From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3F36C71153 for ; Thu, 24 Aug 2023 14:27:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241620AbjHXO0h (ORCPT ); Thu, 24 Aug 2023 10:26:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241699AbjHXO00 (ORCPT ); Thu, 24 Aug 2023 10:26:26 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 496771BC6 for ; Thu, 24 Aug 2023 07:26:22 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-59294c55909so557417b3.0 for ; Thu, 24 Aug 2023 07:26:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1692887181; x=1693491981; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=GOEC2gL2vPMfrimKnsUeWbRBTwKLQLkp/XAmV7mc+hM=; b=zThywn62QCEc2gE7/6qdBaDq9/1rKpLx6RFn/awFe4rXfJOV6KKFcgLLeDA1RQnWKp 9HSRtKRV90dPkRW3JDaAB3SP/eAtxDVdsHY8i4GiuFObziA0Dsdz7Z6O1gKlANCN/dD0 SruoR9Wenx6/YuF5BTQQNs4qC7gcr4rTJqfCLexSNOOiH20ad5vvWFFPspbwLx8GFAT5 KP5A3bUNK2KlJwmzUrKcA5/TNXfo1G1rk8v5qJr1Us6VB86XUPOrmp+D0gTrVXhqIUWZ UCwdB0kJjGx1TOOnzY2Z1kLLH3GBrZFCR+HrK95SIMb+ltKBIoc6Cd3gXaMbqYfc2Byk 1Mxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692887181; x=1693491981; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=GOEC2gL2vPMfrimKnsUeWbRBTwKLQLkp/XAmV7mc+hM=; b=KJvJuiip3JIuEjtvwEtsBGe7Ek7blmT3xH2r4NVWqLcwyHSsM8UvVJvKjbNvKw0qme lQjiwJvsnXcpztljjggUD36FZ7M0kiiwF4UamaqsTUn1heUl9kIAflEpknpbDSU8rC2Q iTpwZ1cm40xUSRkmKIMawcr5yjlBzvRRdNs2SbL+JaVwsqSCUG26omUc0I+AQTwcrfpZ ODfHlWGAD8f3G/Qewqh39QRpzvXaK0LQiwG0+iYQN4LRNJ2NEo7dE5sSGfFSasiqt3a3 NmL0YdYayI57uG75+gzp+B3nZ2kppeyNvzB/WpzGyZRqG/GSV0+QcvmJ5OKs2rlagCYh t6VA== X-Gm-Message-State: AOJu0YwMIbpnQvTvEYec0PnXj3vcC6BfWONBfTx870INdE9rqjgNPTm+ WL4wtzEREtXOtow9TPiEQ38LzHaekxw= X-Google-Smtp-Source: AGHT+IGRA8onYtETZ5TVTvLafV/wVwLQi13rt/bL96OuVKnHFmkFCsfsn/0KnssV9bbTzeqokJkvsPqXgwQ= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a81:af0e:0:b0:58c:6ddd:d27c with SMTP id n14-20020a81af0e000000b0058c6dddd27cmr233466ywh.6.1692887181634; Thu, 24 Aug 2023 07:26:21 -0700 (PDT) Date: Thu, 24 Aug 2023 07:26:20 -0700 In-Reply-To: Mime-Version: 1.0 References: <20221213060912.654668-1-seanjc@google.com> <20221213060912.654668-8-seanjc@google.com> Message-ID: Subject: Re: [PATCH 7/7] KVM: VMX: Handle NMI VM-Exits in noinstr region From: Sean Christopherson To: Like Xu Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Andy Lutomirski , Thomas Gleixner , Paolo Bonzini Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Aug 24, 2023, Sean Christopherson wrote: > On Thu, Aug 24, 2023, Like Xu wrote: > > @@ -7389,6 +7382,13 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu) > > > > trace_kvm_exit(vcpu, KVM_ISA_VMX); > > > > + if ((u16)vmx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI && > > + is_nmi(vmx_get_intr_info(vcpu))) { > > + kvm_before_interrupt(vcpu, KVM_HANDLING_NMI); > > + vmx_do_nmi_irqoff(); > > + kvm_after_interrupt(vcpu); > > + } > > No, the whole point of doing NMI handling in vmx_vcpu_enter_exit() is so that NMIs > are serviced before instrumentation is enabled. > > I think the below is sufficient (untested at this point). Not quite minimal, e.g. > I'm pretty sure there's (currently) no need to snapshot IDT_VECTORING_INFO_FIELD > so early, but I can't think of any reason to wait. > > -- > From: Sean Christopherson > Date: Thu, 24 Aug 2023 06:49:36 -0700 > Subject: [PATCH] KVM: VMX: Refresh available regs and IDT vectoring info > before NMI handling > > Reset the mask of available "registers" and refresh the IDT vectoring > info snapshot in vmx_vcpu_enter_exit(), before KVM potentially handles a > an NMI VM-Exit. One of the "registers" that KVM VMX lazily loads is the > vmcs.VM_EXIT_INTR_INFO field, which is holds the vector+type on "exception > or NMI" VM-Exits, i.e. is needed to identify NMIs. Clearing the available > registers bitmask after handling NMIs results in KVM querying info from > the last VM-Exit that read vmcs.VM_EXIT_INTR_INFO, and leads to both > missed NMIs and spurious NMIs from the guest's perspective. Oof, it's not just from the guest's perspective, NMIs that are destined for host consumption will suffer the same fate.