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-rw-r--r--drivers/vfio/pci/vfio_pci_config.c29
1 files changed, 26 insertions, 3 deletions
diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index 91335e6de88a..115a36f6f403 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -808,6 +808,7 @@ static int vfio_exp_config_write(struct vfio_pci_device *vdev, int pos,
{
__le16 *ctrl = (__le16 *)(vdev->vconfig + pos -
offset + PCI_EXP_DEVCTL);
+ int readrq = le16_to_cpu(*ctrl) & PCI_EXP_DEVCTL_READRQ;
count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
if (count < 0)
@@ -833,6 +834,27 @@ static int vfio_exp_config_write(struct vfio_pci_device *vdev, int pos,
pci_try_reset_function(vdev->pdev);
}
+ /*
+ * MPS is virtualized to the user, writes do not change the physical
+ * register since determining a proper MPS value requires a system wide
+ * device view. The MRRS is largely independent of MPS, but since the
+ * user does not have that system-wide view, they might set a safe, but
+ * inefficiently low value. Here we allow writes through to hardware,
+ * but we set the floor to the physical device MPS setting, so that
+ * we can at least use full TLPs, as defined by the MPS value.
+ *
+ * NB, if any devices actually depend on an artificially low MRRS
+ * setting, this will need to be revisited, perhaps with a quirk
+ * though pcie_set_readrq().
+ */
+ if (readrq != (le16_to_cpu(*ctrl) & PCI_EXP_DEVCTL_READRQ)) {
+ readrq = 128 <<
+ ((le16_to_cpu(*ctrl) & PCI_EXP_DEVCTL_READRQ) >> 12);
+ readrq = max(readrq, pcie_get_mps(vdev->pdev));
+
+ pcie_set_readrq(vdev->pdev, readrq);
+ }
+
return count;
}
@@ -851,11 +873,12 @@ static int __init init_pci_cap_exp_perm(struct perm_bits *perm)
* Allow writes to device control fields, except devctl_phantom,
* which could confuse IOMMU, MPS, which can break communication
* with other physical devices, and the ARI bit in devctl2, which
- * is set at probe time. FLR gets virtualized via our writefn.
+ * is set at probe time. FLR and MRRS get virtualized via our
+ * writefn.
*/
p_setw(perm, PCI_EXP_DEVCTL,
- PCI_EXP_DEVCTL_BCR_FLR | PCI_EXP_DEVCTL_PAYLOAD,
- ~PCI_EXP_DEVCTL_PHANTOM);
+ PCI_EXP_DEVCTL_BCR_FLR | PCI_EXP_DEVCTL_PAYLOAD |
+ PCI_EXP_DEVCTL_READRQ, ~PCI_EXP_DEVCTL_PHANTOM);
p_setw(perm, PCI_EXP_DEVCTL2, NO_VIRT, ~PCI_EXP_DEVCTL2_ARI);
return 0;
}