[PATCH v4 3/3] vfio/pci: Decouple MSE bit checks from is_virtfn

Matthew Rosato
2020-09-02T19:47:27Z

While it is true that devices with is_virtfn=1 will have an
MSE that is hard-wired to 0, this is not the only case where
we see this behavior -- For example some bare-metal hypervisors
lack MSE bit emulation for devices not setting is_virtfn (s390).
Fix this by instead checking for the newly-added
PCI_DEV_FLAGS_FORCE_COMMAND_MEM flag which directly denotes the
need for MSE bit emulation in vfio.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
---
drivers/vfio/pci/vfio_pci_config.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index d98843f..47fb3c7 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -406,7 +406,8 @@ bool __vfio_pci_memory_enabled(struct vfio_pci_device *vdev)
* PF SR-IOV capability, there's therefore no need to trigger
* faults based on the virtual value.
*/
- return pdev->is_virtfn || (cmd & PCI_COMMAND_MEMORY);
+ return (pdev->dev_flags & PCI_DEV_FLAGS_FORCE_COMMAND_MEM) ||
+ (cmd & PCI_COMMAND_MEMORY);
}

/*
@@ -520,8 +521,9 @@ static int vfio_basic_config_read(struct vfio_pci_device *vdev, int pos,

count = vfio_default_config_read(vdev, pos, count, perm, offset, val);

- /* Mask in virtual memory enable for SR-IOV devices */
- if (offset == PCI_COMMAND && vdev->pdev->is_virtfn) {
+ /* Mask in virtual memory enable */
+ if ((offset == PCI_COMMAND) &&
+ (vdev->pdev->dev_flags & PCI_DEV_FLAGS_FORCE_COMMAND_MEM)) {
u16 cmd = le16_to_cpu(*(__le16 *)&vdev->vconfig[PCI_COMMAND]);
u32 tmp_val = le32_to_cpu(*val);

@@ -589,9 +591,11 @@ static int vfio_basic_config_write(struct vfio_pci_device *vdev, int pos,
* shows it disabled (phys_mem/io, then the device has
* undergone some kind of backdoor reset and needs to be
* restored before we allow it to enable the bars.
- * SR-IOV devices will trigger this, but we catch them later
+ * SR-IOV devices will trigger this - for mem enable let's
+ * catch this now and for io enable it will be caught later
*/
- if ((new_mem && virt_mem && !phys_mem) ||
+ if ((new_mem && virt_mem && !phys_mem &&
+ !(pdev->dev_flags & PCI_DEV_FLAGS_FORCE_COMMAND_MEM)) ||
(new_io && virt_io && !phys_io) ||
vfio_need_bar_restore(vdev))
vfio_bar_restore(vdev);
@@ -1734,9 +1738,11 @@ int vfio_config_init(struct vfio_pci_device *vdev)
vconfig[PCI_INTERRUPT_PIN]);

vconfig[PCI_INTERRUPT_PIN] = 0; /* Gratuitous for good VFs */
-
+ }
+ if (pdev->dev_flags & PCI_DEV_FLAGS_FORCE_COMMAND_MEM) {
/*
- * VFs do no implement the memory enable bit of the COMMAND
+ * VFs and devices that set PCI_DEV_FLAGS_FORCE_COMMAND_MEM
+ * do not implement the memory enable bit of the COMMAND
* register therefore we'll not have it set in our initial
* copy of config space after pci_enable_device(). For
* consistency with PFs, set the virtual enable bit here.
--
1.8.3.1