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Re: [Xen-devel] [PATCH] xen/privcmd: Support correctly 64KB page granularity when mapping memory
Hi,
It has been reviewed-by Boris but I don't see the patch queued. Would it
be possible to queue it for 4.12?
Cheers,
On 01/06/17 21:41, Boris Ostrovsky wrote:
On 06/01/2017 11:38 AM, Julien Grall wrote:
Hi Boris,
On 01/06/17 16:16, Boris Ostrovsky wrote:
On 06/01/2017 10:01 AM, Julien Grall wrote:
Hi Boris,
On 01/06/17 14:33, Boris Ostrovsky wrote:
On 06/01/2017 08:50 AM, Julien Grall wrote:
Hi Boris,
On 31/05/17 14:54, Boris Ostrovsky wrote:
On 05/31/2017 09:03 AM, Julien Grall wrote:
Commit 5995a68 "xen/privcmd: Add support for Linux 64KB page
granularity" did
not go far enough to support 64KB in mmap_batch_fn.
The variable 'nr' is the number of 4KB chunk to map. However, when
Linux
is using 64KB page granularity the array of pages
(vma->vm_private_data)
contain one page per 64KB. Fix it by incrementing st->index
correctly.
Furthermore, st->va is not correctly incremented as PAGE_SIZE !=
XEN_PAGE_SIZE.
Fixes: 5995a68 ("xen/privcmd: Add support for Linux 64KB page
granularity")
CC: stable@xxxxxxxxxxxxxxx
Reported-by: Feng Kan <fkan@xxxxxxx>
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
drivers/xen/privcmd.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 7a92a5e1d40c..feca75b07fdd 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -362,8 +362,8 @@ static int mmap_batch_fn(void *data, int nr,
void *state)
st->global_error = 1;
}
}
- st->va += PAGE_SIZE * nr;
- st->index += nr;
+ st->va += XEN_PAGE_SIZE * nr;
+ st->index += nr / XEN_PFN_PER_PAGE;
return 0;
}
Are we still using PAGE_MASK for xen_remap_domain_gfn_array()?
Do you mean in the xen_xlate_remap_gfn_array implementation? If so
there are no use of PAGE_MASK as the code has been converted to
support 64K page granularity.
If you mean the x86 version of xen_remap_domain_gfn_array, then we
don't really care as x86 only use 4KB page granularity.
I meant right above the change that you made. Should it also be
replaced
with XEN_PAGE_MASK? (Sorry for being unclear.)
Oh. The code in xen_remap_domain_gfn_array is relying on st->va to be
page aligned. So I think we want to keep PAGE_MASK here.
Doe this imply then that 'nr' 4K pages is integral number of PAGE_SIZE
(i.e. (nr*XEN_PAGE_SIZE) % PAGE_SIZE == 0) and if yes --- do we test
this somewhere? I don't see it.
I now see that this should (obviously) stay as PAGE_MASK, so
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
but
nr might be smaller for the last batch. But all the intermediate batch
should have ((nr * XEN_PAGE_SIZE) % PAGE_SIZE == 0).
how can we have nr not covering full PAGE_SIZEs? If you are using 64K
pages, how can you map, say, only 4K (if nr==1)?
-boris
I think the BUILD_BUG_ON in privcmd_ioctl_mmap_batch ensure that all
the intermediate batch will always be an integral number of PAGE_SIZE.
Cheers,
--
Julien Grall
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