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KVM: arm64: Force ID_AA64PFR0_EL1.GIC=1 when exposing a virtual GICv3
authorMarc Zyngier <maz@kernel.org>
Sun, 10 Oct 2021 15:09:06 +0000 (16:09 +0100)
committerMarc Zyngier <maz@kernel.org>
Sun, 17 Oct 2021 10:06:36 +0000 (11:06 +0100)
commit562e530fd7707aad7fed953692d1835612238966
treec5c826ecc1cd23f3a57467f128c5e91caa3aa393
parent9e1ff307c779ce1f0f810c7ecce3d95bbae40896
KVM: arm64: Force ID_AA64PFR0_EL1.GIC=1 when exposing a virtual GICv3

Until now, we always let ID_AA64PFR0_EL1.GIC reflect the value
visible on the host, even if we were running a GICv2-enabled VM
on a GICv3+compat host.

That's fine, but we also now have the case of a host that does not
expose ID_AA64PFR0_EL1.GIC==1 despite having a vGIC. Yes, this is
confusing. Thank you M1.

Let's go back to first principles and expose ID_AA64PFR0_EL1.GIC=1
when a GICv3 is exposed to the guest. This also hides a GICv4.1
CPU interface from the guest which has no business knowing about
the v4.1 extension.

Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211010150910.2911495-2-maz@kernel.org
arch/arm64/kvm/sys_regs.c