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Re: [PATCH V2 2/7] xen/grants: support allocating consecutive grants
- To: Oleksandr <olekstysh@xxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
- From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- Date: Wed, 11 May 2022 17:09:33 -0400
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, Juergen Gross <jgross@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, "Michael S. Tsirkin" <mst@xxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>
- Delivery-date: Wed, 11 May 2022 21:10:14 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 5/11/22 2:00 PM, Oleksandr wrote:
On 07.05.22 21:19, Oleksandr Tyshchenko wrote:
Hello Boris, Stefano
From: Juergen Gross <jgross@xxxxxxxx>
For support of virtio via grant mappings in rare cases larger mappings
using consecutive grants are needed. Support those by adding a bitmap
of free grants.
As consecutive grants will be needed only in very rare cases (e.g. when
configuring a virtio device with a multi-page ring), optimize for the
normal case of non-consecutive allocations.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
Changes RFC -> V1:
- no changes
Changes V1 -> V2:
- no changes
May I please ask for the review here?
I had a quick look but I am stuck on get_free_seq(), I need to stare at it some
more. Unless someone else reviews this, I will try to get to this in the next
couple of days.
One thing I did notice is
@@ -1452,6 +1624,13 @@ int gnttab_init(void)
}
}
+ i = gnttab_interface->grefs_per_grant_frame * max_nr_grant_frames;
+ gnttab_free_bitmap = bitmap_zalloc(i, GFP_KERNEL);
+ if (!gnttab_free_bitmap) {
+ ret = -ENOMEM;
+ goto ini_nomem;
+ }
This overwrites 'i' and will break error handling at ini_nomem.
-boris
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