All of lore.kernel.org
 help / color / mirror / Atom feed
From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: michael.jamet@intel.com, linux-usb@vger.kernel.org,
	linux-kernel@vger.kernel.org, YehezkelShB@gmail.com,
	iommu@lists.linux-foundation.org, mario.limonciello@amd.com,
	andreas.noever@gmail.com, hch@lst.de
Subject: Re: [PATCH v3 3/4] thunderbolt: Make iommu_dma_protection more accurate
Date: Tue, 5 Apr 2022 15:09:07 +0300	[thread overview]
Message-ID: <YkwxY59ACqFF9jer@lahna> (raw)
In-Reply-To: <b1f89ea2ad38221e0b75783357b9afb53087061d.1649089693.git.robin.murphy@arm.com>

On Tue, Apr 05, 2022 at 11:41:03AM +0100, Robin Murphy wrote:
> Between me trying to get rid of iommu_present() and Mario wanting to
> support the AMD equivalent of DMAR_PLATFORM_OPT_IN, scrutiny has shown
> that the iommu_dma_protection attribute is being far too optimistic.
> Even if an IOMMU might be present for some PCI segment in the system,
> that doesn't necessarily mean it provides translation for the device(s)
> we care about. Furthermore, all that DMAR_PLATFORM_OPT_IN really does
> is tell us that memory was protected before the kernel was loaded, and
> prevent the user from disabling the intel-iommu driver entirely. While
> that lets us assume kernel integrity, what matters for actual runtime
> DMA protection is whether we trust individual devices, based on the
> "external facing" property that we expect firmware to describe for
> Thunderbolt ports.
> 
> It's proven challenging to determine the appropriate ports accurately
> given the variety of possible topologies, so while still not getting a
> perfect answer, by putting enough faith in firmware we can at least get
> a good bit closer. If we can see that any device near a Thunderbolt NHI
> has all the requisites for Kernel DMA Protection, chances are that it
> *is* a relevant port, but moreover that implies that firmware is playing
> the game overall, so we'll use that to assume that all Thunderbolt ports
> should be correctly marked and thus will end up fully protected.
> 
> CC: Mario Limonciello <mario.limonciello@amd.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

WARNING: multiple messages have this Message-ID (diff)
From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: joro@8bytes.org, baolu.lu@linux.intel.com,
	andreas.noever@gmail.com, michael.jamet@intel.com,
	YehezkelShB@gmail.com, iommu@lists.linux-foundation.org,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	mario.limonciello@amd.com, hch@lst.de
Subject: Re: [PATCH v3 3/4] thunderbolt: Make iommu_dma_protection more accurate
Date: Tue, 5 Apr 2022 15:09:07 +0300	[thread overview]
Message-ID: <YkwxY59ACqFF9jer@lahna> (raw)
In-Reply-To: <b1f89ea2ad38221e0b75783357b9afb53087061d.1649089693.git.robin.murphy@arm.com>

On Tue, Apr 05, 2022 at 11:41:03AM +0100, Robin Murphy wrote:
> Between me trying to get rid of iommu_present() and Mario wanting to
> support the AMD equivalent of DMAR_PLATFORM_OPT_IN, scrutiny has shown
> that the iommu_dma_protection attribute is being far too optimistic.
> Even if an IOMMU might be present for some PCI segment in the system,
> that doesn't necessarily mean it provides translation for the device(s)
> we care about. Furthermore, all that DMAR_PLATFORM_OPT_IN really does
> is tell us that memory was protected before the kernel was loaded, and
> prevent the user from disabling the intel-iommu driver entirely. While
> that lets us assume kernel integrity, what matters for actual runtime
> DMA protection is whether we trust individual devices, based on the
> "external facing" property that we expect firmware to describe for
> Thunderbolt ports.
> 
> It's proven challenging to determine the appropriate ports accurately
> given the variety of possible topologies, so while still not getting a
> perfect answer, by putting enough faith in firmware we can at least get
> a good bit closer. If we can see that any device near a Thunderbolt NHI
> has all the requisites for Kernel DMA Protection, chances are that it
> *is* a relevant port, but moreover that implies that firmware is playing
> the game overall, so we'll use that to assume that all Thunderbolt ports
> should be correctly marked and thus will end up fully protected.
> 
> CC: Mario Limonciello <mario.limonciello@amd.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>

  reply	other threads:[~2022-04-05 12:16 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-05 10:41 [PATCH v3 0/4] thunderbolt: Make iommu_dma_protection more accurate Robin Murphy
2022-04-05 10:41 ` Robin Murphy
2022-04-05 10:41 ` [PATCH v3 1/4] iommu: Introduce device_iommu_capable() Robin Murphy
2022-04-05 10:41   ` Robin Murphy
2022-04-06  5:28   ` Christoph Hellwig
2022-04-06  5:28     ` Christoph Hellwig
2022-04-06 10:32     ` Robin Murphy
2022-04-06 10:32       ` Robin Murphy
2022-04-05 10:41 ` [PATCH v3 2/4] iommu: Add capability for pre-boot DMA protection Robin Murphy
2022-04-05 10:41   ` Robin Murphy
2022-04-06 10:28   ` Lu Baolu
2022-04-06 10:28     ` Lu Baolu
2022-04-05 10:41 ` [PATCH v3 3/4] thunderbolt: Make iommu_dma_protection more accurate Robin Murphy
2022-04-05 10:41   ` Robin Murphy
2022-04-05 12:09   ` Mika Westerberg [this message]
2022-04-05 12:09     ` Mika Westerberg
2022-04-05 10:41 ` [PATCH v3 4/4] iommu/amd: Indicate whether DMA remap support is enabled Robin Murphy
2022-04-05 10:41   ` Robin Murphy
2022-04-06  5:28   ` Christoph Hellwig
2022-04-06  5:28     ` Christoph Hellwig

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=YkwxY59ACqFF9jer@lahna \
    --to=mika.westerberg@linux.intel.com \
    --cc=YehezkelShB@gmail.com \
    --cc=andreas.noever@gmail.com \
    --cc=hch@lst.de \
    --cc=iommu@lists.linux-foundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-usb@vger.kernel.org \
    --cc=mario.limonciello@amd.com \
    --cc=michael.jamet@intel.com \
    --cc=robin.murphy@arm.com \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.