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From 317894fa6a067a7903199bc5c1e3e06a0436caf8 Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich@suse.com>
Date: Mon, 31 Oct 2022 13:36:50 +0100
Subject: [PATCH 079/126] 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 17cc32fde373..0fb7f9a6225c 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1454,7 +1454,7 @@ 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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