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From: Wei Liu <wei.liu@kernel.org>
To: Praveen Kumar <kumarpraveen@linux.microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>,
	Linux on Hyper-V List <linux-hyperv@vger.kernel.org>,
	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, Joerg Roedel <joro@8bytes.org>,
	Will Deacon <will@kernel.org>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Dexuan Cui <decui@microsoft.com>,
	"open list:IOMMU DRIVERS" <iommu@lists.linux-foundation.org>
Subject: Re: [RFC v1 5/8] mshv: add paravirtualized IOMMU support
Date: Tue, 3 Aug 2021 21:47:18 +0000	[thread overview]
Message-ID: <20210803214718.hnp3ejs35lh455fw@liuwe-devbox-debian-v2> (raw)
In-Reply-To: <77670985-2a1b-7bbd-2ede-4b7810c3e220@linux.microsoft.com>

On Wed, Aug 04, 2021 at 12:10:45AM +0530, Praveen Kumar wrote:
> On 09-07-2021 17:13, Wei Liu wrote:
> > +static void hv_iommu_domain_free(struct iommu_domain *d)
> > +{
> > +	struct hv_iommu_domain *domain = to_hv_iommu_domain(d);
> > +	unsigned long flags;
> > +	u64 status;
> > +	struct hv_input_delete_device_domain *input;
> > +
> > +	if (is_identity_domain(domain) || is_null_domain(domain))
> > +		return;
> > +
> > +	local_irq_save(flags);
> > +	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> > +	memset(input, 0, sizeof(*input));
> > +
> > +	input->device_domain= domain->device_domain;
> > +
> > +	status = hv_do_hypercall(HVCALL_DELETE_DEVICE_DOMAIN, input, NULL);
> > +
> > +	local_irq_restore(flags);
> > +
> > +	if (!hv_result_success(status))
> > +		pr_err("%s: hypercall failed, status %lld\n", __func__, status);
> 
> Is it OK to deallocate the resources, if hypercall has failed ?

It should be fine. We leak some resources in the hypervisor, but Linux
is in a rather wedged state anyway. Refusing to free up resources in
Linux does not much good.

> Do we have any specific error code EBUSY (kind of) which we need to wait upon ?
> 

I have not found a circumstance that can happen.

> > +
> > +	ida_free(&domain->hv_iommu->domain_ids, domain->device_domain.domain_id.id);
> > +
> > +	iommu_put_dma_cookie(d);
> > +
> > +	kfree(domain);
> > +}
> > +
> > +static int hv_iommu_attach_dev(struct iommu_domain *d, struct device *dev)
> > +{
> > +	struct hv_iommu_domain *domain = to_hv_iommu_domain(d);
> > +	u64 status;
> > +	unsigned long flags;
> > +	struct hv_input_attach_device_domain *input;
> > +	struct pci_dev *pdev;
> > +	struct hv_iommu_endpoint *vdev = dev_iommu_priv_get(dev);
> > +
> > +	/* Only allow PCI devices for now */
> > +	if (!dev_is_pci(dev))
> > +		return -EINVAL;
> > +
> > +	pdev = to_pci_dev(dev);
> > +
> > +	dev_dbg(dev, "Attaching (%strusted) to %d\n", pdev->untrusted ? "un" : "",
> > +		domain->device_domain.domain_id.id);
> > +
> > +	local_irq_save(flags);
> > +	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> > +	memset(input, 0, sizeof(*input));
> > +
> > +	input->device_domain = domain->device_domain;
> > +	input->device_id = hv_build_pci_dev_id(pdev);
> > +
> > +	status = hv_do_hypercall(HVCALL_ATTACH_DEVICE_DOMAIN, input, NULL);
> > +	local_irq_restore(flags);
> > +
> > +	if (!hv_result_success(status))
> > +		pr_err("%s: hypercall failed, status %lld\n", __func__, status);
> 
> Does it make sense to vdev->domain = NULL ?
>

It is already NULL -- there is no other code path that sets it and the
detach path always sets the field to NULL.

> > +	else
> > +		vdev->domain = domain;
> > +
> > +	return hv_status_to_errno(status);
> > +}
> > +
[...]
> > +static size_t hv_iommu_unmap(struct iommu_domain *d, unsigned long iova,
> > +			   size_t size, struct iommu_iotlb_gather *gather)
> > +{
> > +	size_t unmapped;
> > +	struct hv_iommu_domain *domain = to_hv_iommu_domain(d);
> > +	unsigned long flags, npages;
> > +	struct hv_input_unmap_device_gpa_pages *input;
> > +	u64 status;
> > +
> > +	unmapped = hv_iommu_del_mappings(domain, iova, size);
> > +	if (unmapped < size)
> > +		return 0;
> 
> Is there a case where unmapped > 0 && unmapped < size ?
> 

There could be such a case -- hv_iommu_del_mappings' return value is >= 0.
Is there a problem with this predicate?

Wei.

  reply	other threads:[~2021-08-03 21:47 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 [this message]
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
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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