From b0223e29afdc88cc262a764026296414396cd129 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Tue, 8 Jan 2013 14:09:03 -0700 Subject: [PATCH 1/2] vfio-pci: Make host MSI-X enable track guest Guests typically enable MSI-X with all of the vectors in the MSI-X vector table masked. Only when the vector is enabled does the vector get unmasked, resulting in a vector_use callback. These two points, enable and unmask, correspond to pci_enable_msix() and request_irq() for Linux guests. Some drivers rely on VF/PF or PF/fw communication channels that expect the physical state of the device to match the guest visible state of the device. They don't appreciate lazily enabling MSI-X on the physical device. To solve this, enable MSI-X with a single vector when the MSI-X capability is enabled and immediate disable the vector. This leaves the physical device in exactly the same state between host and guest. Furthermore, the brief gap where we enable vector 0, it fires into userspace, not KVM, so the guest doesn't get spurious interrupts. Ideally we could call VFIO_DEVICE_SET_IRQS with the right parameters to enable MSI-X with zero vectors, but this will currently return an error as the Linux MSI-X interfaces do not allow it. Signed-off-by: Alex Williamson Cc: qemu-stable@nongnu.org --- hw/vfio_pci.c | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) diff --git a/hw/vfio_pci.c b/hw/vfio_pci.c index 28c83031d0f3..8ec1faf27e13 100644 --- a/hw/vfio_pci.c +++ b/hw/vfio_pci.c @@ -562,8 +562,8 @@ static int vfio_enable_vectors(VFIODevice *vdev, bool msix) return ret; } -static int vfio_msix_vector_use(PCIDevice *pdev, - unsigned int nr, MSIMessage msg) +static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr, + MSIMessage *msg, IOHandler *handler) { VFIODevice *vdev = DO_UPCAST(VFIODevice, pdev, pdev); VFIOMSIVector *vector; @@ -587,7 +587,7 @@ static int vfio_msix_vector_use(PCIDevice *pdev, * Attempt to enable route through KVM irqchip, * default to userspace handling if unavailable. */ - vector->virq = kvm_irqchip_add_msi_route(kvm_state, msg); + vector->virq = msg ? kvm_irqchip_add_msi_route(kvm_state, *msg) : -1; if (vector->virq < 0 || kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->interrupt, vector->virq) < 0) { @@ -596,7 +596,7 @@ static int vfio_msix_vector_use(PCIDevice *pdev, vector->virq = -1; } qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt), - vfio_msi_interrupt, NULL, vector); + handler, NULL, vector); } /* @@ -639,6 +639,12 @@ static int vfio_msix_vector_use(PCIDevice *pdev, return 0; } +static int vfio_msix_vector_use(PCIDevice *pdev, + unsigned int nr, MSIMessage msg) +{ + return vfio_msix_vector_do_use(pdev, nr, &msg, vfio_msi_interrupt); +} + static void vfio_msix_vector_release(PCIDevice *pdev, unsigned int nr) { VFIODevice *vdev = DO_UPCAST(VFIODevice, pdev, pdev); @@ -697,6 +703,22 @@ static void vfio_enable_msix(VFIODevice *vdev) vdev->interrupt = VFIO_INT_MSIX; + /* + * Some communication channels between VF & PF or PF & fw rely on the + * physical state of the device and expect that enabling MSI-X from the + * guest enables the same on the host. When our guest is Linux, the + * guest driver call to pci_enable_msix() sets the enabling bit in the + * MSI-X capability, but leaves the vector table masked. We therefore + * can't rely on a vector_use callback (from request_irq() in the guest) + * to switch the physical device into MSI-X mode because that may come a + * long time after pci_enable_msix(). This code enables vector 0 with + * triggering to userspace, then immediately release the vector, leaving + * the physical device with no vectors enabled, but MSI-X enabled, just + * like the guest view. + */ + vfio_msix_vector_do_use(&vdev->pdev, 0, NULL, NULL); + vfio_msix_vector_release(&vdev->pdev, 0); + if (msix_set_vector_notifiers(&vdev->pdev, vfio_msix_vector_use, vfio_msix_vector_release, NULL)) { error_report("vfio: msix_set_vector_notifiers failed\n"); From 8fc94e5a8046e349e07976f9bcaffbcd5833f3a2 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Tue, 8 Jan 2013 14:10:03 -0700 Subject: [PATCH 2/2] vfio-pci: Loosen sanity checks to allow future features VFIO_PCI_NUM_REGIONS and VFIO_PCI_NUM_IRQS should never have been used in this manner as it locks a specific kernel implementation. Future features may introduce new regions or interrupt entries (VGA may add legacy ranges, AER might add an IRQ for error signalling). Fix this before it gets us into trouble. Signed-off-by: Alex Williamson Cc: qemu-stable@nongnu.org --- hw/vfio_pci.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/hw/vfio_pci.c b/hw/vfio_pci.c index 8ec1faf27e13..c51ae6761b7b 100644 --- a/hw/vfio_pci.c +++ b/hw/vfio_pci.c @@ -1837,13 +1837,13 @@ static int vfio_get_device(VFIOGroup *group, const char *name, VFIODevice *vdev) error_report("Warning, device %s does not support reset\n", name); } - if (dev_info.num_regions != VFIO_PCI_NUM_REGIONS) { + if (dev_info.num_regions < VFIO_PCI_CONFIG_REGION_INDEX + 1) { error_report("vfio: unexpected number of io regions %u\n", dev_info.num_regions); goto error; } - if (dev_info.num_irqs != VFIO_PCI_NUM_IRQS) { + if (dev_info.num_irqs < VFIO_PCI_MSIX_IRQ_INDEX + 1) { error_report("vfio: unexpected number of irqs %u\n", dev_info.num_irqs); goto error; }