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Subject[RFC 13/55] KVM: arm64: Handle eret instruction traps
Date
When HCR.NV bit is set, eret instruction execution in the guest
hypervisor will trap with EC code 0x1A. Let ELR_EL2 and SPSR_EL2 state
from the guest's perspective be restored to the hardware on the next
guest entry.

Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
---
arch/arm64/include/asm/esr.h | 1 +
arch/arm64/kvm/handle_exit.c | 12 ++++++++++++
arch/arm64/kvm/trace.h | 21 +++++++++++++++++++++
3 files changed, 34 insertions(+)

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index d14c478..f32e3a7 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -42,6 +42,7 @@
#define ESR_ELx_EC_HVC64 (0x16)
#define ESR_ELx_EC_SMC64 (0x17)
#define ESR_ELx_EC_SYS64 (0x18)
+#define ESR_ELx_EC_ERET (0x1A)
/* Unallocated EC: 0x19 - 0x1E */
#define ESR_ELx_EC_IMP_DEF (0x1f)
#define ESR_ELx_EC_IABT_LOW (0x20)
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index a204adf..4e4a915 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -125,6 +125,17 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
return ret;
}

+static int kvm_handle_eret(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+ trace_kvm_nested_eret(vcpu, vcpu_el2_reg(vcpu, ELR_EL2),
+ vcpu_el2_reg(vcpu, SPSR_EL2));
+
+ *vcpu_pc(vcpu) = vcpu_el2_reg(vcpu, ELR_EL2);
+ *vcpu_cpsr(vcpu) = vcpu_el2_reg(vcpu, SPSR_EL2);
+
+ return 1;
+}
+
static exit_handle_fn arm_exit_handlers[] = {
[ESR_ELx_EC_WFx] = kvm_handle_wfx,
[ESR_ELx_EC_CP15_32] = kvm_handle_cp15_32,
@@ -137,6 +148,7 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
[ESR_ELx_EC_HVC64] = handle_hvc,
[ESR_ELx_EC_SMC64] = handle_smc,
[ESR_ELx_EC_SYS64] = kvm_handle_sys_reg,
+ [ESR_ELx_EC_ERET] = kvm_handle_eret,
[ESR_ELx_EC_IABT_LOW] = kvm_handle_guest_abort,
[ESR_ELx_EC_DABT_LOW] = kvm_handle_guest_abort,
[ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug,
diff --git a/arch/arm64/kvm/trace.h b/arch/arm64/kvm/trace.h
index 7c86cfb..5f40987 100644
--- a/arch/arm64/kvm/trace.h
+++ b/arch/arm64/kvm/trace.h
@@ -187,6 +187,27 @@
TP_printk("vcpu: %p, inject exception to vEL2: ESR_EL2 0x%lx, vector: 0x%016lx",
__entry->vcpu, __entry->esr_el2, __entry->pc)
);
+
+TRACE_EVENT(kvm_nested_eret,
+ TP_PROTO(struct kvm_vcpu *vcpu, unsigned long elr_el2,
+ unsigned long spsr_el2),
+ TP_ARGS(vcpu, elr_el2, spsr_el2),
+
+ TP_STRUCT__entry(
+ __field(struct kvm_vcpu *, vcpu)
+ __field(unsigned long, elr_el2)
+ __field(unsigned long, spsr_el2)
+ ),
+
+ TP_fast_assign(
+ __entry->vcpu = vcpu;
+ __entry->elr_el2 = elr_el2;
+ __entry->spsr_el2 = spsr_el2;
+ ),
+
+ TP_printk("vcpu: %p, eret to elr_el2: 0x%016lx, with spsr_el2: 0x%08lx",
+ __entry->vcpu, __entry->elr_el2, __entry->spsr_el2)
+);
#endif /* _TRACE_ARM64_KVM_H */

#undef TRACE_INCLUDE_PATH
--
1.9.1

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