Re: [Xen-devel] [V3 PATCH 4/9] x86/hvm: pkeys, add functions to get pkeys value from PTE

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 10/12/15 15:48, George Dunlap wrote:
> On 07/12/15 09:16, Huaitong Han wrote:
>> This patch adds functions to get pkeys value from PTE.
>>
>> Signed-off-by: Huaitong Han <huaitong.han@xxxxxxxxx>
>> ---
>>  xen/include/asm-x86/guest_pt.h    |  7 +++++++
>>  xen/include/asm-x86/page.h        |  5 +++++
>>  xen/include/asm-x86/x86_64/page.h | 12 ++++++++++++
>>  3 files changed, 24 insertions(+)
>>
>> diff --git a/xen/include/asm-x86/guest_pt.h b/xen/include/asm-x86/guest_pt.h
>> index 3447973..6b0af70 100644
>> --- a/xen/include/asm-x86/guest_pt.h
>> +++ b/xen/include/asm-x86/guest_pt.h
>> @@ -154,6 +154,13 @@ static inline u32 guest_l4e_get_flags(guest_l4e_t gl4e)
>>  { return l4e_get_flags(gl4e); }
>>  #endif
>>  
>> +static inline u32 guest_l1e_get_pkeys(guest_l1e_t gl1e)
>> +{ return l1e_get_pkeys(gl1e); }
>> +static inline u32 guest_l2e_get_pkeys(guest_l2e_t gl2e)
>> +{ return l2e_get_pkeys(gl2e); }
>> +static inline u32 guest_l3e_get_pkeys(guest_l3e_t gl3e)
>> +{ return l3e_get_pkeys(gl3e); }
>> +
>>  static inline guest_l1e_t guest_l1e_from_gfn(gfn_t gfn, u32 flags)
>>  { return l1e_from_pfn(gfn_x(gfn), flags); }
>>  static inline guest_l2e_t guest_l2e_from_gfn(gfn_t gfn, u32 flags)
>> diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h
>> index a095a93..93a0db0 100644
>> --- a/xen/include/asm-x86/page.h
>> +++ b/xen/include/asm-x86/page.h
>> @@ -93,6 +93,11 @@
>>  #define l3e_get_flags(x)           (get_pte_flags((x).l3))
>>  #define l4e_get_flags(x)           (get_pte_flags((x).l4))
>>  
>> +/* Get pte pkeys (unsigned int). */
>> +#define l1e_get_pkeys(x)           (get_pte_pkeys((x).l1))
>> +#define l2e_get_pkeys(x)           (get_pte_pkeys((x).l2))
>> +#define l3e_get_pkeys(x)           (get_pte_pkeys((x).l3))
>> +
>>  /* Construct an empty pte. */
>>  #define l1e_empty()                ((l1_pgentry_t) { 0 })
>>  #define l2e_empty()                ((l2_pgentry_t) { 0 })
>> diff --git a/xen/include/asm-x86/x86_64/page.h 
>> b/xen/include/asm-x86/x86_64/page.h
>> index 19ab4d0..3ca489a 100644
>> --- a/xen/include/asm-x86/x86_64/page.h
>> +++ b/xen/include/asm-x86/x86_64/page.h
>> @@ -134,6 +134,18 @@ typedef l4_pgentry_t root_pgentry_t;
>>  #define get_pte_flags(x) (((int)((x) >> 40) & ~0xFFF) | ((int)(x) & 0xFFF))
>>  #define put_pte_flags(x) (((intpte_t)((x) & ~0xFFF) << 40) | ((x) & 0xFFF))
>>  
>> +/*
>> + * Protection keys define a new 4-bit protection key field
>> + * (PKEY) in bits 62:59 of leaf entries of the page tables.
>> + * This corresponds to bit 22:19 of a 24-bit flags.
>> + *
>> + * Notice: Bit 22 is used by _PAGE_GNTTAB which is visible to PV guests,
>> + * so Protection keys must be disabled on PV guests.
>> + */
>> +#define _PAGE_PKEY_BITS  (0x780000)  /* Protection Keys, 22:19 */
>> +
>> +#define get_pte_pkeys(x) (MASK_EXTR(get_pte_flags(x), _PAGE_PKEY_BITS))
> Sorry if I'm getting nit-picky here, but any given pte will only have a
> single pkey, right?  Would it be better if these were "get_pte_pkey()"
> (i.e., singular)?

Correct.  An individual pte contains 4 bits which is "the protection
key", an index (in the range 0-15) into the protection key register,
which ultimately determines access-denied/write-denied on the linear
address.

~Andrew

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel