[PATCH] KVM: arm64: Avoid rewinding the PC for trapped SMCs

[PATCH] KVM: arm64: Avoid rewinding the PC for trapped SMCs

[Andrew Scull]

When handling a guest's SError that was identified in __guest_exit, it
is injected back into the guest at the instruction that caused the
switch into hyp. A trapped SMC does not advance the PC so no adjustment
needs to be made to the PC.

Fixes: ddb3d07cfe90 ("arm64: KVM: Inject a Virtual SError if it was pending")
Signed-off-by: Andrew Scull <ascull@google.com>
---
 arch/arm64/kvm/handle_exit.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 98ab33139982..7d9e198ebdf2 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -244,12 +244,11 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
 		u8 esr_ec = ESR_ELx_EC(kvm_vcpu_get_esr(vcpu));
 
 		/*
-		 * HVC/SMC already have an adjusted PC, which we need
+		 * HVC already has an adjusted PC, which we need
 		 * to correct in order to return to after having
 		 * injected the SError.
 		 */
-		if (esr_ec == ESR_ELx_EC_HVC32 || esr_ec == ESR_ELx_EC_HVC64 ||
-		    esr_ec == ESR_ELx_EC_SMC32 || esr_ec == ESR_ELx_EC_SMC64) {
+		if (esr_ec == ESR_ELx_EC_HVC32 || esr_ec == ESR_ELx_EC_HVC64) {
 			u32 adj =  kvm_vcpu_trap_il_is32bit(vcpu) ? 4 : 2;
 			*vcpu_pc(vcpu) -= adj;
 		}
-- 
2.27.0.389.gc38d7665816-goog

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Re: [PATCH] KVM: arm64: Avoid rewinding the PC for trapped SMCs

[James Morse]

Hi Andrew,

On 14/07/2020 10:45, Andrew Scull wrote:
> When handling a guest's SError that was identified in __guest_exit, it
> is injected back into the guest at the instruction that caused the
> switch into hyp. A trapped SMC does not advance the PC so no adjustment
> needs to be made to the PC.

Oops!

Reviewed-by: James Morse <james.morse@arm.com>


Thanks,

James


> Fixes: ddb3d07cfe90 ("arm64: KVM: Inject a Virtual SError if it was pending")
> Signed-off-by: Andrew Scull <ascull@google.com>
> ---
>  arch/arm64/kvm/handle_exit.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 98ab33139982..7d9e198ebdf2 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -244,12 +244,11 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
>  		u8 esr_ec = ESR_ELx_EC(kvm_vcpu_get_esr(vcpu));
>  
>  		/*
> -		 * HVC/SMC already have an adjusted PC, which we need
> +		 * HVC already has an adjusted PC, which we need
>  		 * to correct in order to return to after having
>  		 * injected the SError.
>  		 */
> -		if (esr_ec == ESR_ELx_EC_HVC32 || esr_ec == ESR_ELx_EC_HVC64 ||
> -		    esr_ec == ESR_ELx_EC_SMC32 || esr_ec == ESR_ELx_EC_SMC64) {
> +		if (esr_ec == ESR_ELx_EC_HVC32 || esr_ec == ESR_ELx_EC_HVC64) {
>  			u32 adj =  kvm_vcpu_trap_il_is32bit(vcpu) ? 4 : 2;
>  			*vcpu_pc(vcpu) -= adj;
>  		}
> 

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