Commit f66857ba authored by Fuad Tabba's avatar Fuad Tabba Committed by Marc Zyngier
Browse files

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



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: 70ed7238 ("KVM: arm64: Sanitise ID_AA64MMFR3_EL1")
Signed-off-by: default avatarFuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260213143815.1732675-2-tabba@google.com


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 63163661

arch/arm64/kvm/sys_regs.c

+3 −0
Original line number Diff line number Diff line
@@ -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;