From b27bbf1f5b9e62b7b0b8ce9a4f5e474c3119a9a9 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Mon, 2 Oct 2017 12:39:09 -0600 Subject: [PATCH] vfio/pci: Virtualize Maximum Payload Size [ Upstream commit 523184972b282cd9ca17a76f6ca4742394856818 ] With virtual PCI-Express chipsets, we now see userspace/guest drivers trying to match the physical MPS setting to a virtual downstream port. Of course a lone physical device surrounded by virtual interconnects cannot make a correct decision for a proper MPS setting. Instead, let's virtualize the MPS control register so that writes through to hardware are disallowed. Userspace drivers like QEMU assume they can write anything to the device and we'll filter out anything dangerous. Since mismatched MPS can lead to AER and other faults, let's add it to the kernel side rather than relying on userspace virtualization to handle it. Signed-off-by: Alex Williamson Reviewed-by: Eric Auger Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/vfio/pci/vfio_pci_config.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c index 5628fe114347..91335e6de88a 100644 --- a/drivers/vfio/pci/vfio_pci_config.c +++ b/drivers/vfio/pci/vfio_pci_config.c @@ -849,11 +849,13 @@ 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, and the ARI bit in devctl2, which + * 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. */ p_setw(perm, PCI_EXP_DEVCTL, - PCI_EXP_DEVCTL_BCR_FLR, ~PCI_EXP_DEVCTL_PHANTOM); + PCI_EXP_DEVCTL_BCR_FLR | PCI_EXP_DEVCTL_PAYLOAD, + ~PCI_EXP_DEVCTL_PHANTOM); p_setw(perm, PCI_EXP_DEVCTL2, NO_VIRT, ~PCI_EXP_DEVCTL2_ARI); return 0; } -- 2.11.0