linux-kernel - [RFC PATCH 11/21] vfio/pci: Skip clearing bus master on live update device during kexec

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Message-ID: <20251018000713.677779-12-vipinsh@google.com>
Date: Fri, 17 Oct 2025 17:07:03 -0700
From: Vipin Sharma <vipinsh@...gle.com>
To: bhelgaas@...gle.com, alex.williamson@...hat.com, pasha.tatashin@...een.com, 
	dmatlack@...gle.com, jgg@...pe.ca, graf@...zon.com
Cc: pratyush@...nel.org, gregkh@...uxfoundation.org, chrisl@...nel.org, 
	rppt@...nel.org, skhawaja@...gle.com, parav@...dia.com, saeedm@...dia.com, 
	kevin.tian@...el.com, jrhilke@...gle.com, david@...hat.com, 
	jgowans@...zon.com, dwmw2@...radead.org, epetron@...zon.de, 
	junaids@...gle.com, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, 
	kvm@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	Vipin Sharma <vipinsh@...gle.com>
Subject: [RFC PATCH 11/21] vfio/pci: Skip clearing bus master on live update
 device during kexec

Set skip_kexec_clear_master on live update prepare() so that the device
participating in live update can continue to perform DMA during kexec
phase.

Signed-off-by: Vipin Sharma <vipinsh@...gle.com>
---
 drivers/vfio/pci/vfio_pci_liveupdate.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_liveupdate.c b/drivers/vfio/pci/vfio_pci_liveupdate.c
index 8e0ee01127b3..789b52665e35 100644
--- a/drivers/vfio/pci/vfio_pci_liveupdate.c
+++ b/drivers/vfio/pci/vfio_pci_liveupdate.c
@@ -54,6 +54,7 @@ static int vfio_pci_liveupdate_prepare(struct liveupdate_file_handler *handler,
 		goto err_free_folio;
 
 	*data = virt_to_phys(ser);
+	vdev->pdev->skip_kexec_clear_master = true;
 
 	return 0;
 
@@ -67,7 +68,12 @@ static void vfio_pci_liveupdate_cancel(struct liveupdate_file_handler *handler,
 {
 	struct vfio_pci_core_device_ser *ser = phys_to_virt(data);
 	struct folio *folio = virt_to_folio(ser);
+	struct vfio_pci_core_device *vdev;
+	struct vfio_device *device;
 
+	device = vfio_device_from_file(file);
+	vdev = container_of(device, struct vfio_pci_core_device, vdev);
+	vdev->pdev->skip_kexec_clear_master = false;
 	WARN_ON_ONCE(kho_unpreserve_folio(folio));
 	folio_put(folio);
 }
-- 
2.51.0.858.gf9c4a03a3a-goog