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Subject[PATCH AUTOSEL 4.19 125/191] vfio/pci: Mask buggy SR-IOV VF INTx support
Date
From: Alex Williamson <alex.williamson@redhat.com>

[ Upstream commit db04264fe9bc0f2b62e036629f9afb530324b693 ]

The SR-IOV spec requires that VFs must report zero for the INTx pin
register as VFs are precluded from INTx support. It's much easier for
the host kernel to understand whether a device is a VF and therefore
whether a non-zero pin register value is bogus than it is to do the
same in userspace. Override the INTx count for such devices and
virtualize the pin register to provide a consistent view of the device
to the user.

As this is clearly a spec violation, warn about it to support hardware
validation, but also provide a known whitelist as it doesn't do much
good to continue complaining if the hardware vendor doesn't plan to
fix it.

Known devices with this issue: 8086:270c

Tested-by: Gage Eads <gage.eads@intel.com>
Reviewed-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/vfio/pci/vfio_pci.c | 8 ++++++--
drivers/vfio/pci/vfio_pci_config.c | 27 +++++++++++++++++++++++++++
2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index a92c2868d9021..0a6eb53e79fbf 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -443,10 +443,14 @@ static int vfio_pci_get_irq_count(struct vfio_pci_device *vdev, int irq_type)
{
if (irq_type == VFIO_PCI_INTX_IRQ_INDEX) {
u8 pin;
+
+ if (!IS_ENABLED(CONFIG_VFIO_PCI_INTX) ||
+ vdev->nointx || vdev->pdev->is_virtfn)
+ return 0;
+
pci_read_config_byte(vdev->pdev, PCI_INTERRUPT_PIN, &pin);
- if (IS_ENABLED(CONFIG_VFIO_PCI_INTX) && !vdev->nointx && pin)
- return 1;

+ return pin ? 1 : 0;
} else if (irq_type == VFIO_PCI_MSI_IRQ_INDEX) {
u8 pos;
u16 flags;
diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index 62023b4a373b4..423ea1f98441a 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -1611,6 +1611,15 @@ static int vfio_ecap_init(struct vfio_pci_device *vdev)
return 0;
}

+/*
+ * Nag about hardware bugs, hopefully to have vendors fix them, but at least
+ * to collect a list of dependencies for the VF INTx pin quirk below.
+ */
+static const struct pci_device_id known_bogus_vf_intx_pin[] = {
+ { PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0x270c) },
+ {}
+};
+
/*
* For each device we allocate a pci_config_map that indicates the
* capability occupying each dword and thus the struct perm_bits we
@@ -1676,6 +1685,24 @@ int vfio_config_init(struct vfio_pci_device *vdev)
if (pdev->is_virtfn) {
*(__le16 *)&vconfig[PCI_VENDOR_ID] = cpu_to_le16(pdev->vendor);
*(__le16 *)&vconfig[PCI_DEVICE_ID] = cpu_to_le16(pdev->device);
+
+ /*
+ * Per SR-IOV spec rev 1.1, 3.4.1.18 the interrupt pin register
+ * does not apply to VFs and VFs must implement this register
+ * as read-only with value zero. Userspace is not readily able
+ * to identify whether a device is a VF and thus that the pin
+ * definition on the device is bogus should it violate this
+ * requirement. We already virtualize the pin register for
+ * other purposes, so we simply need to replace the bogus value
+ * and consider VFs when we determine INTx IRQ count.
+ */
+ if (vconfig[PCI_INTERRUPT_PIN] &&
+ !pci_match_id(known_bogus_vf_intx_pin, pdev))
+ pci_warn(pdev,
+ "Hardware bug: VF reports bogus INTx pin %d\n",
+ vconfig[PCI_INTERRUPT_PIN]);
+
+ vconfig[PCI_INTERRUPT_PIN] = 0; /* Gratuitous for good VFs */
}

if (!IS_ENABLED(CONFIG_VFIO_PCI_INTX) || vdev->nointx)
--
2.20.1
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