/* Atomically look up a GFN and take a reference count on the backing page. */
struct page_info *get_page_from_gfn_p2m(
struct domain *d, struct p2m_domain *p2m, unsigned long gfn,
p2m_type_t *t, p2m_access_t *a, p2m_query_t q)
{
struct page_info *page = NULL;
p2m_access_t _a;
p2m_type_t _t;
mfn_t mfn;
/* Allow t or a to be NULL */
t = t ?: &_t;
a = a ?: &_a;
if ( likely(!p2m_locked_by_me(p2m)) )
{
/* Fast path: look up and get out */
p2m_read_lock(p2m);
mfn = __get_gfn_type_access(p2m, gfn, t, a, 0, NULL, 0);
if ( (p2m_is_ram(*t) || p2m_is_grant(*t))
&& mfn_valid(mfn)
&& !((q & P2M_UNSHARE) && p2m_is_shared(*t)) )
{
page = mfn_to_page(mfn);
if ( !get_page(page, d)
/* Page could be shared */
&& !get_page(page, dom_cow) )
page = NULL;
}
p2m_read_unlock(p2m);
if ( page )
return page;
/* Error path: not a suitable GFN at all */
if ( !p2m_is_ram(*t) && !p2m_is_paging(*t) && !p2m_is_pod(*t) )
return NULL;
}
/* Slow path: take the write lock and do fixups */
mfn = get_gfn_type_access(p2m, gfn, t, a, q, NULL);
if ( p2m_is_ram(*t) && mfn_valid(mfn) )
{
page = mfn_to_page(mfn);
if ( !get_page(page, d) )
page = NULL;
}
put_gfn(d, gfn);
return page;
}
int p2m_set_altp2m_mem_access(struct domain *d, struct p2m_domain *hp2m,
struct p2m_domain *ap2m, p2m_access_t a,
gfn_t gfn)
{
mfn_t mfn;
p2m_type_t t;
p2m_access_t old_a;
unsigned int page_order;
unsigned long gfn_l = gfn_x(gfn);
int rc;
mfn = ap2m->get_entry(ap2m, gfn_l, &t, &old_a, 0, NULL, NULL);
/* Check host p2m if no valid entry in alternate */
if ( !mfn_valid(mfn) )
{
mfn = __get_gfn_type_access(hp2m, gfn_l, &t, &old_a,
P2M_ALLOC | P2M_UNSHARE, &page_order, 0);
rc = -ESRCH;
if ( !mfn_valid(mfn) || t != p2m_ram_rw )
return rc;
/* If this is a superpage, copy that first */
if ( page_order != PAGE_ORDER_4K )
{
unsigned long mask = ~((1UL << page_order) - 1);
unsigned long gfn2_l = gfn_l & mask;
mfn_t mfn2 = _mfn(mfn_x(mfn) & mask);
rc = ap2m->set_entry(ap2m, gfn2_l, mfn2, page_order, t, old_a, 1);
if ( rc )
return rc;
}
}
return ap2m->set_entry(ap2m, gfn_l, mfn, PAGE_ORDER_4K, t, a,
(current->domain != d));
}
