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From d31385be5c8e8bc5efb6f8848057bd0c69e8274a Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich@suse.com>
Date: Wed, 26 Jun 2024 13:40:11 +0200
Subject: [PATCH 27/56] x86/EPT: avoid marking non-present entries for
re-configuring
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
For non-present entries EMT, like most other fields, is meaningless to
hardware. Make the logic in ept_set_entry() setting the field (and iPAT)
conditional upon dealing with a present entry, leaving the value at 0
otherwise. This has two effects for epte_get_entry_emt() which we'll
want to leverage subsequently:
1) The call moved here now won't be issued with INVALID_MFN anymore (a
respective BUG_ON() is being added).
2) Neither of the other two calls could now be issued with a truncated
form of INVALID_MFN anymore (as long as there's no bug anywhere
marking an entry present when that was populated using INVALID_MFN).
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
master commit: 777c71d31325bc55ba1cc3f317d4155fe519ab0b
master date: 2024-06-13 16:54:17 +0200
---
xen/arch/x86/mm/p2m-ept.c | 29 ++++++++++++++++++-----------
1 file changed, 18 insertions(+), 11 deletions(-)
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index 1aa6bbc771..641d61b350 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -649,6 +649,8 @@ static int cf_check resolve_misconfig(struct p2m_domain *p2m, unsigned long gfn)
if ( e.emt != MTRR_NUM_TYPES )
break;
+ ASSERT(is_epte_present(&e));
+
if ( level == 0 )
{
for ( gfn -= i, i = 0; i < EPT_PAGETABLE_ENTRIES; ++i )
@@ -914,17 +916,6 @@ ept_set_entry(struct p2m_domain *p2m, gfn_t gfn_, mfn_t mfn,
if ( mfn_valid(mfn) || p2m_allows_invalid_mfn(p2mt) )
{
- bool ipat;
- int emt = epte_get_entry_emt(p2m->domain, _gfn(gfn), mfn,
- i * EPT_TABLE_ORDER, &ipat,
- p2mt);
-
- if ( emt >= 0 )
- new_entry.emt = emt;
- else /* ept_handle_misconfig() will need to take care of this. */
- new_entry.emt = MTRR_NUM_TYPES;
-
- new_entry.ipat = ipat;
new_entry.sp = !!i;
new_entry.sa_p2mt = p2mt;
new_entry.access = p2ma;
@@ -940,6 +931,22 @@ ept_set_entry(struct p2m_domain *p2m, gfn_t gfn_, mfn_t mfn,
need_modify_vtd_table = 0;
ept_p2m_type_to_flags(p2m, &new_entry);
+
+ if ( is_epte_present(&new_entry) )
+ {
+ bool ipat;
+ int emt = epte_get_entry_emt(p2m->domain, _gfn(gfn), mfn,
+ i * EPT_TABLE_ORDER, &ipat,
+ p2mt);
+
+ BUG_ON(mfn_eq(mfn, INVALID_MFN));
+
+ if ( emt >= 0 )
+ new_entry.emt = emt;
+ else /* ept_handle_misconfig() will need to take care of this. */
+ new_entry.emt = MTRR_NUM_TYPES;
+ new_entry.ipat = ipat;
+ }
}
if ( sve != -1 )
--
2.45.2
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