Re: [PATCH] xen/privcmd: Support correctly 64KB page granularity when mapping memory

From: Julien Grall
Date: Thu Jun 01 2017 - 08:51:02 EST


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.

Cheers,

--
Julien Grall