From: Fuad Tabba Date: Fri, 13 Feb 2026 14:38:12 +0000 (+0000) Subject: KVM: arm64: Hide S1POE from guests when not supported by the host X-Git-Tag: v7.0-rc2~1^2^2~8 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f66857bafd4f151c5cc6856e47be2e12c1721e43;p=thirdparty%2Fkernel%2Flinux.git 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: 70ed7238297f ("KVM: arm64: Sanitise ID_AA64MMFR3_EL1") Signed-off-by: Fuad Tabba Link: https://patch.msgid.link/20260213143815.1732675-2-tabba@google.com Signed-off-by: Marc Zyngier --- diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index a7cd0badc20cc..1b4cacb6e918a 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -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;