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From 426a8346c01075ec5eba4aadefab03a96b6ece6a Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich@suse.com>
Date: Mon, 31 Oct 2022 13:26:33 +0100
Subject: [PATCH 39/87] common: map_vcpu_info() wants to unshare the underlying
page
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Not passing P2M_UNSHARE to get_page_from_gfn() means there won't even be
an attempt to unshare the referenced page, without any indication to the
caller (e.g. -EAGAIN). Note that guests have no direct control over
which of their pages are shared (or paged out), and hence they have no
way to make sure all on their own that the subsequent obtaining of a
writable type reference can actually succeed.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Julien Grall <jgrall@amazon.com>
master commit: 48980cf24d5cf41fd644600f99c753419505e735
master date: 2022-10-28 11:38:32 +0200
---
xen/common/domain.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 56d47dd66478..e3afcacb6cae 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1471,7 +1471,7 @@ int map_vcpu_info(struct vcpu *v, unsigned long gfn, unsigned offset)
if ( (v != current) && !(v->pause_flags & VPF_down) )
return -EINVAL;
- page = get_page_from_gfn(d, gfn, NULL, P2M_ALLOC);
+ page = get_page_from_gfn(d, gfn, NULL, P2M_UNSHARE);
if ( !page )
return -EINVAL;
--
2.37.4
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