On 25/03/2020 16:47, Tamas K Lengyel wrote:
On Wed, Mar 25, 2020 at 10:42 AM Julien Grall <jul...@xen.org> wrote:
Hi,
On 25/03/2020 16:34, Tamas K Lengyel wrote:
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 9f51370327..1ed7d13084 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -509,6 +509,12 @@ mfn_t __get_gfn_type_access(struct p2m_domain *p2m,
unsigned long gfn_l,
mfn = p2m->get_entry(p2m, gfn, t, a, q, page_order, NULL);
+ /* Check if we need to fork the page */
+ if ( (q & P2M_ALLOC) && p2m_is_hole(*t) &&
+ !mem_sharing_fork_page(p2m->domain, gfn, q & P2M_UNSHARE) )
+ mfn = p2m->get_entry(p2m, gfn, t, a, q, page_order, NULL);
+
+ /* Check if we need to unshare the page */
if ( (q & P2M_UNSHARE) && p2m_is_shared(*t) )
{
ASSERT(p2m_is_hostp2m(p2m));
@@ -588,7 +594,8 @@ struct page_info *p2m_get_page_from_gfn(
return page;
/* Error path: not a suitable GFN at all */
- if ( !p2m_is_ram(*t) && !p2m_is_paging(*t) && !p2m_is_pod(*t) )
+ if ( !p2m_is_ram(*t) && !p2m_is_paging(*t) && !p2m_is_pod(*t) &&
+ !mem_sharing_is_fork(p2m->domain) )
return NULL;
}
diff --git a/xen/common/domain.c b/xen/common/domain.c
index b4eb476a9c..62aed53a16 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1270,6 +1270,9 @@ int map_vcpu_info(struct vcpu *v, unsigned long gfn,
unsigned offset)
v->vcpu_info = new_info;
v->vcpu_info_mfn = page_to_mfn(page);
+#ifdef CONFIG_MEM_SHARING
+ v->vcpu_info_offset = offset;
There's no need to introduce this field, you can just use v->vcpu_info
& ~PAGE_MASK AFAICT.
Just doing what you suggest above results in:
mem_sharing.c:1603:55: error: invalid operands to binary & (have
‘vcpu_info_t * const’ {aka ‘union <anonymous> * const’} and ‘long
int’)
d_vcpu->vcpu_info & ~PAGE_MASK);
I can of course cast the vcpu_info pointer to (long int), it's just a
bit ugly. Thoughts?
FWIW, I will also need the offset for liveupdate. I have used (unsigned
long)v->vcpu_info & ~PAGE_MASK so far but this is not really pretty.
So I am all for either a new field or a macro hiding this uglyness.
A macro sounds like a good way to go, no need for an extra field if we
can calculate it based on the currently existing one. How about
#define VCPU_INFO_OFFSET(v) (((unsigned long)v->vcpu_info) & ~PAGE_MASK)
I was more thinking a generic macro to find the offset in a page.
PAGE_OFFSET(ptr) ((unsigned long)(ptr) & ~PAGE_MASK)
Anyway, I am happy either way.
Cheers,
--
Julien Grall
