Hi Praan,
On 12/06/2026 20:39, Pranjal Shrivastava wrote:
On Wed, Jun 10, 2026 at 04:43:20PM +0100, Matt Evans wrote:
Previously, vfio_pci_zap_bars() (and the wrapper vfio_pci_zap_and_down_write_memory_lock()) calls were paired with calls to vfio_pci_dma_buf_move().
This commit replaces them with a unified new function, vfio_pci_zap_revoke_bars() containing both the vfio_pci_dma_buf_move() and the unmap_mapping_range(), making it harder for callers to omit one. It adds a wrapper, vfio_pci_lock_zap_revoke_bars(), which takes the write memory_lock before zapping, and adds a new vfio_pci_unrevoke_bars() for the re-enable path.
As of "vfio/pci: Convert BAR mmap() to use a DMABUF", the unmap_mapping_range() to zap is no longer performed for vfio-pci since the DMABUFs used for BAR mappings already zap PTEs when the vfio_pci_dma_buf_move() occurs.
However, it must be assumed that VFIO drivers which override the .mmap op could create mappings _not_ backed by DMABUFs. So, the zap is still performed on revoke if .mmap is overridden, using a new zap_bars_on_revoke flag. A driver can explicitly opt out; the flag is cleared by the hisi_acc_vfio_pci driver, since its .mmap just wraps vfio_pci_core_mmap() and so still uses DMABUFs.
Signed-off-by: Matt Evans matt@ozlabs.org
.../vfio/pci/hisilicon/hisi_acc_vfio_pci.c | 8 +++ drivers/vfio/pci/vfio_pci_config.c | 30 ++++---- drivers/vfio/pci/vfio_pci_core.c | 70 +++++++++++++------ drivers/vfio/pci/vfio_pci_priv.h | 3 +- include/linux/vfio_pci_core.h | 1 + 5 files changed, 73 insertions(+), 39 deletions(-)
diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c index 86362ec424a5..51990f6d66d5 100644 --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c @@ -1692,6 +1692,14 @@ static int hisi_acc_vfio_pci_probe(struct pci_dev *pdev, const struct pci_device if (ret) goto out_put_vdev;
- /*
* hisi_acc_vfio_pci_mmap() calls down to* vfio_pci_core_mmap(), so BAR mappings are still* DMABUF-backed. They don't require a zap on revoke, so opt* out:*/- hisi_acc_vdev->core_device.zap_bars_on_revoke = false;
This seems to be happening after we vfio_pci_core_register_device, which could be slightly problematic if another device in the same group races to trigger a hot reset before we can set this to false. Could we initialize this flag before registration instead?
Remember it is a safe default, so in the event of a driver not managing to opt-out before it's required then all that happens is a redundant unmap_mapping_range(). The default-safe was a nice suggestion from Alex on v2.
Matt