuffle FS[4] into DFSR[10] as its 0 */ *fsr = DFSR_FSC_EXTABT_nLPAE; } + + post_fault_synchronize(vcpu, loaded); }
void kvm_inject_dabt32(struct kvm_vcpu *vcpu, unsigned long addr)