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From: Srivatsa Vaddagiri <vatsa@codeaurora.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: tsoni@codeaurora.org, virtio-dev@lists.oasis-open.org,
	will@kernel.org, konrad.wilk@oracle.com, jan.kiszka@siemens.com,
	jasowang@redhat.com, christoffer.dall@arm.com,
	pratikp@codeaurora.org,
	virtualization@lists.linux-foundation.org,
	iommu@lists.linux-foundation.org, stefano.stabellini@xilinx.com,
	alex.bennee@linaro.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/5] virtio: Add bounce DMA ops
Date: Wed, 29 Apr 2020 15:39:53 +0530	[thread overview]
Message-ID: <20200429100953.GE5097@quicinc.com> (raw)
In-Reply-To: <20200429055125-mutt-send-email-mst@kernel.org>

* Michael S. Tsirkin <mst@redhat.com> [2020-04-29 05:52:05]:

> > > So it seems that with modern Linux, all one needs
> > > to do on x86 is mark the device as untrusted.
> > > It's already possible to do this with ACPI and with OF - would that be
> > > sufficient for achieving what this patchset is trying to do?
> > 
> > In my case, its not sufficient to just mark virtio device untrusted and thus
> > activate the use of swiotlb. All of the secondary VM memory, including those
> > allocate by swiotlb driver, is private to it.
> 
> So why not make the bounce buffer memory shared then?

Its a limitation by our hypervisor. When a secondary VM is created, two
memory segments are allocated - one private and other shared. There is no
provision for the secondary VM to make part of its private memory shared after
it boots. I can perhaps consider a change in swiotlb driver to accept the second
shared memory segment as its main working area (rather than allocate its own).

That would still not work I think where swiotlb is used for pass-thr devices
(when private memory is fine) as well as virtio devices (when shared memory is
required).

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

WARNING: multiple messages have this Message-ID (diff)
From: Srivatsa Vaddagiri <vatsa@codeaurora.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>,
	tsoni@codeaurora.org, virtio-dev@lists.oasis-open.org,
	konrad.wilk@oracle.com, jan.kiszka@siemens.com,
	jasowang@redhat.com, christoffer.dall@arm.com,
	virtualization@lists.linux-foundation.org,
	alex.bennee@linaro.org, iommu@lists.linux-foundation.org,
	stefano.stabellini@xilinx.com, will@kernel.org,
	linux-kernel@vger.kernel.org, pratikp@codeaurora.org
Subject: Re: [PATCH 5/5] virtio: Add bounce DMA ops
Date: Wed, 29 Apr 2020 15:39:53 +0530	[thread overview]
Message-ID: <20200429100953.GE5097@quicinc.com> (raw)
In-Reply-To: <20200429055125-mutt-send-email-mst@kernel.org>

* Michael S. Tsirkin <mst@redhat.com> [2020-04-29 05:52:05]:

> > > So it seems that with modern Linux, all one needs
> > > to do on x86 is mark the device as untrusted.
> > > It's already possible to do this with ACPI and with OF - would that be
> > > sufficient for achieving what this patchset is trying to do?
> > 
> > In my case, its not sufficient to just mark virtio device untrusted and thus
> > activate the use of swiotlb. All of the secondary VM memory, including those
> > allocate by swiotlb driver, is private to it.
> 
> So why not make the bounce buffer memory shared then?

Its a limitation by our hypervisor. When a secondary VM is created, two
memory segments are allocated - one private and other shared. There is no
provision for the secondary VM to make part of its private memory shared after
it boots. I can perhaps consider a change in swiotlb driver to accept the second
shared memory segment as its main working area (rather than allocate its own).

That would still not work I think where swiotlb is used for pass-thr devices
(when private memory is fine) as well as virtio devices (when shared memory is
required).

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation

  reply	other threads:[~2020-04-29 10:10 UTC|newest]

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-28 11:39 [PATCH 0/5] virtio on Type-1 hypervisor Srivatsa Vaddagiri
2020-04-28 11:39 ` Srivatsa Vaddagiri
2020-04-28 11:39 ` [PATCH 1/5] swiotlb: Introduce concept of swiotlb_pool Srivatsa Vaddagiri
2020-04-28 11:39   ` Srivatsa Vaddagiri
2020-04-29  0:31   ` kbuild test robot
2020-04-29  0:31     ` kbuild test robot
2020-04-29  0:31     ` kbuild test robot
2020-04-29  0:31     ` kbuild test robot
2020-04-28 11:39 ` [PATCH 2/5] swiotlb: Allow for non-linear mapping between paddr and vaddr Srivatsa Vaddagiri
2020-04-28 11:39   ` Srivatsa Vaddagiri
2020-04-28 11:39 ` [PATCH 3/5] swiotlb: Add alloc and free APIs Srivatsa Vaddagiri
2020-04-28 11:39   ` Srivatsa Vaddagiri
2020-04-30  4:18   ` kbuild test robot
2020-04-30  4:18     ` kbuild test robot
2020-04-30  4:18     ` kbuild test robot
2020-04-30  4:18     ` kbuild test robot
2020-04-28 11:39 ` [PATCH 4/5] swiotlb: Add API to register new pool Srivatsa Vaddagiri
2020-04-28 11:39   ` Srivatsa Vaddagiri
2020-04-28 11:39 ` [PATCH 5/5] virtio: Add bounce DMA ops Srivatsa Vaddagiri
2020-04-28 11:39   ` Srivatsa Vaddagiri
2020-04-28 16:17   ` Michael S. Tsirkin
2020-04-28 16:17     ` Michael S. Tsirkin
2020-04-28 16:17     ` [virtio-dev] " Michael S. Tsirkin
2020-04-28 17:49     ` Srivatsa Vaddagiri
2020-04-28 17:49       ` Srivatsa Vaddagiri
2020-04-28 17:49       ` Srivatsa Vaddagiri
2020-04-28 20:41       ` Michael S. Tsirkin
2020-04-28 20:41         ` Michael S. Tsirkin
2020-04-28 20:41         ` [virtio-dev] " Michael S. Tsirkin
2020-04-28 23:04         ` Stefano Stabellini
2020-04-28 23:04           ` Stefano Stabellini
2020-04-29  4:09           ` Srivatsa Vaddagiri
2020-04-29  4:09             ` Srivatsa Vaddagiri
2020-04-29  2:22         ` Lu Baolu
2020-04-29  2:22           ` Lu Baolu
2020-04-29  4:57           ` Michael S. Tsirkin
2020-04-29  4:57             ` Michael S. Tsirkin
2020-04-29  4:57             ` [virtio-dev] " Michael S. Tsirkin
2020-04-29  5:42             ` Lu Baolu
2020-04-29  5:42               ` Lu Baolu
2020-04-29  6:50               ` Michael S. Tsirkin
2020-04-29  6:50                 ` Michael S. Tsirkin
2020-04-29  6:50                 ` [virtio-dev] " Michael S. Tsirkin
2020-04-29  7:01                 ` Lu Baolu
2020-04-29  7:01                   ` Lu Baolu
2020-04-29  9:44                 ` Srivatsa Vaddagiri
2020-04-29  9:44                   ` Srivatsa Vaddagiri
2020-04-29  9:52                   ` Michael S. Tsirkin
2020-04-29  9:52                     ` Michael S. Tsirkin
2020-04-29  9:52                     ` [virtio-dev] " Michael S. Tsirkin
2020-04-29 10:09                     ` Srivatsa Vaddagiri [this message]
2020-04-29 10:09                       ` Srivatsa Vaddagiri
2020-04-29 10:20                       ` Michael S. Tsirkin
2020-04-29 10:20                         ` Michael S. Tsirkin
2020-04-29 10:20                         ` [virtio-dev] " Michael S. Tsirkin
2020-04-29 10:26                         ` Jan Kiszka
2020-04-29 10:26                           ` Jan Kiszka
2020-04-29 10:26                           ` [virtio-dev] " Jan Kiszka
2020-04-29 10:45                           ` Michael S. Tsirkin
2020-04-29 10:45                             ` Michael S. Tsirkin
2020-04-29 10:45                             ` [virtio-dev] " Michael S. Tsirkin
2020-04-29 10:55                             ` Jan Kiszka
2020-04-29 10:55                               ` Jan Kiszka
2020-04-29 10:55                               ` Jan Kiszka
2020-04-29 10:55                               ` [virtio-dev] " Jan Kiszka
2020-04-29 10:34                         ` Srivatsa Vaddagiri
2020-04-29 10:34                           ` Srivatsa Vaddagiri
2020-04-30 15:20                         ` Konrad Rzeszutek Wilk
2020-04-30 15:20                           ` Konrad Rzeszutek Wilk
2020-04-30 15:20                           ` Konrad Rzeszutek Wilk
2020-04-29  3:35         ` Srivatsa Vaddagiri
2020-04-29  3:35           ` Srivatsa Vaddagiri
2020-04-28 21:35   ` kbuild test robot
2020-04-28 21:35     ` kbuild test robot
2020-04-28 21:35     ` kbuild test robot
2020-04-28 21:35     ` kbuild test robot
2020-04-28 22:18   ` kbuild test robot
2020-04-28 22:18     ` kbuild test robot
2020-04-28 22:18     ` kbuild test robot
2020-04-28 22:18     ` kbuild test robot
2020-04-28 22:53   ` Stefano Stabellini
2020-04-28 22:53     ` Stefano Stabellini
2020-04-29 21:06   ` kbuild test robot
2020-04-29 21:06     ` kbuild test robot
2020-04-29 21:06     ` kbuild test robot
2020-04-29 21:06     ` kbuild test robot
2020-04-29 21:06   ` [RFC PATCH] virtio: virtio_pool can be static kbuild test robot
2020-04-29 21:06     ` kbuild test robot
2020-04-29 21:06     ` kbuild test robot
2020-04-29 21:06     ` kbuild test robot

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