Re: [PATCH v3 04/15] KVM: arm64: nv: Drop VCPU_HYP_CONTEXT flag

Oliver Upton
2024-04-16T20:06:33Z

On Thu, Mar 21, 2024 at 03:53:45PM +0000, Marc Zyngier wrote:
> It has become obvious that HCR_EL2.NV serves the exact same use
> as VCPU_HYP_CONTEXT, only in an architectural way. So just drop
> the flag for good.
>
> Reviewed-by: Joey Gouly <joey.gouly@arm.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
> arch/arm64/include/asm/kvm_host.h | 2 --
> arch/arm64/kvm/hyp/vhe/switch.c | 7 +------
> 2 files changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 839c76529bb2..3f1c3c91e5c2 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -816,8 +816,6 @@ struct kvm_vcpu_arch {
> #define DEBUG_STATE_SAVE_SPE __vcpu_single_flag(iflags, BIT(5))
> /* Save TRBE context if active */
> #define DEBUG_STATE_SAVE_TRBE __vcpu_single_flag(iflags, BIT(6))
> -/* vcpu running in HYP context */
> -#define VCPU_HYP_CONTEXT __vcpu_single_flag(iflags, BIT(7))
>
> /* SVE enabled for host EL0 */
> #define HOST_SVE_ENABLED __vcpu_single_flag(sflags, BIT(0))
> diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
> index 1581df6aec87..58415783fd53 100644
> --- a/arch/arm64/kvm/hyp/vhe/switch.c
> +++ b/arch/arm64/kvm/hyp/vhe/switch.c
> @@ -197,7 +197,7 @@ static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code)
> * If we were in HYP context on entry, adjust the PSTATE view
> * so that the usual helpers work correctly.
> */
> - if (unlikely(vcpu_get_flag(vcpu, VCPU_HYP_CONTEXT))) {
> + if (unlikely(read_sysreg(hcr_el2) & HCR_NV)) {

Can this be additionally predicated on vcpu_has_nv() so we condition on
the NV cpucap and avoid the sysreg read on non-nesting hardware?

--
Thanks,
Oliver