From nobody Tue Dec 2 02:42:57 2025 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6CF4F30E0E4 for ; Tue, 18 Nov 2025 22:23:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763504616; cv=none; b=BrO/+rsXnXoQgFvBH420i60agr5p/auKayhgY5ODNcA7ryVN8azmdHZOvPNbUdMGWzuXo7s/SGSK9jTCMDIbR43qwzd3KXOAP0iR/1wU5zDAy76GivIuFt79u04a66Xb7GRHKthLmNglExpF4kLEuGO9HqzBKEmAnyJBCRGxLJ8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763504616; c=relaxed/simple; bh=/o8KfZ3cNcE/BiIE20gNBxFK6IuWDrd7yhoJMvADFS8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=fVARzAbKqc2EzYGNiZd2d3S2g3IuEnlcksFvi/zOJoHKEwGqM/0y/U0HVVBj/jQ4R8e5GeJUyV7qxJ+a8ucz4icrH6+0BVRcLQ0GB6+EpYVrMUMssKlYJWvZXil0PMY9S2LsQuvlhU8u1dclS1I1YgBiubRQzd38QjiUvcL0Cxg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=rr4QUzhR; arc=none smtp.client-ip=209.85.214.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="rr4QUzhR" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-29809acd049so105025465ad.3 for ; Tue, 18 Nov 2025 14:23:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1763504615; x=1764109415; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=QKvebzST2buQwrtL7F9ca9a+LG6gPYB7JuXVc16J77E=; b=rr4QUzhRvH7W2s3Fp8iURRPG2tqmUr5v2BfGyFwiolGJAyqoe/xUVjzI78MbfpF0EG iy+L/Xm2i6IeHQgRIBpt9xDmRDW0puqW05ToSCLAxNOm3z+J5eMRJSq8FN8HAXEaAmfm w3NR6p0pJkMBN0AwzZlCjHAWNV4a/mog4ecOI2YqVK8dsZcwGIredggq18H/gdoFPNxk xho0ebc9rPLt+huzDr6q7Lbt25q9zqTGFugesy+89PuyBcTKMfbXnGfIBcHgUpBStuYt vXEeIr3P8gGxeNQh0A3sPwbEGCK2hbGLL87T1lXAuhvCqEqEYKuQ90AJ/DAYqWZl5YrO wQTQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1763504615; x=1764109415; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=QKvebzST2buQwrtL7F9ca9a+LG6gPYB7JuXVc16J77E=; b=lt2oiOpUo88l0rLEEtlLs0QxLn29Z7lHnRYGRIbp988Eggaud1YzoGP8KyhjP8v6JU bG0OmAo5YpChaq54WrOlXN+WSwibbAIdXCK1befZ5WF5nESu6XN3/gLsFkzpS3XiCzpR 8TjR2N8CaTcC1ak28SYBCnwYO5gpU9ym7umKUPiF20dELXXCQ/TMI7u5ZMaPuY/rp5Rv YKXc4lIlPSsfv+reUBCofVvPeLT/+/LRr9473mBzCDHaF6WqSmK4NiZtVlcSgpLAauAE dhMIc9y+Nelslt1yC6vfTCL5V2kBASYZO/orZhJPqgMV12ifUykDMTa+7ddIM/HAPbdU L8nQ== X-Forwarded-Encrypted: i=1; AJvYcCW9FyO5x4RR0pwsRY6LP+KFRYqXBYvct58hluYUUQUxRvuQg+MZSLjjmwvMZoOuvB9oSSlwQkNZ7CV2Ow0=@vger.kernel.org X-Gm-Message-State: AOJu0YxBM/+mICmKIoi+ysq22bWIQqBpYgtoGFp+HwjLds4WANL93EoX KDiDdIVtYQAzc/Fo4MrInzqUSP8KHMe7usYZUWGx+1dl3z1qe/N7lyIdcYrvGD5kIh1eLeGGNbG xx1dGmw== X-Google-Smtp-Source: AGHT+IG+97mMZM2HDntRVzkJsusKs0yMXUhQxAwl0AvkRwKpYwsDYK71pux5+Yp/6nBGQe29LFs83wtH+Kw= X-Received: from plrt3.prod.google.com ([2002:a17:902:b203:b0:297:d4ca:8805]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:f691:b0:295:6a9:cb62 with SMTP id d9443c01a7336-2986a73b4a7mr217741885ad.35.1763504614611; Tue, 18 Nov 2025 14:23:34 -0800 (PST) Reply-To: Sean Christopherson Date: Tue, 18 Nov 2025 14:23:26 -0800 In-Reply-To: <20251118222328.2265758-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251118222328.2265758-1-seanjc@google.com> X-Mailer: git-send-email 2.52.0.rc1.455.g30608eb744-goog Message-ID: <20251118222328.2265758-3-seanjc@google.com> Subject: [PATCH v2 2/4] KVM: VMX: Handle #MCs on VM-Enter/TD-Enter outside of the fastpath From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini , "Kirill A. Shutemov" Cc: kvm@vger.kernel.org, x86@kernel.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, Rick Edgecombe , Jon Kohler , Tony Lindgren Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Handle Machine Checks (#MC) that happen on VM-Enter (VMX or TDX) outside of KVM's fastpath so that as much host state as possible is re-loaded before invoking the kernel's #MC handler. The only requirement is that KVM invokes the #MC handler before enabling IRQs (and even that could _probably_ be related to handling #MCs before enabling preemption). Waiting to handle #MCs until "more" host state is loaded hardens KVM against flaws in the #MC handler, which has historically been quite brittle. E.g. prior to commit 5567d11c21a1 ("x86/mce: Send #MC singal from task work"), the #MC code could trigger a schedule() with IRQs and preemption disabled. That led to a KVM hack-a-fix in commit 1811d979c716 ("x86/kvm: move kvm_load/put_guest_xcr0 into atomic context"). Note, vmx_handle_exit_irqoff() is common to VMX and TDX guests. Cc: Tony Lindgren Cc: Rick Edgecombe Cc: Jon Kohler Signed-off-by: Sean Christopherson Reviewed-by: Binbin Wu Reviewed-by: Tony Lindgren --- arch/x86/kvm/vmx/tdx.c | 3 --- arch/x86/kvm/vmx/vmx.c | 16 +++++++++++----- 2 files changed, 11 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index e6105a527372..2d7a4d52ccfb 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1110,9 +1110,6 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, u64 ru= n_flags) if (unlikely((tdx->vp_enter_ret & TDX_SW_ERROR) =3D=3D TDX_SW_ERROR)) return EXIT_FASTPATH_NONE; =20 - if (unlikely(vmx_get_exit_reason(vcpu).basic =3D=3D EXIT_REASON_MCE_DURIN= G_VMENTRY)) - kvm_machine_check(); - trace_kvm_exit(vcpu, KVM_ISA_VMX); =20 if (unlikely(tdx_failed_vmentry(vcpu))) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index fdcc519348cd..f369c499b2c3 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7062,10 +7062,19 @@ void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu) if (to_vt(vcpu)->emulation_required) return; =20 - if (vmx_get_exit_reason(vcpu).basic =3D=3D EXIT_REASON_EXTERNAL_INTERRUPT) + switch (vmx_get_exit_reason(vcpu).basic) { + case EXIT_REASON_EXTERNAL_INTERRUPT: handle_external_interrupt_irqoff(vcpu, vmx_get_intr_info(vcpu)); - else if (vmx_get_exit_reason(vcpu).basic =3D=3D EXIT_REASON_EXCEPTION_NMI) + break; + case EXIT_REASON_EXCEPTION_NMI: handle_exception_irqoff(vcpu, vmx_get_intr_info(vcpu)); + break; + case EXIT_REASON_MCE_DURING_VMENTRY: + kvm_machine_check(); + break; + default: + break; + } } =20 /* @@ -7528,9 +7537,6 @@ fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, u64 ru= n_flags) if (unlikely(vmx->fail)) return EXIT_FASTPATH_NONE; =20 - if (unlikely((u16)vmx_get_exit_reason(vcpu).basic =3D=3D EXIT_REASON_MCE_= DURING_VMENTRY)) - kvm_machine_check(); - trace_kvm_exit(vcpu, KVM_ISA_VMX); =20 if (unlikely(vmx_get_exit_reason(vcpu).failed_vmentry)) --=20 2.52.0.rc1.455.g30608eb744-goog