On Wed, Aug 12, 2026 at 08:12:02PM +0100, Mark Brown wrote:
> GCS introduces a number of system registers, on systems with GCS we need
> to context switch them and expose them to VMMs to allow guests to use
> GCS.
>
> In order to allow guests to use GCS we also need to configure
> HCRX_EL2.GCSEn, if this is not set GCS instructions will be noops and
> CHKFEAT will report GCS as disabled.
>
> Signed-off-by: Mark Brown <[email protected]>
> ---
> arch/arm64/include/asm/kvm_emulate.h | 3 +++
> arch/arm64/include/asm/kvm_host.h | 14 ++++++++++
> arch/arm64/include/asm/vncr_mapping.h | 2 ++
> arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 31 ++++++++++++++++++++++
> arch/arm64/kvm/hyp/vhe/sysreg-sr.c | 10 +++++++
> arch/arm64/kvm/sys_regs.c | 42
> ++++++++++++++++++++++++++++++
> 6 files changed, 102 insertions(+)
>
[...]
> diff --git a/arch/arm64/include/asm/kvm_host.h
> b/arch/arm64/include/asm/kvm_host.h
> index bae2c4f92ef5..1f0da8988961 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
[...]
> @@ -1648,6 +1658,10 @@ void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64
> val);
> #define kvm_has_sctlr2(k) \
> (kvm_has_feat((k), ID_AA64MMFR3_EL1, SCTLRX, IMP))
>
> +#define kvm_has_gcs(k) \
> + (system_supports_gcs() && \
> + kvm_has_feat((k), ID_AA64PFR1_EL1, GCS, IMP))
> +
> static inline bool kvm_arch_has_irq_bypass(void)
> {
> return true;
[...]
> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> index a17cbe7582de..053d7b3c5104 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h
[...]
> @@ -131,6 +137,17 @@ static inline bool ctxt_has_sctlr2(struct
> kvm_cpu_context *ctxt)
> return kvm_has_sctlr2(kern_hyp_va(vcpu->kvm));
> }
>
> +static inline bool ctxt_has_gcs(struct kvm_cpu_context *ctxt)
> +{
> + struct kvm_vcpu *vcpu;
> +
> + if (!cpus_have_final_cap(ARM64_HAS_GCS))
> + return false;
> +
> + vcpu = ctxt_to_vcpu(ctxt);
> + return kvm_has_feat(kern_hyp_va(vcpu->kvm), ID_AA64PFR1_EL1, GCS, IMP);
> +}
This seems to duplicate some work done in kvm_has_gcs(), can we use
kvm_has_gcs() in this function?
static inline bool ctxt_has_gcs(struct kvm_cpu_context *ctxt)
{
struct kvm_vcpu *vcpu = ctxt_to_vcpu(ctxt);
return kvm_has_gcs(kern_hyp_va(vcpu->kvm));
}
Thanks,
Wei-Lin Chang
[...]
