[Xen-devel] [PATCH v2] x86/ept: pass correct level to p2m_entry_modify

Roger Pau Monne posted 1 patch 16 weeks ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/xen tags/patchew/20190703113326.2344-1-roger.pau@citrix.com
xen/arch/x86/mm/p2m-ept.c | 2 +-
xen/include/asm-x86/p2m.h | 1 +
2 files changed, 2 insertions(+), 1 deletion(-)

[Xen-devel] [PATCH v2] x86/ept: pass correct level to p2m_entry_modify

Posted by Roger Pau Monne 16 weeks ago
EPT differs from NPT and shadow when translating page orders to levels
in the physmap page tables. EPT page tables level for order 0 pages is
0, while NPT and shadow instead use 1, ie: EPT page tables levels
starts at 0 while NPT and shadow starts at 1.

Fix the p2m_entry_modify call in atomic_write_ept_entry to always add
one to the level, in order to match NPT and shadow usage.

While there also add a check to ensure p2m_entry_modify is never
called with level == 0. That should allow to catch future errors
related to the level parameter.

Fixes: c7a4c088ad1c ('x86/mm: split p2m ioreq server pages special handling into helper')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Cc: Jun Nakajima <jun.nakajima@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: George Dunlap <george.dunlap@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Wei Liu <wl@xen.org>
---
Changes since v1:
 - Check level is != 0 in p2m_entry_modify.
 - Expand digits of hash id.
---
 xen/arch/x86/mm/p2m-ept.c | 2 +-
 xen/include/asm-x86/p2m.h | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index e3044bee2e..6b8468c793 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -51,7 +51,7 @@ static int atomic_write_ept_entry(struct p2m_domain *p2m,
                                   int level)
 {
     int rc = p2m_entry_modify(p2m, new.sa_p2mt, entryptr->sa_p2mt,
-                              _mfn(new.mfn), _mfn(entryptr->mfn), level);
+                              _mfn(new.mfn), _mfn(entryptr->mfn), level + 1);
 
     if ( rc )
         return rc;
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 09ef7e02fd..aff34e3adf 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -946,6 +946,7 @@ static inline int p2m_entry_modify(struct p2m_domain *p2m, p2m_type_t nt,
                                    p2m_type_t ot, mfn_t nfn, mfn_t ofn,
                                    unsigned int level)
 {
+    BUG_ON(!level);
     BUG_ON(level > 1 && (nt == p2m_ioreq_server || nt == p2m_map_foreign));
 
     if ( level != 1 || (nt == ot && mfn_eq(nfn, ofn)) )
-- 
2.20.1 (Apple Git-117)


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Re: [Xen-devel] [PATCH v2] x86/ept: pass correct level to p2m_entry_modify

Posted by Tian, Kevin 15 weeks ago
> From: Roger Pau Monne [mailto:roger.pau@citrix.com]
> Sent: Wednesday, July 3, 2019 7:33 PM
> 
> EPT differs from NPT and shadow when translating page orders to levels
> in the physmap page tables. EPT page tables level for order 0 pages is
> 0, while NPT and shadow instead use 1, ie: EPT page tables levels
> starts at 0 while NPT and shadow starts at 1.
> 
> Fix the p2m_entry_modify call in atomic_write_ept_entry to always add
> one to the level, in order to match NPT and shadow usage.
> 
> While there also add a check to ensure p2m_entry_modify is never
> called with level == 0. That should allow to catch future errors
> related to the level parameter.
> 
> Fixes: c7a4c088ad1c ('x86/mm: split p2m ioreq server pages special handling
> into helper')
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
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Re: [Xen-devel] [PATCH v2] x86/ept: pass correct level to p2m_entry_modify

Posted by Jan Beulich 16 weeks ago
On 03.07.2019 13:33, Roger Pau Monne wrote:
> EPT differs from NPT and shadow when translating page orders to levels
> in the physmap page tables. EPT page tables level for order 0 pages is
> 0, while NPT and shadow instead use 1, ie: EPT page tables levels
> starts at 0 while NPT and shadow starts at 1.
> 
> Fix the p2m_entry_modify call in atomic_write_ept_entry to always add
> one to the level, in order to match NPT and shadow usage.
> 
> While there also add a check to ensure p2m_entry_modify is never
> called with level == 0. That should allow to catch future errors
> related to the level parameter.
> 
> Fixes: c7a4c088ad1c ('x86/mm: split p2m ioreq server pages special handling into helper')
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>

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