From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (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 11AF554F82 for ; Mon, 8 Jan 2024 17:38:05 +0000 (UTC) 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="1yff7LPS" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-dbcd9f4396eso2218560276.0 for ; Mon, 08 Jan 2024 09:38:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1704735485; x=1705340285; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=CeET3LCD9y8mkzdt1n7zEREdExwaFpwQOr0tIUhzNgg=; b=1yff7LPSiX+Lx9usqzs3Ck7+fY59unWKCz9VwGMAY7w4RCgqBd4FImn/dqQmKvU5GY ajXMHZrEntZ51vVZxopVlZe5Q7R5obWH7o5C+BM9uQ1ZuKrymWuhumXUjrRIbFCErfk+ vZyPR3/rLP/6NslI9e0++PXoVzmWHLS4fW7gJUsqyyacTecmi3ia12nujaARyRYsgYbs nvuGZ42DA06RAFY4RxpQ6k7jABOgzdMbYP/2Kc3mryEg1QH07euEWRt572EnypLl1SMZ T3XYmgsHwFkvAIW5DaKtX4OJsfK8HtUMAH9WKsnCTL92s/38z2C2FTteRDltXZl8qyRZ WoxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704735485; x=1705340285; 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=CeET3LCD9y8mkzdt1n7zEREdExwaFpwQOr0tIUhzNgg=; b=oxG8zF9Sb9HArNiM70AuEZpOqgyyx0nFnX6FFyFWsakj3yJWlrOAW7QPk++rqVQlFf cmiUUAncByvuWf9Zfv7jTaZBS8gL9CjlUHcXau+NWn5aThbYP3Zdce9GhRWPfkEg/IW7 aA6NRkTE0PZSlWlukltyTK6/zmsCXAO6/2oakK07zvs0fEEuEnf6M94arI3zpJE9o/ss 42eY6aV9mVxEn+23ZNJhS/XO4ZwHZm2chp1mOmtSvumQOlbRvpgAhSP61L4js2uBkf7E BSl34oFx+z9vqyfTMAnbYH0KBJ21CQqBUH+iokXOGgUfvBDxlXldantG/jogDdujTG9m wGjg== X-Gm-Message-State: AOJu0YwZSCduVM/oY/ZTW/6i/NaTuuf9Jb3U7jVodxYySlB+Uvi+JBNo Ygt+j5wkKMb0OrIjmf4vnXCO/oizArmnuL1+Zw== X-Google-Smtp-Source: AGHT+IFY9eZr/TVBtL10OzQOm/ftwdCvRmuFITZVupfSGA0iFM+gy+JvMfFVxN4DNX5NCzguKOIVEMkCDaM= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:ba86:0:b0:dbe:9f60:c72f with SMTP id s6-20020a25ba86000000b00dbe9f60c72fmr1636784ybg.4.1704735485088; Mon, 08 Jan 2024 09:38:05 -0800 (PST) Date: Mon, 8 Jan 2024 09:38:03 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240103075343.549293-1-ppandit@redhat.com> Message-ID: Subject: Re: [PATCH] KVM: x86: make KVM_REQ_NMI request iff NMI pending for vcpu From: Sean Christopherson To: Prasad Pandit Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Prasad Pandit Content-Type: text/plain; charset="us-ascii" On Mon, Jan 08, 2024, Prasad Pandit wrote: > On Wed, 3 Jan 2024 at 13:24, Prasad Pandit wrote: > > kvm_vcpu_ioctl_x86_set_vcpu_events() routine makes 'KVM_REQ_NMI' > > request for a vcpu even when its 'events->nmi.pending' is zero. > > Ex: > > qemu_thread_start > > kvm_vcpu_thread_fn > > qemu_wait_io_event > > qemu_wait_io_event_common > > process_queued_cpu_work > > do_kvm_cpu_synchronize_post_init/_reset > > kvm_arch_put_registers > > kvm_put_vcpu_events (cpu, level=[2|3]) > > > > This leads vCPU threads in QEMU to constantly acquire & release the > > global mutex lock, delaying the guest boot due to lock contention. > > Add check to make KVM_REQ_NMI request only if vcpu has NMI pending. > > > > Fixes: bdedff263132 ("KVM: x86: Route pending NMIs from userspace through process_nmi()") > > Signed-off-by: Prasad Pandit > > --- > > arch/x86/kvm/x86.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index 1a3aaa7dafae..468870450b8b 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -5405,7 +5405,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu, > > if (events->flags & KVM_VCPUEVENT_VALID_NMI_PENDING) { > > vcpu->arch.nmi_pending = 0; > > atomic_set(&vcpu->arch.nmi_queued, events->nmi.pending); > > - kvm_make_request(KVM_REQ_NMI, vcpu); > > + if (events->nmi.pending) > > + kvm_make_request(KVM_REQ_NMI, vcpu); > > } > > static_call(kvm_x86_set_nmi_mask)(vcpu, events->nmi.masked); > > -- > > 2.43.0 > > Ping...! This is on my list of things to grab for 6.8, I'm just waiting for various pull requests to fully land in order to simplify my branch management.