Re: [PATCH v18 03/14] KVM: arm64: Manage GCS access and registers for guests

Mark Brown <[email protected]> Wed, 5 Aug 2026 13:32:26 +0100

Newsgroups	dev.linux.lists.kvmarm,org.infradead.lists.linux-arm-kernel,org.kernel.vger.linux-doc,org.kernel.vger.linux-kernel,org.kernel.vger.linux-kselftest
Message-ID	<[email protected]>

On Wed, Aug 05, 2026 at 05:48:04PM +0800, Yao Yuan wrote:
> On Mon, Aug 03, 2026 at 11:56:48PM +0800, Mark Brown wrote:

> >
> >  		if (ctxt_has_s1poe(&vcpu->arch.ctxt))
> >  			write_sysreg_el1(__vcpu_sys_reg(vcpu, POR_EL2), SYS_POR);
> > +
> > +		if (ctxt_has_gcs(&vcpu->arch.ctxt)) {
> > +			write_sysreg_el1(__vcpu_sys_reg(vcpu, GCSCR_EL2), SYS_GCSCR);
> > +			write_sysreg_el1(__vcpu_sys_reg(vcpu, GCSPR_EL2), SYS_GCSPR);
> > +		}

> Looks the s1pie checking for GCS vEL2 context switch is
> necessary yet IIUC, KVM does vEL2 context switch for nested
> L1's EL2, it should follow same rule as non-nested L1's EL1
> context switch.

Right, it's not really needed in either case but hopefully helps code
generation a bit.  Thanks for spotting that.

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