Hi Jiandi,
Please respect the netiquette and wrap line to 70-75 characters.
On 20/12/2016 06:02, Jiandi An wrote:
On 12/19/16 12:49, Stefano Stabellini wrote:
On Mon, 19 Dec 2016, Juergen Gross wrote:
On 19/12/16 03:56, Jiandi An wrote:
Thanks for you comments. xatp is passed to XEN via the hypervisor call in each
loop.
XEN touches xatp and returns it back. For example XEN returns error of
underlying mapping call in the err[] array in xatp. (The err[] is not checked
after the hypervisor call returns and it's a bug to be addressed in a separate
patch) XEN could theoretically corrupt xatp when it's returned. And the loop
would go on to the next iteration passing in whatever that's in xatp returned
by the previous hypervisor call. Harder to debug in my opinion if xatp get
corrupted by XEN somehow when a bug is introduced in XEN. At first I put the
memset of xatp at the beginning outside of the loop. But I thought it's better
to initialize xatp that's passed in each time a hypervisor call is made so we
know exactly we set going into the hypervisor call.
If you move struct xen_add_to_physmap_range in the loop, the compiler
will initialize and zeroed for you the structure at each loop. I.e
for (i = 0; i < count; i++) {
struct xen_add_to_physmap_range xapt = ....
}
Cheers,
--
Julien Grall
