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 8D25F19D880; Fri, 3 Oct 2025 17:30:27 +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=1759512627; cv=none; b=F/doD1TK/aWtPfTkd2tOkOz6pucfpF6soRXMlzkGNlrX9goboADmEktyZIAAUVeTEsfjxDeaIUT04mJ3PgEt3VoF1Czw0PUbbF6SvCcMbJPdQsWA4Hyy/Dc8bZ5uh/lv/ZHpaI4JS4pucuuufwQnwlEsViSYCosoZA4AEIYcjlc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759512627; c=relaxed/simple; bh=bKcFHluIfrETRlHficKsjNssD6yv+m3BNXXEAZK5oWg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=V4c6kU0Re0ThV1VNyAXIdzt9um/KOmMtkYEdG7nSdsiDUEJ2XzWl5xKVE7bCxanHZ2fIv52qhZcMgIalRon9Q5dfJFkW8DLXRghoQ7CjNAWnmLaGyn4Jv6HqGhilSo1oieCX+7crhOAXdWtc3MCdFoqmW47h4O7S5JXNge2YrAw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b8VJeqEq; 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="b8VJeqEq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CECD7C4CEFB; Fri, 3 Oct 2025 17:30:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1759512627; bh=bKcFHluIfrETRlHficKsjNssD6yv+m3BNXXEAZK5oWg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=b8VJeqEqJRiQImLzV8sXGLQCh9HRup33B8JbRgUXQprFKzjo/JGjhFemxIWGFx0WY n/arZulzWai21cCRYSBti7yjQre8olHYzBiQ3GaPIWpDDMJNbpWMWJiWNJDxuj13hA 6MGc6+s60vcQTSdABQr+P6LnAI/Tfxn+Ypnch9mlOnWNqdifeAMsdEL8x9tGVefljT Nmnd2HMCIHkkgS/MTj+Q8IpmlYMzWqdyXUPPt//++e7v5AdcP9DHjfCzydXmuQY6MK E/BbT6XMQUZv5uvFkOgSzdyDFr/gQ7IOyXrJTK/Plh8uE2Yrny8d50Ip0EV+fKNdcl BmVpRQX1I5lXQ== Date: Fri, 3 Oct 2025 17:30:25 +0000 From: Wei Liu To: Stanislav Kinsburskii Cc: Nuno Das Neves , linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, prapal@linux.microsoft.com, easwar.hariharan@linux.microsoft.com, tiala@microsoft.com, anirudh@anirudhrb.com, paekkaladevi@linux.microsoft.com, kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com Subject: Re: [PATCH v4 0/5] mshv: Fixes for stats and vp state page mappings Message-ID: <20251003173025.GA1161403@liuwe-devbox-debian-v2.local> References: <1758903795-18636-1-git-send-email-nunodasneves@linux.microsoft.com> <96009fb8-0ad6-4e5b-8656-af78874a5605@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-hyperv@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: On Fri, Oct 03, 2025 at 09:31:41AM -0700, Stanislav Kinsburskii wrote: > On Mon, Sep 29, 2025 at 11:19:51AM -0700, Nuno Das Neves wrote: > > On 9/26/2025 4:12 PM, Stanislav Kinsburskii wrote: > > > On Fri, Sep 26, 2025 at 09:23:10AM -0700, Nuno Das Neves wrote: > > >> There are some differences in how L1VH partitions must map stats and vp > > >> state pages, some of which are due to differences across hypervisor > > >> versions. Detect and handle these cases. > > >> > > > > > > I'm not sure that support for older and actully broken versions on > > > hypervisor need to be usptreamed, as these versions will go away sooner > > > or later and this support will become dead weight. > > > > > As far as I know, these changes are relevant for shipped versions of the > > hypervisor - they are not 'broken' except in some very specific cases > > (live migration on L1VH, I think?) > > > > I'm not sure I understand what "shipped version" of hypervisor actually > is. > As of today, the hypervisor is close source and the only product where > it's used is Azure. In Azure, the older versions of hypervisor are > replaced with newer on regular basis. > > > The hypervisor team added a feature bit for these changes so that both old > > and new versions of these APIs can be supported. > > > > > I think we should upstrem only the changes needed for the new versiong > > > of hypervisors instead and carry legacy support out of tree until it > > > becomes obsoleted. > > > > > Which version do you suggest to be the cutoff? > > > > I'd prefer to support as many versions of the hypervisor as we can, as > > long as they are at all relevant. We can remove the support later. > > Removing prematurely just creates friction. Inevitably some users will > > find themselves running on an older hypervisor and then it just fails > > with a cryptic error. This includes myself, since I test L1VH on Azure > > which typically has older hypervisor versions. > > > > Given that these changes are expected to land to a newly released > kernel, it will take time until this kernel gets to production. At that > moment it's highly likley that the older versions of hypervisor you are > trying to support here will be gone for good. No. This is not 100% certain. The schedule is outside of our control. Who knows if there is a specialized Azure cluster that is not updated for some reason. Interested parties have already started experimenting with this new setup. I just point them to the upstream tree whenever I can. > Even if they won't be gone, they will be obsoleted and intended to be > replaced which effecitively makes this support of older versions a > dead weight, which - if needed to be caried - is cleaner to keep in house > and drop when apporiate than keeping in the upstream code base. > While the maintenance burden argument generally applies, the burden in this case is not big. It is totally fine to have the code. Wei > Thanks, > Stas > > > Nuno > > > > > Thanks, > > > Stanislav > > > > > >