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 323EF15E5BB; Tue, 12 May 2026 00:38:02 +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=1778546283; cv=none; b=DWEP6XkLZgt2zRLgJpuVHgVih3RTQyE+DY8W+4W6IKyVknnvHlKz/+JIl5TXjoPOrkKyja/eOnnJBroM4sbUM+XIFhsPIpfozRwomxKuK4pmBu17WUhUSml2EXX7EKoPzUtYdteI9HIR5Mc6+aABTe6l4bx+9TXvQeiuCYf8+6s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778546283; c=relaxed/simple; bh=av50ekhwDqan5HsS7/1OJVTH9wrg0R2PA52xK/hu+Bk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=m+IpW/5K08/zpfWc165XPvrnhd6ugvRTP+4VKQkOjrnGYlzNHNmKrBeHN3y3QpXA5OCo3Z6BnM5LBXtSmzqLySVmmRThqjdbZsvZfGEpbNWip+jSIj0nmUGHVtq92EssdNYY0UAXFnoilIF83My0PHvZCzB1R/xEQzdi5tGeiZc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sUYgT2rO; 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="sUYgT2rO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97CF8C2BCB0; Tue, 12 May 2026 00:38:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778546282; bh=av50ekhwDqan5HsS7/1OJVTH9wrg0R2PA52xK/hu+Bk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sUYgT2rOOOE2V9frE6zRmqJiKWWKjWjeCJkZPqRvX2a5/KYJRZmsG7FYYar/gY+tC 49tIodyjymvx6N8qzu02KYMbLSlk/YtTk0YdlX40LrYxgB14c3rKK4kBCpU+8Gap97 8S09z8YRZwdhAcqB39bPDUkQex5YBS/FNke5xSZPkwztKY24puhwr/LThatZ/uukbJ Yk1Me/AjTeE5Hx0FpkaLm2/EHXHrpPuX4EhQgRq5VFY1zjOxvFAXu8gIi6Ja/Ir4Lq 4nicsglJhAWUHdzPU+zsyYwRIhP6MZKvRKMmCU8aFZOPqH8lM96ZnGBTmzJgdKLe+w T6xDfPQKIpUNQ== Date: Tue, 12 May 2026 00:38:01 +0000 From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Maxim Levitsky , David Kaplan Subject: Re: [PATCH v2] KVM: nSVM: Never use L0's PAUSE loop exiting while L2 is running Message-ID: References: <20260508213321.373309-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260508213321.373309-1-seanjc@google.com> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index e7fdd7a9c280..ac21f402c1ca 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -913,7 +913,12 @@ static void grow_ple_window(struct kvm_vcpu *vcpu) > struct vmcb_control_area *control = &svm->vmcb->control; > int old = control->pause_filter_count; > > - if (kvm_pause_in_guest(vcpu->kvm)) > + /* > + * While running L2, KVM should intercept PAUSE if and only if L1 wants > + * to intercept PAUSE, and L1's intercept should take priority, i.e. > + * KVM should never handle a PAUSE intercept from L2. > + */ > + if (WARN_ON_ONCE(is_guest_mode(vcpu) || kvm_pause_in_guest(vcpu->kvm))) > return; I initially thought putting kvm_pause_in_guest() inside the WARN_ON_ONCE() was a mistake, but I don't think it is. KVM only intercepts PAUSE if kvm_pause_in_guest() is false, so grow_ple_window() should never be called. But I think this applies even without this patch, right? Maybe would be clearer to do WARN_ON_ONCE(kvm_pause_in_guest()) in one commit and then add is_guest_mode() here? > > control->pause_filter_count = __grow_ple_window(old, > @@ -934,7 +939,7 @@ static void shrink_ple_window(struct kvm_vcpu *vcpu) > struct vmcb_control_area *control = &svm->vmcb->control; > int old = control->pause_filter_count; > > - if (kvm_pause_in_guest(vcpu->kvm)) > + if (is_guest_mode(vcpu)) > return; > > control->pause_filter_count = > > base-commit: 6d35786de28116ecf78797a62b84e6bf3c45aa5a > -- > 2.54.0.563.g4f69b47b94-goog > >