From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (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 6FF9F33E350 for ; Thu, 30 Oct 2025 22:42:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761864177; cv=none; b=qaiZabOO8zbKH9mX9K0dZevFz33Qq1hHZkOHzQz2M5y5hMO/3ZdPumGYy+aO15t1XkH9ffcPYh1PLDF0ndz/de48FHnXdU5cFG6NUOsXJyu7d5dmTYG5UxgUdwZFQMjz8CrTNyz8KL5zDMBzYezEryddAYT0uAV0UGe6B7P4sBY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761864177; c=relaxed/simple; bh=MchINskavBlkrWKmsZW/V/NyWaLoR3Fo1XQuVOdWnzU=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=T6pw/Bvh1nmOc0dtl6uTUHkkChjIWZi4ZBv2RbA6mOBncmcWGlqmE/ym3SN0H3iHGefzka0/q0+ruX9vcfDHOtExNk1l0xGJDtZjk+prYV2aqtWqvkjqNmckk5hAAQZ3Bfpm2cahmmSFKbioR2lDpWyKexAgwRWPVJSXEmN5djQ= 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=w2CQc3uT; arc=none smtp.client-ip=209.85.216.73 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="w2CQc3uT" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-3407734d98bso719170a91.3 for ; Thu, 30 Oct 2025 15:42:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1761864175; x=1762468975; 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=RzJXvA2qL3oBmeCAhgbR20GHWytyM2jCig5eMpHPXQk=; b=w2CQc3uTqtONunN+PyPkmQVUtI4sYB0GQvZuT5HOPb8mKxngdl/Vtu3uazHidjJ0eR 2jsMsdcHEJqe1JiDbvXiY1+yi47xpqPAA+SC0DQCBFI2FGcJETZNSzfvfXDymP4iMitP aIHqyRt9qI9JOaC0qu1cabzTBxWQPSU32Ao9ah5iQ8nSxZ9EB0vqUDart3uozN+47deD 6hQu2MX2GFNWNWTWI57R5LZ0VF3Gc5bQHvO8rhGbfcKfIhU+IwJOEHasFEwK1ayH74Of MJN4WmUpmFH2RhpxO0BY3zzLujhVJMFQkoitpLSiCDhg3pdgxOU2a30j/MVcH22TnQ6M Awfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761864175; x=1762468975; 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=RzJXvA2qL3oBmeCAhgbR20GHWytyM2jCig5eMpHPXQk=; b=uZi4Rm6cST47MPDu5J7AhtR4cLCHR9hF/hmkMSrU4DXtotaBUHMeIC7uIZmautwt7/ J8c4FRFg4UO4cD1BABte69btWxN6JJ3DM4MFFRsotvduXxVtAoMkmPZSqC//vS+cElLw XBwPdLXcTyQapFJYF5dBGRLjXJtnypwByL8GNE2J6QLj412r2EG+H7KQw7ch+D0iYkZi 6PZFyOr5u0yrA8RY1WMGLYl0UA1MbPyAUCZJroSAeT9ASiZdRliDBUDPZdbSPmTQsDoz 5GC2jFgT5VyAXp/cQS0+pxImpWmy2fvcqp6bkuasGzSZMHqYui9QkJ+fqNM0dSIr69pt Li5Q== X-Gm-Message-State: AOJu0Ywo/sd7glyNnfxsrBXT9LfBCb1bBLQJ/46pk+wpEGpiazaJFfbJ pM0SLmHi6MniFhfBVz6jeM5DetqBMYEV4lLVx1v0sNSWyvnfwYdqITh7xTmlEE/3CUpTqsKQdVl 1yO4X+w== X-Google-Smtp-Source: AGHT+IGTW7/+BlUHW51xmkfkplp3sSIcQ+cUhORPp1pYopyj5vl7hP44CWO33PujFVasNhIynwLieXXQRjA= X-Received: from pjbms9.prod.google.com ([2002:a17:90b:2349:b0:33d:69cf:1f82]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:2f87:b0:33e:30e8:81cb with SMTP id 98e67ed59e1d1-34082fd8a5emr1932559a91.13.1761864174630; Thu, 30 Oct 2025 15:42:54 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 30 Oct 2025 15:42:44 -0700 In-Reply-To: <20251030224246.3456492-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251030224246.3456492-1-seanjc@google.com> X-Mailer: git-send-email 2.51.1.930.gacf6e81ea2-goog Message-ID: <20251030224246.3456492-3-seanjc@google.com> Subject: [PATCH 2/4] KVM: VMX: Handle #MCs on VM-Enter/TD-Enter outside of the fastpath From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jon Kohler 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"). Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/main.c | 13 ++++++++++++- arch/x86/kvm/vmx/tdx.c | 3 --- arch/x86/kvm/vmx/vmx.c | 3 --- 3 files changed, 12 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c index 0eb2773b2ae2..1beaec5b9727 100644 --- a/arch/x86/kvm/vmx/main.c +++ b/arch/x86/kvm/vmx/main.c @@ -608,6 +608,17 @@ static void vt_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, vmx_load_mmu_pgd(vcpu, root_hpa, pgd_level); } +static void vt_handle_exit_irqoff(struct kvm_vcpu *vcpu) +{ + if (unlikely((u16)vmx_get_exit_reason(vcpu).basic == EXIT_REASON_MCE_DURING_VMENTRY)) + kvm_machine_check(); + + if (is_td_vcpu(vcpu)) + return; + + return vmx_handle_exit_irqoff(vcpu); +} + static void vt_set_interrupt_shadow(struct kvm_vcpu *vcpu, int mask) { if (is_td_vcpu(vcpu)) @@ -969,7 +980,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = { .load_mmu_pgd = vt_op(load_mmu_pgd), .check_intercept = vmx_check_intercept, - .handle_exit_irqoff = vmx_handle_exit_irqoff, + .handle_exit_irqoff = vt_op(handle_exit_irqoff), .update_cpu_dirty_logging = vt_op(update_cpu_dirty_logging), diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 326db9b9c567..a2f6ba3268d1 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1069,9 +1069,6 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags) if (unlikely((tdx->vp_enter_ret & TDX_SW_ERROR) == TDX_SW_ERROR)) return EXIT_FASTPATH_NONE; - if (unlikely(vmx_get_exit_reason(vcpu).basic == EXIT_REASON_MCE_DURING_VMENTRY)) - kvm_machine_check(); - trace_kvm_exit(vcpu, KVM_ISA_VMX); if (unlikely(tdx_failed_vmentry(vcpu))) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 1021d3b65ea0..123dae8cf46b 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7527,9 +7527,6 @@ fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags) if (unlikely(vmx->fail)) return EXIT_FASTPATH_NONE; - if (unlikely((u16)vmx_get_exit_reason(vcpu).basic == EXIT_REASON_MCE_DURING_VMENTRY)) - kvm_machine_check(); - trace_kvm_exit(vcpu, KVM_ISA_VMX); if (unlikely(vmx_get_exit_reason(vcpu).failed_vmentry)) -- 2.51.1.930.gacf6e81ea2-goog