On 2021-07-09 12:43, Wei Liu wrote:
Some devices may have been claimed by the hypervisor already. One such example is a user can assign a NIC for debugging purpose. Ideally Linux should be able to tell retrieve that information, but there is no way to do that yet. And designing that new mechanism is going to take time. Provide a command line option for skipping devices. This is a stopgap solution, so it is intentionally undocumented. Hopefully we can retire it in the future.
Huh? If the host is using a device, why the heck is it exposing any knowledge of that device to the guest at all, let alone allowing the guest to do anything that could affect its operation!?
Robin.
Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx> --- drivers/iommu/hyperv-iommu.c | 45 ++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c index 043dcff06511..353da5036387 100644 --- a/drivers/iommu/hyperv-iommu.c +++ b/drivers/iommu/hyperv-iommu.c @@ -349,6 +349,16 @@ static const struct irq_domain_ops hyperv_root_ir_domain_ops = {#ifdef CONFIG_HYPERV_ROOT_PVIOMMU +/* The IOMMU will not claim these PCI devices. */+static char *pci_devs_to_skip; +static int __init mshv_iommu_setup_skip(char *str) { + pci_devs_to_skip = str; + + return 0; +} +/* mshv_iommu_skip=(SSSS:BB:DD.F)(SSSS:BB:DD.F) */ +__setup("mshv_iommu_skip=", mshv_iommu_setup_skip); + /* DMA remapping support */ struct hv_iommu_domain { struct iommu_domain domain; @@ -774,6 +784,41 @@ static struct iommu_device *hv_iommu_probe_device(struct device *dev) if (!dev_is_pci(dev)) return ERR_PTR(-ENODEV);+ /*+ * Skip the PCI device specified in `pci_devs_to_skip`. This is a + * temporary solution until we figure out a way to extract information + * from the hypervisor what devices it is already using. + */ + if (pci_devs_to_skip && *pci_devs_to_skip) { + int pos = 0; + int parsed; + int segment, bus, slot, func; + struct pci_dev *pdev = to_pci_dev(dev); + + do { + parsed = 0; + + sscanf(pci_devs_to_skip + pos, + " (%x:%x:%x.%x) %n", + &segment, &bus, &slot, &func, &parsed); + + if (parsed <= 0) + break; + + if (pci_domain_nr(pdev->bus) == segment && + pdev->bus->number == bus && + PCI_SLOT(pdev->devfn) == slot && + PCI_FUNC(pdev->devfn) == func) + { + dev_info(dev, "skipped by MSHV IOMMU\n"); + return ERR_PTR(-ENODEV); + } + + pos += parsed; + + } while (pci_devs_to_skip[pos]); + } + vdev = kzalloc(sizeof(*vdev), GFP_KERNEL); if (!vdev) return ERR_PTR(-ENOMEM);
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