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From: Praveen Kumar <kumarpraveen@linux.microsoft.com>
To: Wei Liu <wei.liu@kernel.org>,
	Linux on Hyper-V List <linux-hyperv@vger.kernel.org>
Cc: virtualization@lists.linux-foundation.org,
	Linux Kernel List <linux-kernel@vger.kernel.org>,
	Michael Kelley <mikelley@microsoft.com>,
	Vineeth Pillai <viremana@linux.microsoft.com>,
	Sunil Muthuswamy <sunilmut@microsoft.com>,
	Nuno Das Neves <nunodasneves@linux.microsoft.com>,
	pasha.tatashin@soleen.com, "K. Y. Srinivasan" <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Dexuan Cui <decui@microsoft.com>, Joerg Roedel <joro@8bytes.org>,
	Will Deacon <will@kernel.org>,
	"open list:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>
Subject: Re: [RFC v1 6/8] mshv: command line option to skip devices in PV-IOMMU
Date: Wed, 4 Aug 2021 00:20:42 +0530	[thread overview]
Message-ID: <4a6918ea-e3e5-55c9-a12d-bee7261301fd@linux.microsoft.com> (raw)
In-Reply-To: <20210709114339.3467637-7-wei.liu@kernel.org>

On 09-07-2021 17:13, 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.
> 
> 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]);

Is there a possibility of pci_devs_to_skip + pos > sizeof(pci_devs_to_skip) and also a valid memory ?
I would recommend to have a check of size as well before accessing the array content, just to be safer accessing any memory.

> +	}
> +
>  	vdev = kzalloc(sizeof(*vdev), GFP_KERNEL);
>  	if (!vdev)
>  		return ERR_PTR(-ENOMEM);
> 

Regards,

~Praveen.

  parent reply	other threads:[~2021-08-03 18:50 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
2021-07-09 13:34     ` Wei Liu
2021-08-03 18:50   ` Praveen Kumar [this message]
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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