From: Oleksandr <olekstysh@gmail.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>, Julien Grall <julien@xen.org>,
"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [RFC PATCH 6/6] arm/xen: Assign xen-virtio DMA ops for virtio devices in Xen guests
Date: Mon, 18 Apr 2022 00:05:08 +0300 [thread overview]
Message-ID: <f879622e-5656-deb1-1930-f0cd180a4ab1@gmail.com> (raw)
In-Reply-To: <YlpdBHKT1bYzZe2e@infradead.org>
On 16.04.22 09:07, Christoph Hellwig wrote:
Hello Christoph
> On Fri, Apr 15, 2022 at 03:02:45PM -0700, Stefano Stabellini wrote:
>> This makes sense overall. Considering that the swiotlb-xen case and the
>> virtio case are mutually exclusive, I would write it like this:
> Curious question: Why can't the same grant scheme also be used for
> non-virtio devices? I really hate having virtio hooks in the arch
> dma code. Why can't Xen just say in DT/ACPI that grants can be used
> for a given device?
In Xen system:
- the grants are not used for "non-virtualized" devices at all (platform
devices for the passthrough).
- the grants are widely used for "virtualized, but non-virtio" devices
(traditional Xen PV devices), but grants for these Xen PV devices
are used in a different way and *not* at the DMA ops level like in
current approach
Or I misunderstood your question?
This patch series tries to make things work with "virtio" devices in Xen
system without introducing any modifications to code under drivers/virtio.
We could avoid having virtio hooks in the arch DMA code, but we need to
trigger setting xen-virtio DMA ops for the virtio device from some other
place.
For example, the following code would also work, but requires altering
virtio_mmio_probe():
diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 56128b9..8f48491 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -615,6 +615,9 @@ static int virtio_mmio_probe(struct platform_device
*pdev)
DMA_BIT_MASK(32 +
PAGE_SHIFT));
} else {
rc = dma_set_mask_and_coherent(&pdev->dev,
DMA_BIT_MASK(64));
+
+ if (arch_has_restricted_virtio_memory_access())
+ xen_virtio_setup_dma_ops(&pdev->dev);
}
if (rc)
rc = dma_set_mask_and_coherent(&pdev->dev,
DMA_BIT_MASK(32));
Another possible option could be to introduce local init function in
drivers/xen/xen-virtio.c to scan the device tree and set xen-virtio DMA
ops for all devices with the
"xen,dev-domid" property.
What do you think?
--
Regards,
Oleksandr Tyshchenko
next prev parent reply other threads:[~2022-04-17 21:05 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-14 19:19 [RFC PATCH 0/6] virtio: Solution to restrict memory access under Xen using xen-virtio DMA ops layer Oleksandr Tyshchenko
2022-04-14 19:19 ` [RFC PATCH 1/6] xen/grants: support allocating consecutive grants Oleksandr Tyshchenko
2022-04-14 19:19 ` [RFC PATCH 2/6] virtio: add option to restrict memory access under Xen Oleksandr Tyshchenko
2022-04-14 19:43 ` H. Peter Anvin
2022-04-15 15:20 ` Oleksandr
2022-04-15 22:01 ` Stefano Stabellini
2022-04-17 17:02 ` Oleksandr
2022-04-18 19:11 ` Stefano Stabellini
2022-04-19 6:21 ` Juergen Gross
2022-04-19 6:37 ` Oleksandr
2022-04-14 19:19 ` [RFC PATCH 3/6] dt-bindings: xen: Add xen,dev-domid property description for xen-virtio layer Oleksandr Tyshchenko
2022-04-15 22:01 ` Stefano Stabellini
2022-04-17 17:24 ` Oleksandr
2022-04-14 19:19 ` [RFC PATCH 4/6] virtio: Various updates to xen-virtio DMA ops layer Oleksandr Tyshchenko
2022-04-15 22:02 ` Stefano Stabellini
2022-04-17 18:21 ` Oleksandr
2022-04-18 19:11 ` Stefano Stabellini
2022-04-19 6:58 ` Juergen Gross
2022-04-19 7:07 ` Oleksandr
2022-04-16 6:05 ` Christoph Hellwig
2022-04-17 18:39 ` Oleksandr
2022-04-14 19:19 ` [RFC PATCH 5/6] arm/xen: Introduce xen_setup_dma_ops() Oleksandr Tyshchenko
2022-04-15 22:02 ` Stefano Stabellini
2022-04-17 18:43 ` Oleksandr
2022-04-14 19:19 ` [RFC PATCH 6/6] arm/xen: Assign xen-virtio DMA ops for virtio devices in Xen guests Oleksandr Tyshchenko
2022-04-15 22:02 ` Stefano Stabellini
2022-04-16 6:07 ` Christoph Hellwig
2022-04-17 21:05 ` Oleksandr [this message]
2022-04-18 19:11 ` Stefano Stabellini
2022-04-19 12:17 ` Oleksandr
2022-04-19 14:48 ` Juergen Gross
2022-04-19 17:11 ` Oleksandr
2022-04-20 0:23 ` Stefano Stabellini
2022-04-20 9:00 ` Oleksandr
2022-04-20 22:49 ` Stefano Stabellini
2022-04-17 19:20 ` Oleksandr
2022-04-15 7:41 ` [RFC PATCH 0/6] virtio: Solution to restrict memory access under Xen using xen-virtio DMA ops layer Christoph Hellwig
2022-04-15 10:04 ` Oleksandr
2022-04-15 8:44 ` Michael S. Tsirkin
2022-04-15 15:29 ` Oleksandr
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