From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C54FFC88E72 for ; Thu, 17 Sep 2026 20:19:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:References: List-Owner; bh=FVPFyILB0p9mKi052GhepayT1vMbxqjB1Nhk/upvblM=; b=p5vaaysRFCQeOp JYsFzKnvrE5jXO3cmkHg64VbUwO/jWgHiMFOBeAvjRxQWiWuC7WpeP2usmX8S8XA1uBa+sYigU/n0 zK/f0uO7152Gy1VK4DyEASK50k2ZNOlKYGVCKHad4MKY03necLwA/BeGIN3hm3CS8d68Ybo9lqAli zoBVmRV5vQNgnaK4nT9nEUFZ7JY4NxeKoa0ovrAUDcyRAh9qRzmaBvxJBuZKQNYJ7ntNRtlFwW5cq qJhg+KICZVu8rGad26q8JLpm2QAGGYOnHIyQSNHw+6CsPvPARJrqTpoAR+Sk6XojayyCSiuZmgu5g z6wFuAsnzSdltrUWpIdw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x7IaI-0000000CPu0-3geR; Thu, 17 Sep 2026 20:19:54 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x7IaH-0000000CPtq-40NR for kexec@lists.infradead.org; Thu, 17 Sep 2026 20:19:53 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 5DA3442A50; Thu, 17 Sep 2026 20:19:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 177331F000FF; Thu, 17 Sep 2026 20:19:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789676393; bh=FVPFyILB0p9mKi052GhepayT1vMbxqjB1Nhk/upvblM=; h=Date:From:To:Cc:Subject:In-Reply-To; b=fPn5Yy6FfiqKTmfjU5oYceM12GCmiYpT11w/2EyEPdKZGB9CPcBNkVv2+BwFLzu6X xSgkGQj5+WhLzGvcmRurhfvuOQGHvSLSKl4teDAJZ6QR/QG7VnV959jPcTz+HVEaZK CuD8XS5L28gUkvAbrICdalmnnCwxmYFcPuyhzJDJRcJ2dL8dpzKDBT7Z38/9T65arE LY8nGXBX//YUlL/TndeGkCuR1dbAH8rbGwzFuTEWxVYd14ZqNgn+y/iXdiTaJOcVDu NcVTytHagvF9lKoqQdw5+GoOIioEKAtSHIhUTx/SJFFATlpqz1u3d3zNwsKQDDY+v+ SECBXMxIYkoGg== Date: Thu, 17 Sep 2026 15:19:52 -0500 From: Bjorn Helgaas To: David Matlack Cc: 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 , Pratyush Yadav , Saeed Mahameed , Samiullah Khawaja , Shuah Khan , Vipin Sharma , William Tu , Yi Liu Subject: Re: [PATCH v8 11/12] PCI: liveupdate: Do not disable bus mastering on preserved devices during kexec Message-ID: <20260917201952.GA1049400@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260728221007.2098560-12-dmatlack@google.com> X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On Tue, Jul 28, 2026 at 10:10:05PM +0000, David Matlack wrote: > Do not disable bus mastering on outgoing preserved devices during > pci_device_shutdown() for kexec. > > Preserved devices must be allowed to perform memory transactions during > a Live Update to ensure continuous operation. Clearing the bus > mastering bit would prevent these devices from issuing any memory > requests while the new kernel boots. > > Because bridges upstream of preserved endpoint devices are also > automatically preserved, this change also avoids clearing bus mastering > on them. This is critical because clearing bus mastering on an upstream > bridge prevents the bridge from forwarding memory requests upstream (i.e. > it would prevent the endpoint device from accessing system RAM and doing > peer-to-peer transactions with devices not downstream of the bridge). > > Reviewed-by: Pranjal Shrivastava > Reviewed-by: Pasha Tatashin > Signed-off-by: David Matlack Reviewed-by: Bjorn Helgaas > --- > drivers/pci/liveupdate.c | 11 +++++++++++ > drivers/pci/liveupdate.h | 6 ++++++ > drivers/pci/pci-driver.c | 7 +++++-- > 3 files changed, 22 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/liveupdate.c b/drivers/pci/liveupdate.c > index 65bcecb1b64e..32b73ebf71f7 100644 > --- a/drivers/pci/liveupdate.c > +++ b/drivers/pci/liveupdate.c > @@ -132,6 +132,10 @@ > * * The PCI core adopts ARI Forwarding Enable on all bridges with downstream > * preserved devices to ensure that all preserved devices on the bridge's > * secondary bus are addressable after the Live Update. > + * > + * * The PCI core does not disable bus mastering on outgoing preserved devices > + * during kexec. This allows preserved devices to issue memory transactions > + * throughout the Live Update. > */ > > #define pr_fmt(fmt) "PCI: liveupdate: " fmt > @@ -879,6 +883,13 @@ int pci_liveupdate_adopt_ari(struct pci_dev *dev) > return 0; > } > > +bool pci_liveupdate_is_outgoing(struct pci_dev *dev) > +{ > + guard(rwsem_read)(&pci_liveupdate.rwsem); > + pci_WARN_ONCE(dev, !dev->liveupdate.frozen, "Preservation status is unstable!\n"); > + return dev->liveupdate.outgoing; > +} > + > /** > * pci_liveupdate_is_incoming() - Check if a device is incoming-preserved > * @dev: The PCI device to check > diff --git a/drivers/pci/liveupdate.h b/drivers/pci/liveupdate.h > index 49d07fd02132..9c31fb60207d 100644 > --- a/drivers/pci/liveupdate.h > +++ b/drivers/pci/liveupdate.h > @@ -20,6 +20,7 @@ void pci_liveupdate_scan_bridge_end(struct pci_dev *dev); > void pci_liveupdate_cache_adopted_acs_controls(struct pci_dev *dev); > int pci_liveupdate_enable_adopted_acs_controls(struct pci_dev *dev); > int pci_liveupdate_adopt_ari(struct pci_dev *dev); > +bool pci_liveupdate_is_outgoing(struct pci_dev *dev); > #else > static inline void pci_liveupdate_setup_device(struct pci_dev *dev) > { > @@ -55,6 +56,11 @@ static inline int pci_liveupdate_adopt_ari(struct pci_dev *dev) > { > return -EINVAL; > } > + > +static inline bool pci_liveupdate_is_outgoing(struct pci_dev *dev) > +{ > + return false; > +} > #endif > > #endif /* DRIVERS_PCI_LIVEUPDATE_H */ > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > index 51616e4327d3..47cb3dcaa927 100644 > --- a/drivers/pci/pci-driver.c > +++ b/drivers/pci/pci-driver.c > @@ -546,11 +546,14 @@ static void pci_device_shutdown(struct device *dev) > /* > * If this is a kexec reboot, turn off Bus Master bit on the > * device to tell it to not continue to do DMA. Don't touch > - * devices in D3cold or unknown states. > + * devices being preserved for Live Update or in D3cold or > + * unknown states. > + * > * If it is not a kexec reboot, firmware will hit the PCI > * devices with big hammer and stop their DMA any way. > */ > - if (kexec_in_progress && (pci_dev->current_state <= PCI_D3hot)) > + if (kexec_in_progress && !pci_liveupdate_is_outgoing(pci_dev) && > + pci_dev->current_state <= PCI_D3hot) > pci_clear_master(pci_dev); > } > > -- > 2.55.0.487.gaf234c4eb3-goog >