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KVM: arm64: Hide S1POE from guests when not supported by the host

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When CONFIG_ARM64_POE is disabled, KVM does not save/restore POR_EL1.
However, ID_AA64MMFR3_EL1 sanitisation currently exposes the feature to
guests whenever the hardware supports it, ignoring the host kernel
configuration.

If a guest detects this feature and attempts to use it, the host will
fail to context-switch POR_EL1, potentially leading to state corruption.

Fix this by masking ID_AA64MMFR3_EL1.S1POE in the sanitised system
registers, preventing KVM from advertising the feature when the host
does not support it (i.e. system_supports_poe() is false).

Fixes: 70ed723829 ("KVM: arm64: Sanitise ID_AA64MMFR3_EL1")
Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260213143815.1732675-2-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Fuad Tabba 2026-02-13 14:38:12 +00:00 • committed by Marc Zyngier
parent 6316366129
commit f66857bafd
1 changed files with 3 additions and 0 deletions
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3
arch/arm64/kvm/sys_regs.c
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@ -1816,6 +1816,9 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu,
ID_AA64MMFR3_EL1_SCTLRX |
ID_AA64MMFR3_EL1_S1POE |
ID_AA64MMFR3_EL1_S1PIE;
if (!system_supports_poe())
val &= ~ID_AA64MMFR3_EL1_S1POE;
break;
case SYS_ID_MMFR4_EL1:
val &= ~ID_MMFR4_EL1_CCIDX;