Commit 7302327a authored by Leo Yan's avatar Leo Yan Committed by Will Deacon
Browse files

vfio-pci: Re-enable INTx mode when disable MSI/MSIX



Since PCI forbids enabling INTx, MSI or MSIX at the same time, it's by
default to disable INTx mode when enable MSI/MSIX mode; but this logic is
easily broken if the guest PCI driver detects the MSI/MSIX cannot work as
expected and tries to rollback to use INTx mode.  In this case, the INTx
mode has been disabled and has no chance to re-enable it, thus both INTx
mode and MSI/MSIX mode cannot work in vfio.

Below shows the detailed flow for introducing this issue:

  vfio_pci_configure_dev_irqs()
    `-> vfio_pci_enable_intx()

  vfio_pci_enable_msis()
    `-> vfio_pci_disable_intx()

  vfio_pci_disable_msis()   => Guest PCI driver disables MSI

To fix this issue, when disable MSI/MSIX we need to check if INTx mode
is available for this device or not; if the device can support INTx then
re-enable it so that the device can fallback to use it.

Since vfio_pci_disable_intx() / vfio_pci_enable_intx() pair functions
may be called for multiple times, this patch uses 'intx_fd == -1' to
denote the INTx is disabled, the pair functions can directly bail out
when detect INTx has been disabled and enabled respectively.
Suggested-by: default avatarJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Leo Yan's avatarLeo Yan <leo.yan@linaro.org>
Reviewed-by: default avatarJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 12bd7a16
......@@ -28,6 +28,7 @@ struct vfio_irq_eventfd {
msi_update_state(state, val, VFIO_PCI_MSI_STATE_EMPTY)
static void vfio_pci_disable_intx(struct kvm *kvm, struct vfio_device *vdev);
static int vfio_pci_enable_intx(struct kvm *kvm, struct vfio_device *vdev);
static int vfio_pci_enable_msis(struct kvm *kvm, struct vfio_device *vdev,
bool msix)
......@@ -50,17 +51,14 @@ static int vfio_pci_enable_msis(struct kvm *kvm, struct vfio_device *vdev,
if (!msi_is_enabled(msis->virt_state))
return 0;
if (pdev->irq_modes & VFIO_PCI_IRQ_MODE_INTX) {
if (pdev->irq_modes & VFIO_PCI_IRQ_MODE_INTX)
/*
* PCI (and VFIO) forbids enabling INTx, MSI or MSIX at the same
* time. Since INTx has to be enabled from the start (we don't
* have a reliable way to know when the user starts using it),
* have a reliable way to know when the guest starts using it),
* disable it now.
*/
vfio_pci_disable_intx(kvm, vdev);
/* Permanently disable INTx */
pdev->irq_modes &= ~VFIO_PCI_IRQ_MODE_INTX;
}
eventfds = (void *)msis->irq_set + sizeof(struct vfio_irq_set);
......@@ -162,7 +160,16 @@ static int vfio_pci_disable_msis(struct kvm *kvm, struct vfio_device *vdev,
msi_set_enabled(msis->phys_state, false);
msi_set_empty(msis->phys_state, true);
return 0;
/*
* When MSI or MSIX is disabled, this might be called when
* PCI driver detects the MSI interrupt failure and wants to
* rollback to INTx mode. Thus enable INTx if the device
* supports INTx mode in this case.
*/
if (pdev->irq_modes & VFIO_PCI_IRQ_MODE_INTX)
ret = vfio_pci_enable_intx(kvm, vdev);
return ret >= 0 ? 0 : ret;
}
static int vfio_pci_update_msi_entry(struct kvm *kvm, struct vfio_device *vdev,
......@@ -1002,6 +1009,9 @@ static void vfio_pci_disable_intx(struct kvm *kvm, struct vfio_device *vdev)
.index = VFIO_PCI_INTX_IRQ_INDEX,
};
if (pdev->intx_fd == -1)
return;
pr_debug("user requested MSI, disabling INTx %d", gsi);
ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, &irq_set);
......@@ -1009,6 +1019,7 @@ static void vfio_pci_disable_intx(struct kvm *kvm, struct vfio_device *vdev)
close(pdev->intx_fd);
close(pdev->unmask_fd);
pdev->intx_fd = -1;
}
static int vfio_pci_enable_intx(struct kvm *kvm, struct vfio_device *vdev)
......@@ -1020,6 +1031,9 @@ static int vfio_pci_enable_intx(struct kvm *kvm, struct vfio_device *vdev)
struct vfio_pci_device *pdev = &vdev->pci;
int gsi = pdev->intx_gsi;
if (pdev->intx_fd != -1)
return 0;
/*
* PCI IRQ is level-triggered, so we use two eventfds. trigger_fd
* signals an interrupt from host to guest, and unmask_fd signals the
......@@ -1122,6 +1136,8 @@ static int vfio_pci_init_intx(struct kvm *kvm, struct vfio_device *vdev)
/* Guest is going to ovewrite our irq_line... */
pdev->intx_gsi = pdev->hdr.irq_line - KVM_IRQ_OFFSET;
pdev->intx_fd = -1;
return 0;
}
......
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