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# HG changeset patch
# User Olaf Hering <olaf@aepfle.de>
# Date 1323189150 -3600
# Node ID 4e52b9c9309815a4b05c7b970a95e318d59fb71b
# Parent 7f2cfd9bd113c40a49cc7e036fd07eb706a22f15
xenpaging: restore p2mt if gfn is needed before evict

In the rare case that a gfn is needed by a guest or a foreign domain
between nominate and evict, restore the p2mt and skip sending a request.
A request is not needed because the pager will notice the evict failure.

Signed-off-by: Olaf Hering <olaf@aepfle.de>

diff -r 7f2cfd9bd113 -r 4e52b9c93098 xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -905,6 +905,7 @@ void p2m_mem_paging_populate(struct doma
p2m_type_t p2mt;
p2m_access_t a;
mfn_t mfn;
+ int restored = 0;
struct p2m_domain *p2m = p2m_get_hostp2m(d);

/* Check that there's space on the ring for this request */
@@ -920,22 +921,25 @@ void p2m_mem_paging_populate(struct doma
/* Allow only nominated or evicted pages to enter page-in path */
if ( p2m_do_populate(p2mt) )
{
- /* Evict will fail now, tag this request for pager */
- if ( p2mt == p2m_ram_paging_out )
- req.flags |= MEM_EVENT_FLAG_EVICT_FAIL;
-
- set_p2m_entry(p2m, gfn, mfn, PAGE_ORDER_4K, p2m_ram_paging_in_start, a);
+ /* Restore page state if gfn was requested before evict */
+ if ( p2mt == p2m_ram_paging_out && mfn_valid(mfn) ) {
+ set_p2m_entry(p2m, gfn, mfn, PAGE_ORDER_4K,
+ paging_mode_log_dirty(d) ? p2m_ram_logdirty : p2m_ram_rw, a);
+ restored = 1;
+ } else {
+ set_p2m_entry(p2m, gfn, mfn, PAGE_ORDER_4K, p2m_ram_paging_in_start, a);
+ }
}
p2m_unlock(p2m);

/* Pause domain if request came from guest and gfn has paging type */
- if ( p2m_is_paging(p2mt) && v->domain == d )
+ if ( !restored && p2m_is_paging(p2mt) && v->domain == d )
{
vcpu_pause_nosync(v);
req.flags |= MEM_EVENT_FLAG_VCPU_PAUSED;
}
/* No need to inform pager if the gfn is not in the page-out path */
- else if ( !p2m_do_populate(p2mt) )
+ else if ( restored || !p2m_do_populate(p2mt) )
{
/* gfn is already on its way back and vcpu is not paused */
mem_event_put_req_producers(&d->mem_event->paging);

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