From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 9DEBB3E1CFB; Wed, 16 Sep 2026 18:58:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789585155; cv=none; b=Edgy3ctmhWkox11dulrgXcabRCxcMRGx/hqnGLlAwihxhPtOfo6O+QfB88UcAyzGaQPEk5E4k0u7QmiVKkwbPlADP+PxD30el/bHGzJGBynylf7rOOXNswCXfktKOIMM35qaZQF0n9xvRrgODk6wHOqMMF3nmM0aIrN9mGq/Upc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789585155; c=relaxed/simple; bh=VSWJFFyILOifULHYldTAkG+40oNQYoyuQxpyJOfRaKo=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=sZE8xUMgmo14lHpVXXuQdg/5bTlwK0c7i2oUvs6EdZD7zjYzkVyrNymqGhFdKZ6pSQIINVutKWx3/gTPZ2C9OKHFmqsKT1+MfuEN4SN2T2P3EVffNSTQG+mn/UNbjmmdTSbSpeDUZXju4heEt55KE5iTrVqm2pPh+mnSPkm5yVM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dpKfeOdn; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dpKfeOdn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 575CF1F000FF; Wed, 16 Sep 2026 18:58:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789585127; bh=lSvr0vCtdCumQova2+QTaGAW1CeluERBIU1FmP9NgV0=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=dpKfeOdnhJbQOBnw3SyHypTt1bwo3khu9OjlnaFMto0eI+LryvCcytPSjazdhOHUR s4du1cwq3DXECxApHbs7cf/wMeptDnEdlt2Pclae5BtOwLmGVkqOmtMcI0ZzkNUwTL 9YWSexTWum8n8WNCqEbnlTR40tO0Qrml0kRiC5M5x+wSbM14AnTazL5yCSRNfjugqy JCXx1cKYMi8Z3Tti0pRbkYFQY0g9nmG5XSSThdECoh5+J5VCB4MTJdVcYvfjECDfap FnkMzxpiuQfqYa0TZAX1sbBJEKIfu8jryKFSikfQZ4dfSWI8Qw0+FhRqLQhSc0p5xy mjrO8itBp9hWg== From: Pratyush Yadav To: David Matlack Cc: Pratyush Yadav , Zhu Yanjun , kexec@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, Adithya Jayachandran , Alexander Graf , Alex Williamson , Bjorn Helgaas , Chris Li , David Rientjes , Jacob Pan , Jason Gunthorpe , Jonathan Corbet , Josh Hilke , Leon Romanovsky , Lukas Wunner , Mike Rapoport , Parav Pandit , Pasha Tatashin , Pranjal Shrivastava , Saeed Mahameed , Samiullah Khawaja , Shuah Khan , Vipin Sharma , William Tu , Yi Liu Subject: Re: [PATCH v8 03/12] PCI: liveupdate: Track incoming preserved PCI devices In-Reply-To: (David Matlack's message of "Wed, 16 Sep 2026 11:31:17 -0700") References: <20260728221007.2098560-1-dmatlack@google.com> <20260728221007.2098560-4-dmatlack@google.com> <2vxzcxud6ol3.fsf@kernel.org> Date: Wed, 16 Sep 2026 20:58:40 +0200 Message-ID: <2vxz5x056n1b.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Wed, Sep 16 2026, David Matlack wrote: > On Wed, Sep 16, 2026 at 11:25=E2=80=AFAM Pratyush Yadav wrote: >> >> On Wed, Sep 16 2026, David Matlack wrote: >> >> > On Tue, Sep 15, 2026 at 8:31=E2=80=AFPM Zhu Yanjun wrote: >> >> =E5=9C=A8 2026/7/28 15:09, David Matlack =E5=86=99=E9=81=93: >> > >> >> > CONFIG_64BIT is now required to enable CONFIG_PCI_LIVEUPDATE so tha= t the >> >> > domain and bdf can be guaranteed to fit in an unsigned long and be = used >> >> > as the xarray key. >> > >> >> > diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig >> >> > index 3781e2b5f095..8af20f558086 100644 >> >> > --- a/drivers/pci/Kconfig >> >> > +++ b/drivers/pci/Kconfig >> >> > @@ -273,7 +273,7 @@ config VGA_ARB_MAX_GPUS >> >> > >> >> > config PCI_LIVEUPDATE >> >> > bool "PCI Live Update Support" >> >> > - depends on PCI && LIVEUPDATE >> >> > + depends on PCI && LIVEUPDATE && 64BIT >> >> >> >> One question about adding 64BIT to the dependency: >> >> >> >> As I understand it, enabling CONFIG_64BIT essentially means that we a= re >> >> building a 64-bit kernel, and a 32-bit architecture cannot normally >> >> enable CONFIG_64BIT. >> >> >> >> If that is the case, would depends on 64BIT be necessary here? Or is = PCI >> >> Live Update already inherently restricted to 64-bit architectures by = the >> >> existing LIVEUPDATE/architecture configuration, so that this dependen= cy >> >> would be redundant? >> >> >> >> If this problem has already discussed, I am very sorry about this. >> > >> > The necessity is that the PCI core needs to store more than 32-bits in >> > the unsigned long xarray key (see the snippet above). The dependency >> > on CONFIG_64BIT ensures that unsigned long is big enough. We could >> > probably remove the dependency but I would rather wait until someone >> > with a 32-bit build has a real use-case for using PCI_LIVEUPDATE >> > before putting any effort into it. >> >> KHO or live update themselves don't support 32-bit platforms and there >> are no plans to do so either. So I don't think you even need to have a >> dependency on 64BIT in PCI_LIVEUPDATE. Only 64 bit architectures define >> ARCH_SUPPORTS_KEXEC_HANDOVER, so PCI_LIVEUPDATE and others indirectly >> inherit the dependency. >> >> If you'd like to be extra safe, then probably you should add a >> dependency to 64BIT in KEXEC_HANDOVER directly. Though I think that can >> be a separate patch independent from this series. > > It should be in both places then. PCI_LIVEUPDATE explicitly requires > 64BIT for its own use of unsigned long, so it should have an explicit > dependency. If KEXEC_HANDOVER requires 64-bit for its own specific > purposes, then it should have an explicit Kconfig dependency as well. > That way if and when someone wants to add 32-bit support we know > exactly which configs need to add support. Well, I don't think we are ever adding 32-bit support. Most 32-bit support in the kernel is being deprecated or removed, so I really don't think it makes much sense to extend KHO/live update to 32-bit architectures. But anyway, if you'd like to explicitly mark PCI as needing 64-bit, that sounds fine too in the very very unlikely event we do add 32-bit support. --=20 Regards, Pratyush Yadav