Re: [Xen-devel] [PATCH] xen: make some constants usable for assembler

[Juergen Gross <jgross@xxxxxxxx>]

On 16/02/16 15:04, Jan Beulich wrote:
>>>> On 16.02.16 at 14:02, <JGross@xxxxxxxx> wrote:
>> Some constants defined in xen/include/public/xen.h are not usable in
>> assembler sources as they are either defined with "U" or "UL" suffixes
>> or they are inside #ifndef __ASSEMBLY__ areas.
>>
>> Change this as grub2 could make use of those definitions.
>>
>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>> ---
>>  xen/include/public/xen.h | 58 
>> ++++++++++++++++++++++++++----------------------
>>  1 file changed, 31 insertions(+), 27 deletions(-)
>>
>> diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
>> index 7b629b1..e29a12a 100644
>> --- a/xen/include/public/xen.h
>> +++ b/xen/include/public/xen.h
>> @@ -52,6 +52,19 @@ DEFINE_XEN_GUEST_HANDLE(void);
>>  DEFINE_XEN_GUEST_HANDLE(uint64_t);
>>  DEFINE_XEN_GUEST_HANDLE(xen_pfn_t);
>>  DEFINE_XEN_GUEST_HANDLE(xen_ulong_t);
>> +
>> +/* Turn a plain number into a C unsigned (long) constant. */
>> +#define __mk_unsigned(x)      x ## U
>> +#define __mk_unsigned_long(x) x ## UL
>> +#define mk_unsigned(x)        __mk_unsigned(x)
>> +#define mk_unsigned_long(x)   __mk_unsigned_long(x)
>> +
>> +#else
>> +
>> +/* In assembly code we cannot use C numeric constant suffixes. */
>> +#define mk_unsigned(x)      x
>> +#define mk_unsigned_long(x) x
>> +
>>  #endif
> 
> I realize that you're just moving up the mis-named
> mk_unsigned_long(). That alone I guess we'd have to tolerate, but
> since you also add another variant thereof, the name space issue
> needs fixing imo (even more so since they can't be #undef-d at the
> end of the header): Both should carry Xen in their name in some
> way. Maybe xen_mk_uint() and xen_mk_ulong()?

I'm fine with this.

> 
>> @@ -451,13 +464,13 @@ DEFINE_XEN_GUEST_HANDLE(mmuext_op_t);
>>  /* When specifying UVMF_MULTI, also OR in a pointer to a CPU bitmap.   */
>>  /* UVMF_LOCAL is merely UVMF_MULTI with a NULL bitmap pointer.         */
>>  /* ` enum uvm_flags { */
>> -#define UVMF_NONE               (0UL<<0) /* No flushing at all.   */
>> -#define UVMF_TLB_FLUSH          (1UL<<0) /* Flush entire TLB(s).  */
>> -#define UVMF_INVLPG             (2UL<<0) /* Flush only one entry. */
>> -#define UVMF_FLUSHTYPE_MASK     (3UL<<0)
>> -#define UVMF_MULTI              (0UL<<2) /* Flush subset of TLBs. */
>> -#define UVMF_LOCAL              (0UL<<2) /* Flush local TLB.      */
>> -#define UVMF_ALL                (1UL<<2) /* Flush all TLBs.       */
>> +#define UVMF_NONE            mk_unsigned_long(0<<0) /* No flushing at all.  
>>  */
>> +#define UVMF_TLB_FLUSH       mk_unsigned_long(1<<0) /* Flush entire TLB(s). 
>>  */
>> +#define UVMF_INVLPG          mk_unsigned_long(2<<0) /* Flush only one 
>> entry. */
>> +#define UVMF_FLUSHTYPE_MASK  mk_unsigned_long(3<<0)
>> +#define UVMF_MULTI           mk_unsigned_long(0<<2) /* Flush subset of 
>> TLBs. */
>> +#define UVMF_LOCAL           mk_unsigned_long(0<<2) /* Flush local TLB.     
>>  */
>> +#define UVMF_ALL             mk_unsigned_long(1<<2) /* Flush all TLBs.      
>>  */
> 
> These all look wrong - I think you mean
> 
> #define UVMF_ALL             (mk_unsigned_long(1)<<2)
> 
> etc, even if the difference is benign.

Oops, you are right. Sorry.

> 
>> @@ -504,15 +517,11 @@ DEFINE_XEN_GUEST_HANDLE(mmuext_op_t);
>>  #define MAX_VMASST_TYPE                  3
>>  #endif
>>  
>> -#ifndef __ASSEMBLY__
>> -
>> -typedef uint16_t domid_t;
>> -
>>  /* Domain ids >= DOMID_FIRST_RESERVED cannot be used for ordinary domains. 
>> */
>> -#define DOMID_FIRST_RESERVED (0x7FF0U)
>> +#define DOMID_FIRST_RESERVED mk_unsigned(0x7FF0)
>>  
>>  /* DOMID_SELF is used in certain contexts to refer to oneself. */
>> -#define DOMID_SELF (0x7FF0U)
>> +#define DOMID_SELF           mk_unsigned(0x7FF0)
>>  
>>  /*
>>   * DOMID_IO is used to restrict page-table updates to mapping I/O memory.
>> @@ -523,7 +532,7 @@ typedef uint16_t domid_t;
>>   * This only makes sense in MMUEXT_SET_FOREIGNDOM, but in that context can
>>   * be specified by any calling domain.
>>   */
>> -#define DOMID_IO   (0x7FF1U)
>> +#define DOMID_IO             mk_unsigned(0x7FF1)
>>  
>>  /*
>>   * DOMID_XEN is used to allow privileged domains to map restricted parts of
>> @@ -531,17 +540,21 @@ typedef uint16_t domid_t;
>>   * This only makes sense in MMUEXT_SET_FOREIGNDOM, and is only permitted if
>>   * the caller is privileged.
>>   */
>> -#define DOMID_XEN  (0x7FF2U)
>> +#define DOMID_XEN            mk_unsigned(0x7FF2)
>>  
>>  /*
>>   * DOMID_COW is used as the owner of sharable pages */
>> -#define DOMID_COW  (0x7FF3U)
>> +#define DOMID_COW            mk_unsigned(0x7FF3)
>>  
>>  /* DOMID_INVALID is used to identify pages with unknown owner. */
>> -#define DOMID_INVALID (0x7FF4U)
>> +#define DOMID_INVALID        mk_unsigned(0x7FF4)
>>  
>>  /* Idle domain. */
>> -#define DOMID_IDLE (0x7FFFU)
>> +#define DOMID_IDLE           mk_unsigned(0x7FFF)
>> +
>> +#ifndef __ASSEMBLY__
>> +
>> +typedef uint16_t domid_t;
> 
> It's hard to see why domain IDs would be needed in assembly code,
> but well ...

grub2 does: it is calling __HYPERVISOR_mmuext_op with DOMID_SELF from
assembly for activating the loaded kernel with it's new page tables.


Juergen


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