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Jan Beulich

2009-Jul-17 09:20 UTC

[Xen-devel] [PATCH] x86: moke show_page_walk() more robust

This should fix the host crash reported in the thread "d273:v3: 
reserved bit in page table (ec=0019)" (but it specifically doesn''t
deal
with the yet unknown original cause of the problem).

Also add in a missing line in x86-64''s do_page_walk().

Signed-off-by: Jan Beulich <jbeulich@novell.com>

--- 2009-07-10.orig/xen/arch/x86/x86_32/traps.c	2009-07-10 13:58:56.000000000
+0200
+++ 2009-07-10/xen/arch/x86/x86_32/traps.c	2009-07-17 11:12:42.000000000 +0200
@@ -165,7 +165,8 @@ void show_page_walk(unsigned long addr)
     printk(" L3[0x%03lx] = %"PRIpte" %08lx\n",
            l3_table_offset(addr), l3e_get_intpte(l3e), pfn);
     unmap_domain_page(l3t);
-    if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) )
+    if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) ||
+         !mfn_valid(mfn) )
         return;
 
     l2t = map_domain_page(mfn);
@@ -178,7 +179,8 @@ void show_page_walk(unsigned long addr)
            (l2e_get_flags(l2e) & _PAGE_PSE) ? "(PSE)" :
"");
     unmap_domain_page(l2t);
     if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ||
-         (l2e_get_flags(l2e) & _PAGE_PSE) )
+         (l2e_get_flags(l2e) & _PAGE_PSE) ||
+         !mfn_valid(mfn) )
         return;
 
     l1t = map_domain_page(mfn);
--- 2009-07-10.orig/xen/arch/x86/x86_64/mm.c	2009-07-10 13:58:56.000000000 +0200
+++ 2009-07-10/xen/arch/x86/x86_64/mm.c	2009-07-17 11:10:29.000000000 +0200
@@ -124,6 +124,7 @@ void *do_page_walk(struct vcpu *v, unsig
     l3e = l3t[l3_table_offset(addr)];
     mfn = l3e_get_pfn(l3e);
     if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) || !mfn_valid(mfn) )
+        return NULL;
     if ( (l3e_get_flags(l3e) & _PAGE_PSE) )
         return mfn_to_virt(mfn) + (addr & ((1UL <<
L3_PAGETABLE_SHIFT) - 1));
 
--- 2009-07-10.orig/xen/arch/x86/x86_64/traps.c	2009-07-10 13:58:56.000000000
+0200
+++ 2009-07-10/xen/arch/x86/x86_64/traps.c	2009-07-17 11:11:59.000000000 +0200
@@ -180,7 +180,8 @@ void show_page_walk(unsigned long addr)
     pfn = mfn_valid(mfn) ? get_gpfn_from_mfn(mfn) : INVALID_M2P_ENTRY;
     printk(" L4[0x%03lx] = %"PRIpte" %016lx\n",
            l4_table_offset(addr), l4e_get_intpte(l4e), pfn);
-    if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) )
+    if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) ||
+         !mfn_valid(mfn) )
         return;
 
     l3t = mfn_to_virt(mfn);
@@ -192,7 +193,8 @@ void show_page_walk(unsigned long addr)
            l3_table_offset(addr), l3e_get_intpte(l3e), pfn,
            (l3e_get_flags(l3e) & _PAGE_PSE) ? " (PSE)" :
"");
     if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) ||
-         (l3e_get_flags(l3e) & _PAGE_PSE) )
+         (l3e_get_flags(l3e) & _PAGE_PSE) ||
+         !mfn_valid(mfn) )
         return;
 
     l2t = mfn_to_virt(mfn);
@@ -204,7 +206,8 @@ void show_page_walk(unsigned long addr)
            l2_table_offset(addr), l2e_get_intpte(l2e), pfn,
            (l2e_get_flags(l2e) & _PAGE_PSE) ? "(PSE)" :
"");
     if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ||
-         (l2e_get_flags(l2e) & _PAGE_PSE) )
+         (l2e_get_flags(l2e) & _PAGE_PSE) ||
+         !mfn_valid(mfn) )
         return;
 
     l1t = mfn_to_virt(mfn);




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Keir Fraser

2009-Jul-17 19:48 UTC

head link

Re: [Xen-devel] [PATCH] x86: moke show_page_walk() more robust

Is this worthwhile? It''s kind of game over by this point, and we
already
dumped out the useful stuff. And the ensuing crash makes it very clear that
the page walk discovered an invalid mfn (rather than this alternative of
silently truncating the walk).

 -- Keir

On 17/07/2009 10:20, "Jan Beulich" <JBeulich@novell.com> wrote:
> This should fix the host crash reported in the thread "d273:v3:
> reserved bit in page table (ec=0019)" (but it specifically
doesn''t deal
> with the yet unknown original cause of the problem).
> 
> Also add in a missing line in x86-64''s do_page_walk().
> 
> Signed-off-by: Jan Beulich <jbeulich@novell.com>
> 
> --- 2009-07-10.orig/xen/arch/x86/x86_32/traps.c 2009-07-10
13:58:56.000000000
> +0200
> +++ 2009-07-10/xen/arch/x86/x86_32/traps.c 2009-07-17 11:12:42.000000000
+0200
> @@ -165,7 +165,8 @@ void show_page_walk(unsigned long addr)
>      printk(" L3[0x%03lx] = %"PRIpte" %08lx\n",
>             l3_table_offset(addr), l3e_get_intpte(l3e), pfn);
>      unmap_domain_page(l3t);
> -    if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) )
> +    if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) ||
> +         !mfn_valid(mfn) )
>          return;
>  
>      l2t = map_domain_page(mfn);
> @@ -178,7 +179,8 @@ void show_page_walk(unsigned long addr)
>             (l2e_get_flags(l2e) & _PAGE_PSE) ? "(PSE)" :
"");
>      unmap_domain_page(l2t);
>      if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ||
> -         (l2e_get_flags(l2e) & _PAGE_PSE) )
> +         (l2e_get_flags(l2e) & _PAGE_PSE) ||
> +         !mfn_valid(mfn) )
>          return;
>  
>      l1t = map_domain_page(mfn);
> --- 2009-07-10.orig/xen/arch/x86/x86_64/mm.c 2009-07-10 13:58:56.000000000
> +0200
> +++ 2009-07-10/xen/arch/x86/x86_64/mm.c 2009-07-17 11:10:29.000000000 +0200
> @@ -124,6 +124,7 @@ void *do_page_walk(struct vcpu *v, unsig
>      l3e = l3t[l3_table_offset(addr)];
>      mfn = l3e_get_pfn(l3e);
>      if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) || !mfn_valid(mfn) )
> +        return NULL;
>      if ( (l3e_get_flags(l3e) & _PAGE_PSE) )
>          return mfn_to_virt(mfn) + (addr & ((1UL <<
L3_PAGETABLE_SHIFT) - 1));
>  
> --- 2009-07-10.orig/xen/arch/x86/x86_64/traps.c 2009-07-10
13:58:56.000000000
> +0200
> +++ 2009-07-10/xen/arch/x86/x86_64/traps.c 2009-07-17 11:11:59.000000000
+0200
> @@ -180,7 +180,8 @@ void show_page_walk(unsigned long addr)
>      pfn = mfn_valid(mfn) ? get_gpfn_from_mfn(mfn) : INVALID_M2P_ENTRY;
>      printk(" L4[0x%03lx] = %"PRIpte" %016lx\n",
>             l4_table_offset(addr), l4e_get_intpte(l4e), pfn);
> -    if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) )
> +    if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) ||
> +         !mfn_valid(mfn) )
>          return;
>  
>      l3t = mfn_to_virt(mfn);
> @@ -192,7 +193,8 @@ void show_page_walk(unsigned long addr)
>             l3_table_offset(addr), l3e_get_intpte(l3e), pfn,
>             (l3e_get_flags(l3e) & _PAGE_PSE) ? " (PSE)" :
"");
>      if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) ||
> -         (l3e_get_flags(l3e) & _PAGE_PSE) )
> +         (l3e_get_flags(l3e) & _PAGE_PSE) ||
> +         !mfn_valid(mfn) )
>          return;
>  
>      l2t = mfn_to_virt(mfn);
> @@ -204,7 +206,8 @@ void show_page_walk(unsigned long addr)
>             l2_table_offset(addr), l2e_get_intpte(l2e), pfn,
>             (l2e_get_flags(l2e) & _PAGE_PSE) ? "(PSE)" :
"");
>      if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ||
> -         (l2e_get_flags(l2e) & _PAGE_PSE) )
> +         (l2e_get_flags(l2e) & _PAGE_PSE) ||
> +         !mfn_valid(mfn) )
>          return;
>  
>      l1t = mfn_to_virt(mfn);
> 
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel


_______________________________________________
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Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

Jan Beulich

2009-Jul-20 06:39 UTC

head link

Re: [Xen-devel] [PATCH] x86: moke show_page_walk() more robust

I very much think it is worthwhile: In the case given, a supposed guest crash
resulted in a host crash - the expected behavior would have been to do the
page table walk, then forward the fault to the guest.

Jan
>>> Keir Fraser <keir.fraser@eu.citrix.com> 17.07.09 21:48
>>>Is this worthwhile? It''s kind of game over by this point, and we
already
dumped out the useful stuff. And the ensuing crash makes it very clear that
the page walk discovered an invalid mfn (rather than this alternative of
silently truncating the walk).

 -- Keir

On 17/07/2009 10:20, "Jan Beulich" <JBeulich@novell.com> wrote:
> This should fix the host crash reported in the thread "d273:v3:
> reserved bit in page table (ec=0019)" (but it specifically
doesn''t deal
> with the yet unknown original cause of the problem).
> 
> Also add in a missing line in x86-64''s do_page_walk().
> 
> Signed-off-by: Jan Beulich <jbeulich@novell.com>
> 
> --- 2009-07-10.orig/xen/arch/x86/x86_32/traps.c 2009-07-10
13:58:56.000000000
> +0200
> +++ 2009-07-10/xen/arch/x86/x86_32/traps.c 2009-07-17 11:12:42.000000000
+0200
> @@ -165,7 +165,8 @@ void show_page_walk(unsigned long addr)
>      printk(" L3[0x%03lx] = %"PRIpte" %08lx\n",
>             l3_table_offset(addr), l3e_get_intpte(l3e), pfn);
>      unmap_domain_page(l3t);
> -    if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) )
> +    if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) ||
> +         !mfn_valid(mfn) )
>          return;
>  
>      l2t = map_domain_page(mfn);
> @@ -178,7 +179,8 @@ void show_page_walk(unsigned long addr)
>             (l2e_get_flags(l2e) & _PAGE_PSE) ? "(PSE)" :
"");
>      unmap_domain_page(l2t);
>      if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ||
> -         (l2e_get_flags(l2e) & _PAGE_PSE) )
> +         (l2e_get_flags(l2e) & _PAGE_PSE) ||
> +         !mfn_valid(mfn) )
>          return;
>  
>      l1t = map_domain_page(mfn);
> --- 2009-07-10.orig/xen/arch/x86/x86_64/mm.c 2009-07-10 13:58:56.000000000
> +0200
> +++ 2009-07-10/xen/arch/x86/x86_64/mm.c 2009-07-17 11:10:29.000000000 +0200
> @@ -124,6 +124,7 @@ void *do_page_walk(struct vcpu *v, unsig
>      l3e = l3t[l3_table_offset(addr)];
>      mfn = l3e_get_pfn(l3e);
>      if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) || !mfn_valid(mfn) )
> +        return NULL;
>      if ( (l3e_get_flags(l3e) & _PAGE_PSE) )
>          return mfn_to_virt(mfn) + (addr & ((1UL <<
L3_PAGETABLE_SHIFT) - 1));
>  
> --- 2009-07-10.orig/xen/arch/x86/x86_64/traps.c 2009-07-10
13:58:56.000000000
> +0200
> +++ 2009-07-10/xen/arch/x86/x86_64/traps.c 2009-07-17 11:11:59.000000000
+0200
> @@ -180,7 +180,8 @@ void show_page_walk(unsigned long addr)
>      pfn = mfn_valid(mfn) ? get_gpfn_from_mfn(mfn) : INVALID_M2P_ENTRY;
>      printk(" L4[0x%03lx] = %"PRIpte" %016lx\n",
>             l4_table_offset(addr), l4e_get_intpte(l4e), pfn);
> -    if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) )
> +    if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) ||
> +         !mfn_valid(mfn) )
>          return;
>  
>      l3t = mfn_to_virt(mfn);
> @@ -192,7 +193,8 @@ void show_page_walk(unsigned long addr)
>             l3_table_offset(addr), l3e_get_intpte(l3e), pfn,
>             (l3e_get_flags(l3e) & _PAGE_PSE) ? " (PSE)" :
"");
>      if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) ||
> -         (l3e_get_flags(l3e) & _PAGE_PSE) )
> +         (l3e_get_flags(l3e) & _PAGE_PSE) ||
> +         !mfn_valid(mfn) )
>          return;
>  
>      l2t = mfn_to_virt(mfn);
> @@ -204,7 +206,8 @@ void show_page_walk(unsigned long addr)
>             l2_table_offset(addr), l2e_get_intpte(l2e), pfn,
>             (l2e_get_flags(l2e) & _PAGE_PSE) ? "(PSE)" :
"");
>      if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ||
> -         (l2e_get_flags(l2e) & _PAGE_PSE) )
> +         (l2e_get_flags(l2e) & _PAGE_PSE) ||
> +         !mfn_valid(mfn) )
>          return;
>  
>      l1t = mfn_to_virt(mfn);
> 
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com 
> http://lists.xensource.com/xen-devel 


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

Keir Fraser

2009-Jul-20 07:06 UTC

head link

Re: [Xen-devel] [PATCH] x86: moke show_page_walk() more robust

It''s not merely a guest crash. It shouldn''t be possible for a
guest to end
up with bogus PTEs. It''s a host consistency issue and hence a host
crash is
appropriate.

 -- Keir

On 20/07/2009 07:39, "Jan Beulich" <JBeulich@novell.com> wrote:
> I very much think it is worthwhile: In the case given, a supposed guest
crash
> resulted in a host crash - the expected behavior would have been to do the
> page table walk, then forward the fault to the guest.
> 
> Jan
> 
>>>> Keir Fraser <keir.fraser@eu.citrix.com> 17.07.09 21:48
>>>
> Is this worthwhile? It''s kind of game over by this point, and we
already
> dumped out the useful stuff. And the ensuing crash makes it very clear that
> the page walk discovered an invalid mfn (rather than this alternative of
> silently truncating the walk).
> 
>  -- Keir
> 
> On 17/07/2009 10:20, "Jan Beulich" <JBeulich@novell.com>
wrote:
> 
>> This should fix the host crash reported in the thread "d273:v3:
>> reserved bit in page table (ec=0019)" (but it specifically
doesn''t deal
>> with the yet unknown original cause of the problem).
>> 
>> Also add in a missing line in x86-64''s do_page_walk().
>> 
>> Signed-off-by: Jan Beulich <jbeulich@novell.com>
>> 
>> --- 2009-07-10.orig/xen/arch/x86/x86_32/traps.c 2009-07-10
13:58:56.000000000
>> +0200
>> +++ 2009-07-10/xen/arch/x86/x86_32/traps.c 2009-07-17
11:12:42.000000000
>> +0200
>> @@ -165,7 +165,8 @@ void show_page_walk(unsigned long addr)
>>      printk(" L3[0x%03lx] = %"PRIpte" %08lx\n",
>>             l3_table_offset(addr), l3e_get_intpte(l3e), pfn);
>>      unmap_domain_page(l3t);
>> -    if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) )
>> +    if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) ||
>> +         !mfn_valid(mfn) )
>>          return;
>>  
>>      l2t = map_domain_page(mfn);
>> @@ -178,7 +179,8 @@ void show_page_walk(unsigned long addr)
>>             (l2e_get_flags(l2e) & _PAGE_PSE) ? "(PSE)" :
"");
>>      unmap_domain_page(l2t);
>>      if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ||
>> -         (l2e_get_flags(l2e) & _PAGE_PSE) )
>> +         (l2e_get_flags(l2e) & _PAGE_PSE) ||
>> +         !mfn_valid(mfn) )
>>          return;
>>  
>>      l1t = map_domain_page(mfn);
>> --- 2009-07-10.orig/xen/arch/x86/x86_64/mm.c 2009-07-10
13:58:56.000000000
>> +0200
>> +++ 2009-07-10/xen/arch/x86/x86_64/mm.c 2009-07-17 11:10:29.000000000
+0200
>> @@ -124,6 +124,7 @@ void *do_page_walk(struct vcpu *v, unsig
>>      l3e = l3t[l3_table_offset(addr)];
>>      mfn = l3e_get_pfn(l3e);
>>      if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) || !mfn_valid(mfn)
)
>> +        return NULL;
>>      if ( (l3e_get_flags(l3e) & _PAGE_PSE) )
>>          return mfn_to_virt(mfn) + (addr & ((1UL <<
L3_PAGETABLE_SHIFT) -
>> 1));
>>  
>> --- 2009-07-10.orig/xen/arch/x86/x86_64/traps.c 2009-07-10
13:58:56.000000000
>> +0200
>> +++ 2009-07-10/xen/arch/x86/x86_64/traps.c 2009-07-17
11:11:59.000000000
>> +0200
>> @@ -180,7 +180,8 @@ void show_page_walk(unsigned long addr)
>>      pfn = mfn_valid(mfn) ? get_gpfn_from_mfn(mfn) : INVALID_M2P_ENTRY;
>>      printk(" L4[0x%03lx] = %"PRIpte" %016lx\n",
>>             l4_table_offset(addr), l4e_get_intpte(l4e), pfn);
>> -    if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) )
>> +    if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) ||
>> +         !mfn_valid(mfn) )
>>          return;
>>  
>>      l3t = mfn_to_virt(mfn);
>> @@ -192,7 +193,8 @@ void show_page_walk(unsigned long addr)
>>             l3_table_offset(addr), l3e_get_intpte(l3e), pfn,
>>             (l3e_get_flags(l3e) & _PAGE_PSE) ? " (PSE)" :
"");
>>      if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) ||
>> -         (l3e_get_flags(l3e) & _PAGE_PSE) )
>> +         (l3e_get_flags(l3e) & _PAGE_PSE) ||
>> +         !mfn_valid(mfn) )
>>          return;
>>  
>>      l2t = mfn_to_virt(mfn);
>> @@ -204,7 +206,8 @@ void show_page_walk(unsigned long addr)
>>             l2_table_offset(addr), l2e_get_intpte(l2e), pfn,
>>             (l2e_get_flags(l2e) & _PAGE_PSE) ? "(PSE)" :
"");
>>      if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ||
>> -         (l2e_get_flags(l2e) & _PAGE_PSE) )
>> +         (l2e_get_flags(l2e) & _PAGE_PSE) ||
>> +         !mfn_valid(mfn) )
>>          return;
>>  
>>      l1t = mfn_to_virt(mfn);
>> 
>> 
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xensource.com
>> http://lists.xensource.com/xen-devel
> 
> 


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Xen devel - Jul 2009 - [PATCH] x86: moke show_page_walk() more robust

[Xen-devel] [PATCH] x86: moke show_page_walk() more robust

Re: [Xen-devel] [PATCH] x86: moke show_page_walk() more robust

Re: [Xen-devel] [PATCH] x86: moke show_page_walk() more robust

Re: [Xen-devel] [PATCH] x86: moke show_page_walk() more robust