On Tue, Apr 30, 2024 at 06:58:43PM +0200, Roger Pau Monne wrote:
> Hello,
>
> The following series attempts to solve a shortcoming of HVM/PVH guests
> with the lack of support for foreign mappings. Such lack of support
> prevents using PVH based guests as stubdomains for example.
>
> Add support in a way similar to how it was done on Arm, by iterating
> over the p2m based on the maximum gfn.
>
> Mostly untested, sending early in case it could be considered for 4.19.
I've now tested this using the following dummy XTF test:
void test_main(void)
{
unsigned long idxs = 0;
xen_pfn_t gpfns = 0;
int errs = 0, error;
struct xen_add_to_physmap_batch add = {
.domid = DOMID_SELF,
.space = XENMAPSPACE_gmfn_foreign,
.u.foreign_domid = 0,
.size = 1,
.idxs.p = &idxs,
.gpfns.p = &gpfns,
.errs.p = &errs,
};
error = hypercall_memory_op(XENMEM_add_to_physmap_batch, &add);
if ( error || errs )
xtf_error("add_to_physmap_batch failed: %d (errs: %d)\n", error, errs);
while ( 1 );
xtf_success(NULL);
}
And avoiding some of the permissions checks in Xen so that an
arbitrary domU could map dom0 gfn 0. I see count_info increasing by 1
until the XTF guest is killed, at which point the count_info goes back
to the value previous to the map.
Regards, Roger.
