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Re: [Xen-devel] Question on xc_gnttab_map_grant_ref()
- To: "King, Steven R" <steven.r.king@xxxxxxxxx>
- From: Christopher Clark <christopher.clark@xxxxxxxxxxxx>
- Date: Thu, 3 Nov 2005 22:59:43 +0000
- Cc: NAHieu <nahieu@xxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
- Delivery-date: Thu, 03 Nov 2005 22:59:58 +0000
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The implementation is indeed incomplete and I agree that grant
references are not the correct interface for the kernel to expose to
user space. MarkW's mmap work-in-progress ought be far more suitable.
The main use of xc_gnttab stuff has been for debugging new clients
using the grant tables -- it's been handy to modify and read them from
userspace to figure out what's going on, but clearly this isn't
something you'd want in a production kernel, which is why it's disabled.
Christopher
On 11/3/05, King, Steven R <steven.r.king@xxxxxxxxx> wrote:
I've been looking at xc_gnttab stuff lately too and the current
implementation is incomplete. For example, I don't see a way to acquire
a grant reference from user space, so the xc_gnttab functions taking a
reference are unusable.
IMO, grant references are kernel level implementation details that
should not be exposed to user-mode anyway. Instead, user-mode needs
IOCTLs to share pages with a remote domain and to map those shared pages
within the remote end. If the kernel implements this functionality with
grant tables, then great; in the future it may do something else. I
hope to have a patch to offer for this eventually.
-steve
-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
] On Behalf Of NAHieu
Sent: Thursday, November 03, 2005 4:53 AM
To: xen-devel
Subject: [Xen-devel] Question on xc_gnttab_map_grant_ref()
Hi,
I am writing a kermel module in DomU, and this module grants a page of
memory to Dom0. Then in Dom0 I try to grant_map it with
xc_gnttab_map_grant_ref()
But this function requires a flag, and I don't know which option to give
it. I tried with either GNTMAP_application_map or
GTF_reading|GTF_writing, but I always got this error:
ERROR: do_gnttab_op: HYPERVISOR_grant_table_op failed: -1
Anybody please tell me how to use xc_gnttab_map_grant_ref() properly in
Dom0's userspace?
Many thanks.
Hieu
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