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From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: devicetree@vger.kernel.org, kevin.tian@intel.com, jgg@ziepe.ca,
	linux-pci@vger.kernel.org, robin.murphy@arm.com,
	fenghua.yu@intel.com, hch@infradead.org, linux-mm@kvack.org,
	iommu@lists.linux-foundation.org, zhangfei.gao@linaro.org,
	catalin.marinas@arm.com, felix.kuehling@amd.com, will@kernel.org,
	christian.koenig@amd.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v7 04/24] iommu: Add a page fault handler
Date: Wed, 11 Nov 2020 14:57:40 +0100	[thread overview]
Message-ID: <20201111135740.GA2622074@myrica> (raw)
In-Reply-To: <c840d771-188d-9ee5-d117-e4b91d29b329@linux.intel.com>

Hi Baolu,

Thanks for the review. I'm only now reworking this and realized I've never
sent a reply, sorry about that.

On Wed, May 20, 2020 at 02:42:21PM +0800, Lu Baolu wrote:
> Hi Jean,
> 
> On 2020/5/20 1:54, Jean-Philippe Brucker wrote:
> > Some systems allow devices to handle I/O Page Faults in the core mm. For
> > example systems implementing the PCIe PRI extension or Arm SMMU stall
> > model. Infrastructure for reporting these recoverable page faults was
> > added to the IOMMU core by commit 0c830e6b3282 ("iommu: Introduce device
> > fault report API"). Add a page fault handler for host SVA.
> > 
> > IOMMU driver can now instantiate several fault workqueues and link them
> > to IOPF-capable devices. Drivers can choose between a single global
> > workqueue, one per IOMMU device, one per low-level fault queue, one per
> > domain, etc.
> > 
> > When it receives a fault event, supposedly in an IRQ handler, the IOMMU
> > driver reports the fault using iommu_report_device_fault(), which calls
> > the registered handler. The page fault handler then calls the mm fault
> > handler, and reports either success or failure with iommu_page_response().
> > When the handler succeeded, the IOMMU retries the access.
> > 
> > The iopf_param pointer could be embedded into iommu_fault_param. But
> > putting iopf_param into the iommu_param structure allows us not to care
> > about ordering between calls to iopf_queue_add_device() and
> > iommu_register_device_fault_handler().
> > 
> > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
[...]
> > +static enum iommu_page_response_code
> > +iopf_handle_single(struct iopf_fault *iopf)
> > +{
> > +	vm_fault_t ret;
> > +	struct mm_struct *mm;
> > +	struct vm_area_struct *vma;
> > +	unsigned int access_flags = 0;
> > +	unsigned int fault_flags = FAULT_FLAG_REMOTE;
> > +	struct iommu_fault_page_request *prm = &iopf->fault.prm;
> > +	enum iommu_page_response_code status = IOMMU_PAGE_RESP_INVALID;
> > +
> > +	if (!(prm->flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID))
> > +		return status;
> > +
> > +	mm = iommu_sva_find(prm->pasid);
> > +	if (IS_ERR_OR_NULL(mm))
> > +		return status;
> > +
> > +	down_read(&mm->mmap_sem);
> > +
> > +	vma = find_extend_vma(mm, prm->addr);
> > +	if (!vma)
> > +		/* Unmapped area */
> > +		goto out_put_mm;
> > +
> > +	if (prm->perm & IOMMU_FAULT_PERM_READ)
> > +		access_flags |= VM_READ;
> > +
> > +	if (prm->perm & IOMMU_FAULT_PERM_WRITE) {
> > +		access_flags |= VM_WRITE;
> > +		fault_flags |= FAULT_FLAG_WRITE;
> > +	}
> > +
> > +	if (prm->perm & IOMMU_FAULT_PERM_EXEC) {
> > +		access_flags |= VM_EXEC;
> > +		fault_flags |= FAULT_FLAG_INSTRUCTION;
> > +	}
> > +
> > +	if (!(prm->perm & IOMMU_FAULT_PERM_PRIV))
> > +		fault_flags |= FAULT_FLAG_USER;
> > +
> > +	if (access_flags & ~vma->vm_flags)
> > +		/* Access fault */
> > +		goto out_put_mm;
> > +
> > +	ret = handle_mm_fault(vma, prm->addr, fault_flags);
> > +	status = ret & VM_FAULT_ERROR ? IOMMU_PAGE_RESP_INVALID :
> 
> Do you mind telling why it's IOMMU_PAGE_RESP_INVALID but not
> IOMMU_PAGE_RESP_FAILURE?

PAGE_RESP_FAILURE maps to PRI Response code "Response Failure" which
indicates a catastrophic error and causes the function to disable PRI.
Instead PAGE_RESP_INVALID maps to PRI Response code "Invalid request",
which tells the function that the address is invalid and there is no point
retrying this particular access.

Thanks,
Jean
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  reply	other threads:[~2020-11-11 13:58 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19 17:54 [PATCH v7 00/24] iommu: Shared Virtual Addressing for SMMUv3 Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 01/24] mm: Add a PASID field to mm_struct Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 02/24] iommu/ioasid: Add ioasid references Jean-Philippe Brucker
2020-05-20  2:31   ` Lu Baolu
2020-05-19 17:54 ` [PATCH v7 03/24] iommu/sva: Add PASID helpers Jean-Philippe Brucker
2020-05-20  2:41   ` Lu Baolu
2020-05-19 17:54 ` [PATCH v7 04/24] iommu: Add a page fault handler Jean-Philippe Brucker
2020-05-20  6:42   ` Lu Baolu
2020-11-11 13:57     ` Jean-Philippe Brucker [this message]
2020-11-11 23:11       ` Lu Baolu
2020-05-29  9:18   ` Xiang Zheng
2020-11-11 13:57     ` Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 05/24] arm64: mm: Add asid_gen_match() helper Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 06/24] arm64: mm: Pin down ASIDs for sharing mm with devices Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 07/24] iommu/io-pgtable-arm: Move some definitions to a header Jean-Philippe Brucker
2020-05-21 14:16   ` Will Deacon
2020-05-19 17:54 ` [PATCH v7 08/24] iommu/arm-smmu-v3: Manage ASIDs with xarray Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 09/24] arm64: cpufeature: Export symbol read_sanitised_ftr_reg() Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 10/24] iommu/arm-smmu-v3: Share process page tables Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 11/24] iommu/arm-smmu-v3: Seize private ASID Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 12/24] iommu/arm-smmu-v3: Add support for VHE Jean-Philippe Brucker
2020-05-21 14:16   ` Will Deacon
2020-05-19 17:54 ` [PATCH v7 13/24] iommu/arm-smmu-v3: Enable broadcast TLB maintenance Jean-Philippe Brucker
2020-05-21 14:17   ` Will Deacon
2020-05-21 14:38     ` Marc Zyngier
2020-05-22 10:17       ` Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 14/24] iommu/arm-smmu-v3: Add SVA feature checking Jean-Philippe Brucker
2020-05-21 14:17   ` Will Deacon
2020-05-19 17:54 ` [PATCH v7 15/24] iommu/arm-smmu-v3: Add SVA device feature Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 16/24] iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind() Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 17/24] iommu/arm-smmu-v3: Hook up ATC invalidation to mm ops Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 18/24] iommu/arm-smmu-v3: Add support for Hardware Translation Table Update Jean-Philippe Brucker
2020-05-21 11:12   ` Will Deacon
2020-05-27  3:00   ` Xiang Zheng
2020-05-27  8:41     ` Jean-Philippe Brucker
2020-08-28  9:28   ` Zenghui Yu
2020-09-16 14:11     ` Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 19/24] iommu/arm-smmu-v3: Maintain a SID->device structure Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 20/24] dt-bindings: document stall property for IOMMU masters Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 21/24] iommu/arm-smmu-v3: Add stall support for platform devices Jean-Philippe Brucker
2020-06-01 12:42   ` Shameerali Kolothum Thodi
2020-06-02  9:38     ` Jean-Philippe Brucker
2020-06-02 10:31       ` Shameerali Kolothum Thodi
2020-06-02 11:46         ` Jean-Philippe Brucker
2020-06-02 12:12           ` Shameerali Kolothum Thodi
2020-06-03  7:38             ` Jean-Philippe Brucker
2020-05-19 17:55 ` [PATCH v7 22/24] PCI/ATS: Add PRI stubs Jean-Philippe Brucker
2020-05-19 17:55 ` [PATCH v7 23/24] PCI/ATS: Export PRI functions Jean-Philippe Brucker
2020-05-19 17:55 ` [PATCH v7 24/24] iommu/arm-smmu-v3: Add support for PRI Jean-Philippe Brucker
2020-05-21 10:35 ` [PATCH v7 00/24] iommu: Shared Virtual Addressing for SMMUv3 Will Deacon
2020-05-21 14:17   ` Will Deacon

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