From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 675A03EA5BE; Sat, 28 Feb 2026 17:41:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300518; cv=none; b=HrpUNNazjg1g6gehOhxiioCmLC7/J4fvWImUcU5ZLAz/2Cp+bTqgkTdTyuqN8QjKdHNEL1B1c3LSm9l2ri7hCl2+YodXacFoc5OGUzRbC4AdNGlqJvj9qD/N89ijIqyW1UwexOAWtXXamde+xz3ny7Ec/qRhTFdIOUzo/jHSiVc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300518; c=relaxed/simple; bh=eEEVN9oLK40Dq0Ox1VO1dkFABqXhehEfPgc1pr5Ax4w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YIoo42mtHhMCWXp3QP9/XKrYoXKALSWsqXSWxavfaHKRvbV8+lIvODRDTe5gB/9tiaNGZNhxFlhO2xSEAhq5u58CT3GGQrDdDwCKVvFjD9N15y2XE05oK8GmSIECPqhS2XSU6RszqlZv+vzwSgfbFS0U+YU7tuloJWPgWNolhHw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=skV72/zd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="skV72/zd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96C6FC19423; Sat, 28 Feb 2026 17:41:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772300518; bh=eEEVN9oLK40Dq0Ox1VO1dkFABqXhehEfPgc1pr5Ax4w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=skV72/zdAqq3SVUpQ9514HCBhO3/QNgDrLwmevvmYDrBkFhV2A6W0kElMkxXHDKxA A+pMboAA+lr5ddE/2EYF4UkYg9jvCJG8YoJPOi10IF3Ytogv/PR0RJkaS4Mha4Qy7m Xa4S/080ZrTnL9FxePDXMt3SheEruT3Pc8PL/du67qESON1ohm0QOgKGUonkam1U63 dDXEIeWSu2z5MWjJko2fUkdSIlU2RlzacuuF7TOTqIEo4MwGFb8WRdn33egKtVz36v 0hWrFwKcTqC7YuFaol+gF6PgH1XQG16C7JsJQNv2dAw1kfGfiXEOizLkvHrLwTLAnf cspHAP/ujPweQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sean Christopherson , Jim Mattson , Sasha Levin Subject: [PATCH 6.19 556/844] KVM: x86: Return "unsupported" instead of "invalid" on access to unsupported PV MSR Date: Sat, 28 Feb 2026 12:27:49 -0500 Message-ID: <20260228173244.1509663-557-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228173244.1509663-1-sashal@kernel.org> References: <20260228173244.1509663-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Sean Christopherson [ Upstream commit 5bb9ac1865123356337a389af935d3913ee917ed ] Return KVM_MSR_RET_UNSUPPORTED instead of '1' (which for all intents and purposes means "invalid") when rejecting accesses to KVM PV MSRs to adhere to KVM's ABI of allowing host reads and writes of '0' to MSRs that are advertised to userspace via KVM_GET_MSR_INDEX_LIST, even if the vCPU model doesn't support the MSR. E.g. running a QEMU VM with -cpu host,-kvmclock,kvm-pv-enforce-cpuid yields: qemu: error: failed to set MSR 0x12 to 0x0 qemu: target/i386/kvm/kvm.c:3301: kvm_buf_set_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed. Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID") Cc: stable@vger.kernel.org Reviewed-by: Jim Mattson Link: https://patch.msgid.link/20251230205948.4094097-1-seanjc@google.com Signed-off-by: Sean Christopherson Signed-off-by: Sasha Levin --- arch/x86/kvm/x86.c | 40 ++++++++++++++++++++-------------------- 1 file changed, 20 insertions(+), 20 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 72d37c8930ad7..042ebda1a6576 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4096,47 +4096,47 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_KVM_WALL_CLOCK_NEW: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE2)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; vcpu->kvm->arch.wall_clock = data; kvm_write_wall_clock(vcpu->kvm, data, 0); break; case MSR_KVM_WALL_CLOCK: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; vcpu->kvm->arch.wall_clock = data; kvm_write_wall_clock(vcpu->kvm, data, 0); break; case MSR_KVM_SYSTEM_TIME_NEW: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE2)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; kvm_write_system_time(vcpu, data, false, msr_info->host_initiated); break; case MSR_KVM_SYSTEM_TIME: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; kvm_write_system_time(vcpu, data, true, msr_info->host_initiated); break; case MSR_KVM_ASYNC_PF_EN: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; if (kvm_pv_enable_async_pf(vcpu, data)) return 1; break; case MSR_KVM_ASYNC_PF_INT: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; if (kvm_pv_enable_async_pf_int(vcpu, data)) return 1; break; case MSR_KVM_ASYNC_PF_ACK: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; if (data & 0x1) { /* * Pairs with the smp_mb__after_atomic() in @@ -4149,7 +4149,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_KVM_STEAL_TIME: if (!guest_pv_has(vcpu, KVM_FEATURE_STEAL_TIME)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; if (unlikely(!sched_info_on())) return 1; @@ -4167,7 +4167,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_KVM_PV_EOI_EN: if (!guest_pv_has(vcpu, KVM_FEATURE_PV_EOI)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; if (kvm_lapic_set_pv_eoi(vcpu, data, sizeof(u8))) return 1; @@ -4175,7 +4175,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_KVM_POLL_CONTROL: if (!guest_pv_has(vcpu, KVM_FEATURE_POLL_CONTROL)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; /* only enable bit supported */ if (data & (-1ULL << 1)) @@ -4476,61 +4476,61 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_KVM_WALL_CLOCK: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->kvm->arch.wall_clock; break; case MSR_KVM_WALL_CLOCK_NEW: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE2)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->kvm->arch.wall_clock; break; case MSR_KVM_SYSTEM_TIME: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.time; break; case MSR_KVM_SYSTEM_TIME_NEW: if (!guest_pv_has(vcpu, KVM_FEATURE_CLOCKSOURCE2)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.time; break; case MSR_KVM_ASYNC_PF_EN: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.apf.msr_en_val; break; case MSR_KVM_ASYNC_PF_INT: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.apf.msr_int_val; break; case MSR_KVM_ASYNC_PF_ACK: if (!guest_pv_has(vcpu, KVM_FEATURE_ASYNC_PF_INT)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = 0; break; case MSR_KVM_STEAL_TIME: if (!guest_pv_has(vcpu, KVM_FEATURE_STEAL_TIME)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.st.msr_val; break; case MSR_KVM_PV_EOI_EN: if (!guest_pv_has(vcpu, KVM_FEATURE_PV_EOI)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.pv_eoi.msr_val; break; case MSR_KVM_POLL_CONTROL: if (!guest_pv_has(vcpu, KVM_FEATURE_POLL_CONTROL)) - return 1; + return KVM_MSR_RET_UNSUPPORTED; msr_info->data = vcpu->arch.msr_kvm_poll_control; break; -- 2.51.0