On Mon, Aug 03, 2026 at 11:56:49PM +0800, Mark Brown wrote: > In order to allow efficient implementation of GCS implementations are > permitted to do GCS specific caching, with barriers implicit in stack > switch operations and GCSB DSYNC as an explicit barrier. Since we do > not use GCS in the hypervisor or host kernel the hypervisor cannot rely > on any barriers being present in vCPU context switches other than those > it explicitly inserts. Add explicit barriers when loading and saving > vCPU state. >
Reviewed-by: Yuan Yao <[email protected]> > Signed-off-by: Mark Brown <[email protected]> > --- > arch/arm64/kvm/hyp/nvhe/switch.c | 13 +++++++++++++ > arch/arm64/kvm/hyp/vhe/sysreg-sr.c | 14 ++++++++++++++ > 2 files changed, 27 insertions(+) > > diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c > b/arch/arm64/kvm/hyp/nvhe/switch.c > index 7318e3e6a5f3..fe8727bf2833 100644 > --- a/arch/arm64/kvm/hyp/nvhe/switch.c > +++ b/arch/arm64/kvm/hyp/nvhe/switch.c > @@ -301,6 +301,12 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu) > */ > dsb(nsh); > > + /* > + * Ensure any GCS memory effects are visible to this CPU. > + */ > + if (ctxt_has_gcs(guest_ctxt)) > + gcsb_dsync(); > + > __kvm_adjust_pc(vcpu); > > /* > @@ -345,6 +351,13 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu) > */ > dsb(nsh); > > + /* > + * Ensure any GCS memory effects from the outgoing vCPU are > + * visible elsewhere. > + */ > + if (ctxt_has_gcs(guest_ctxt)) > + gcsb_dsync(); > + > __deactivate_traps(vcpu); > __load_host_stage2(); > > diff --git a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c > b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c > index 2431c18f5792..4594992b008c 100644 > --- a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c > +++ b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c > @@ -239,6 +239,13 @@ void __vcpu_load_switch_sysregs(struct kvm_vcpu *vcpu) > if (vcpu_has_nv(vcpu)) > dsb(nsh); > > + /* > + * Ensure any GCS memory effects are visible to the incoming > + * vCPU. > + */ > + if (ctxt_has_gcs(guest_ctxt)) > + gcsb_dsync(); > + > /* > * Load guest EL1 and user state > * > @@ -299,5 +306,12 @@ void __vcpu_put_switch_sysregs(struct kvm_vcpu *vcpu) > /* Restore host user state */ > __sysreg_restore_user_state(host_ctxt); > > + /* > + * Ensure any GCS memory effects from the outgoing vCPU are > + * visible elsewhere. > + */ > + if (ctxt_has_gcs(guest_ctxt)) > + gcsb_dsync(); > + > vcpu_clear_flag(vcpu, SYSREGS_ON_CPU); > } > > -- > 2.47.3 >
