IOMMU Archive on lore.kernel.org
 help / color / Atom feed
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: devicetree@vger.kernel.org, kevin.tian@intel.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-pci@vger.kernel.org, robin.murphy@arm.com,
	linux-mm@kvack.org, iommu@lists.linux-foundation.org,
	Dimitri Sivanich <sivanich@sgi.com>,
	catalin.marinas@arm.com, zhangfei.gao@linaro.org,
	will@kernel.org, christian.koenig@amd.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 01/25] mm/mmu_notifiers: pass private data down to alloc_notifier()
Date: Tue, 14 Apr 2020 15:09:12 -0300
Message-ID: <20200414180912.GH5100@ziepe.ca> (raw)
In-Reply-To: <20200414170252.714402-2-jean-philippe@linaro.org>

On Tue, Apr 14, 2020 at 07:02:29PM +0200, Jean-Philippe Brucker wrote:
> The new allocation scheme introduced by commit 2c7933f53f6b
> ("mm/mmu_notifiers: add a get/put scheme for the registration") provides
> a convenient way for users to attach notifier data to an mm. However, it
> would be even better to create this notifier data atomically.
> 
> Since the alloc_notifier() callback only takes an mm argument at the
> moment, some users have to perform the allocation in two times.
> alloc_notifier() initially creates an incomplete structure, which is
> then finalized using more context once mmu_notifier_get() returns. This
> second step requires extra care to order memory accesses against live
> invalidation.
> 
> The IOMMU SVA module, which attaches an mm to multiple devices,
> exemplifies this situation. In essence it does:
> 
> 	mmu_notifier_get()
> 	  alloc_notifier()
> 	     A = kzalloc()
> 	  /* MMU notifier is published */
> 	A->ctx = ctx;				// (1)
> 	device->A = A;
> 	list_add_rcu(device, A->devices);	// (2)
> 
> The invalidate notifier, which may start running before A is fully
> initialized, does the following:
> 
> 	io_mm_invalidate(A)
> 	  list_for_each_entry_rcu(device, A->devices)
> 	    device->invalidate(A->ctx)

This could probably also have been reliably fixed by not having A->ctx
be allocated memory, but inlined into the notifier struct

But I can't think of a down side to not add a params either.

Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

Regards,
Jason
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-14 17:02 [PATCH v5 00/25] iommu: Shared Virtual Addressing and SMMUv3 support Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 01/25] mm/mmu_notifiers: pass private data down to alloc_notifier() Jean-Philippe Brucker
2020-04-14 18:09   ` Jason Gunthorpe [this message]
2020-04-14 17:02 ` [PATCH v5 02/25] iommu/sva: Manage process address spaces Jean-Philippe Brucker
2020-04-16  7:28   ` Christoph Hellwig
2020-04-16  8:54     ` Jean-Philippe Brucker
2020-04-16 12:13       ` Christoph Hellwig
2020-04-20  7:42         ` Jean-Philippe Brucker
2020-04-20  8:10           ` Christoph Hellwig
2020-04-20 11:44             ` Christian König
2020-04-20 11:55               ` Christoph Hellwig
2020-04-20 12:40                 ` Christian König
2020-04-20 15:00                   ` Felix Kuehling
2020-04-20 17:44                     ` Jacob Pan
2020-04-20 17:52                       ` Felix Kuehling
2020-04-20 13:57           ` Jason Gunthorpe
2020-04-20 17:48             ` Jacob Pan
2020-04-20 18:14               ` Fenghua Yu
2020-04-21  8:55                 ` Christoph Hellwig
2020-04-14 17:02 ` [PATCH v5 03/25] iommu: Add a page fault handler Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 04/25] iommu/sva: Search mm by PASID Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 05/25] iommu/iopf: Handle mm faults Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 06/25] iommu/sva: Register page fault handler Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 07/25] arm64: mm: Add asid_gen_match() helper Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 08/25] arm64: mm: Pin down ASIDs for sharing mm with devices Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 09/25] iommu/io-pgtable-arm: Move some definitions to a header Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 10/25] iommu/arm-smmu-v3: Manage ASIDs with xarray Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 11/25] arm64: cpufeature: Export symbol read_sanitised_ftr_reg() Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 12/25] iommu/arm-smmu-v3: Share process page tables Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 13/25] iommu/arm-smmu-v3: Seize private ASID Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 14/25] iommu/arm-smmu-v3: Add support for VHE Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 15/25] iommu/arm-smmu-v3: Enable broadcast TLB maintenance Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 16/25] iommu/arm-smmu-v3: Add SVA feature checking Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 17/25] iommu/arm-smmu-v3: Implement mm operations Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 18/25] iommu/arm-smmu-v3: Hook up ATC invalidation to mm ops Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 19/25] iommu/arm-smmu-v3: Add support for Hardware Translation Table Update Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 20/25] iommu/arm-smmu-v3: Maintain a SID->device structure Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 21/25] dt-bindings: document stall property for IOMMU masters Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 22/25] iommu/arm-smmu-v3: Add stall support for platform devices Jean-Philippe Brucker
2020-04-14 17:02 ` [PATCH v5 23/25] PCI/ATS: Add PRI stubs Jean-Philippe Brucker
2020-04-14 18:03   ` Kuppuswamy, Sathyanarayanan
2020-04-14 17:02 ` [PATCH v5 24/25] PCI/ATS: Export PRI functions Jean-Philippe Brucker
2020-04-14 18:03   ` Kuppuswamy, Sathyanarayanan
2020-04-14 17:02 ` [PATCH v5 25/25] iommu/arm-smmu-v3: Add support for PRI Jean-Philippe Brucker

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200414180912.GH5100@ziepe.ca \
    --to=jgg@ziepe.ca \
    --cc=akpm@linux-foundation.org \
    --cc=arnd@arndb.de \
    --cc=catalin.marinas@arm.com \
    --cc=christian.koenig@amd.com \
    --cc=devicetree@vger.kernel.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jean-philippe@linaro.org \
    --cc=kevin.tian@intel.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=sivanich@sgi.com \
    --cc=will@kernel.org \
    --cc=zhangfei.gao@linaro.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

IOMMU Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-iommu/0 linux-iommu/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-iommu linux-iommu/ https://lore.kernel.org/linux-iommu \
		iommu@lists.linux-foundation.org
	public-inbox-index linux-iommu

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.linux-foundation.lists.iommu


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git