diff options
author | Leo Yan <leo.yan@linaro.org> | 2019-04-08 09:27:19 +0800 |
---|---|---|
committer | Will Deacon <will.deacon@arm.com> | 2019-04-26 14:49:11 +0100 |
commit | 7302327a491c6fd3613d5903c0310dd6abb1a74e (patch) | |
tree | 4dc158ae33a809d0e0f897cf5e4637a64beec225 | |
parent | 12bd7a16811bc250fee97f106a874720abd2346d (diff) | |
download | kvmtool-7302327a491c6fd3613d5903c0310dd6abb1a74e.tar.gz |
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: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Reviewed-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
-rw-r--r-- | vfio/pci.c | 28 |
1 files changed, 22 insertions, 6 deletions
@@ -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; } |