On 05/12/2015 05:43 PM, Ian Campbell wrote:
On Tue, 2015-05-12 at 17:24 +0800, Yang Hongyang wrote:
On 05/12/2015 04:19 PM, Ian Campbell wrote:
On Tue, 2015-05-12 at 15:18 +0800, Yang Hongyang wrote:
On 05/11/2015 07:53 PM, Ian Campbell wrote:
On Fri, 2015-05-08 at 17:33 +0800, Yang Hongyang wrote:
Define a user pointer that can access the hypercall buffer data
Useful when you only need to access the hypercall buffer data
Can you expand on this please, I think the context is a hypercall buffer
passed as an argument or as a member of a struct. Please describe why
DECLARE_HYPERCALL_BUFFER_ARGUMENT and/or DECLARE_HYPERCALL_BUFFER_SHADOW
are not usable here.
There are cases that we only need to use the hypercall buffer data, and do
not use the xc_hypercall_buffer_t struct.
DECLARE_HYPERCALL_BUFFER_ARGUMENT will only define a xc_hypercall_buffer_t,
while DECLARE_HYPERCALL_BUFFER_SHADOW do define a user pointer that can allow
us to access the hypercall buffer data but it also define a
xc_hypercall_buffer_t that we don't use, the compiler will report arg unused
error.
The cases for example:
In send_all_pages(), we only need to use the haypercall buffer data which is a
dirty bitmap, we set the dirty bitmap to all dirty and call send_dirty_pages,
we will not use the xc_hypercall_buffer_t and hypercall to retrive the dirty
bitmap.
In send_some_pages(), we will also only need to use the dirty_bitmap. the
retrive dirty bitmap hypercall are done by the caller.
Thanks. Please include the bulk of this description in the commit
message.
However, perhaps we should just mark the xc_hypercall_buffer_t as
potentially unused, by tagging it with __attribute__((unused)), in some
or all of the DECLARE_HYPERCALL_* variants. Then I think you could use
DECLARE_HYPERCALL_BUFFER_SHADOW as is?
If __attribute__((unused)) won't cause other problems here, I also prefer
to add this to DECLARE_HYPERCALL_BUFFER_SHADOW instead of create another
macro, I think only DECLARE_HYPERCALL_BUFFER_SHADOW may need to set this
attribute because this is a shadow, we might not use the xc_hypercall_buffer_t
which already allocated.
We can certainly start from there and consider other such additions as
the need arises.
OK, thanks, will do in the next version.
Ian.
.
--
Thanks,
Yang.
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
