From: Robin Murphy <robin.murphy@arm.com>
To: Wei Liu <wei.liu@kernel.org>,
Linux on Hyper-V List <linux-hyperv@vger.kernel.org>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
pasha.tatashin@soleen.com, kumarpraveen@linux.microsoft.com,
Will Deacon <will@kernel.org>,
Haiyang Zhang <haiyangz@microsoft.com>,
Dexuan Cui <decui@microsoft.com>,
Linux Kernel List <linux-kernel@vger.kernel.org>,
Michael Kelley <mikelley@microsoft.com>,
"open list:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>,
Nuno Das Neves <nunodasneves@linux.microsoft.com>,
Sunil Muthuswamy <sunilmut@microsoft.com>,
virtualization@lists.linux-foundation.org,
Vineeth Pillai <viremana@linux.microsoft.com>
Subject: Re: [RFC v1 6/8] mshv: command line option to skip devices in PV-IOMMU
Date: Fri, 9 Jul 2021 13:46:19 +0100 [thread overview]
Message-ID: <1c839a00-0f5f-fdfa-cfb3-f345bef9f849@arm.com> (raw)
In-Reply-To: <20210709114339.3467637-7-wei.liu@kernel.org>
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@kernel.org>
> ---
> 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);
>
next prev parent reply other threads:[~2021-07-09 12:46 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-09 11:43 [RFC v1 0/8] MSHV: add PV-IOMMU driver Wei Liu
2021-07-09 11:43 ` [RFC v1 1/8] x86/hyperv: export hv_build_pci_dev_id Wei Liu
2021-07-09 11:43 ` [RFC v1 2/8] asm-generic/hyperv: add device domain definitions Wei Liu
2021-07-09 11:43 ` [RFC v1 3/8] intel/vt-d: make DMAR table parsing code more flexible Wei Liu
2021-07-09 12:56 ` Robin Murphy
2021-07-09 13:42 ` Wei Liu
2021-07-09 11:43 ` [RFC v1 4/8] intel/vt-d: export intel_iommu_get_resv_regions Wei Liu
2021-07-09 14:17 ` Lu Baolu
2021-07-09 14:21 ` Wei Liu
2021-07-09 11:43 ` [RFC v1 5/8] mshv: add paravirtualized IOMMU support Wei Liu
2021-08-03 18:40 ` Praveen Kumar
2021-08-03 21:47 ` Wei Liu
2021-08-04 6:43 ` Praveen Kumar
2021-08-10 10:46 ` Wei Liu
2021-07-09 11:43 ` [RFC v1 6/8] mshv: command line option to skip devices in PV-IOMMU Wei Liu
2021-07-09 12:46 ` Robin Murphy [this message]
2021-07-09 13:34 ` Wei Liu
2021-08-03 18:50 ` Praveen Kumar
2021-08-03 21:56 ` Wei Liu
2021-08-04 7:03 ` Praveen Kumar
2021-08-10 10:04 ` Wei Liu
2021-07-09 11:43 ` [RFC v1 7/8] mshv: implement in-kernel device framework Wei Liu
2021-07-09 13:02 ` Matthew Wilcox
2021-07-09 13:50 ` Wei Liu
2021-07-09 15:32 ` Matthew Wilcox
2021-07-09 16:27 ` Wei Liu
2021-07-09 16:38 ` Matthew Wilcox
2021-07-09 19:14 ` Wei Liu
2021-07-09 19:48 ` Matthew Wilcox
2021-07-09 20:11 ` Wei Liu
2021-08-03 19:12 ` Praveen Kumar
2021-08-03 22:04 ` Wei Liu
2021-07-09 11:43 ` [RFC v1 8/8] mshv: add vfio bridge device Wei Liu
2021-08-03 19:27 ` Praveen Kumar
2021-08-10 10:52 ` Wei Liu
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