From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id E5D3F72612; Fri, 24 Oct 2025 15:05:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761318320; cv=none; b=DDMJPKyoHJ/EkI8zZwar8VCrr08y3lGH3sh1nLATAsytIP1j7LEIFP2bdPWLPRzyflEDI7Ji8WaiS7PX7afBCmv5u1VT25ksXUQfImesryaCqA+wvYhQGGaIx5T7LdUFRPo8s4wDIZLYZ3ylj3B+U6yMC6A1R+oskGDHZofTDbo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761318320; c=relaxed/simple; bh=mFsntFKm3sLCSsUTazR6Zz09gRvrPjOBy+0/EZ6kZlE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LUokSi4+hsWWbGeiCnn6I3msHAsC2CjnTXFPWIXPc8U67Bbd0fClQRnUIzd/3nOVZPiX7M0cjiHXO/8zsVVhSFuwEb56OXowIsn6iG5jtvn0+WMiId3xBW47audua5W8fh9mE2ameItS1U4qu2dRQXEcClPYM+1MvJrl2YaQ/hY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 29D6E14BF; Fri, 24 Oct 2025 08:05:10 -0700 (PDT) Received: from [10.57.67.38] (unknown [10.57.67.38]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 519063F63F; Fri, 24 Oct 2025 08:05:10 -0700 (PDT) Message-ID: <6ed9f404-9939-4e9f-b5aa-4253bef46df1@arm.com> Date: Fri, 24 Oct 2025 17:05:07 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 11/13] x86/xen: use lazy_mmu_state when context-switching To: David Woodhouse , David Hildenbrand , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Alexander Gordeev , Andreas Larsson , Andrew Morton , Boris Ostrovsky , Borislav Petkov , Catalin Marinas , Christophe Leroy , Dave Hansen , "David S. Miller" , "H. Peter Anvin" , Ingo Molnar , Jann Horn , Juergen Gross , "Liam R. Howlett" , Lorenzo Stoakes , Madhavan Srinivasan , Michael Ellerman , Michal Hocko , Mike Rapoport , Nicholas Piggin , Peter Zijlstra , Ryan Roberts , Suren Baghdasaryan , Thomas Gleixner , Vlastimil Babka , Will Deacon , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, xen-devel@lists.xenproject.org, x86@kernel.org References: <20251015082727.2395128-1-kevin.brodsky@arm.com> <20251015082727.2395128-12-kevin.brodsky@arm.com> <348e5f1c5a90e4ab0f14b4d997baf7169745bf04.camel@infradead.org> Content-Language: en-GB From: Kevin Brodsky In-Reply-To: <348e5f1c5a90e4ab0f14b4d997baf7169745bf04.camel@infradead.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 24/10/2025 16:47, David Woodhouse wrote: > On Thu, 2025-10-23 at 22:06 +0200, David Hildenbrand wrote: >> On 15.10.25 10:27, Kevin Brodsky wrote: >>> We currently set a TIF flag when scheduling out a task that is in >>> lazy MMU mode, in order to restore it when the task is scheduled >>> again. >>> >>> The generic lazy_mmu layer now tracks whether a task is in lazy MMU >>> mode in task_struct::lazy_mmu_state. We can therefore check that >>> state when switching to the new task, instead of using a separate >>> TIF flag. >>> >>> Signed-off-by: Kevin Brodsky >>> --- >> >> Looks ok to me, but I hope we get some confirmation from x86 / xen >> folks. > > I know tglx has shouted at me in the past for precisely this reminder, > but you know you can test Xen guests under QEMU/KVM now and don't need > to actually run Xen? Has this been boot tested? I considered boot-testing a Xen guest (considering the Xen-specific changes in this series), but having no idea how to go about it I quickly gave up... Happy to follow instructions :) - Kevin