Re: [PATCH v4 01/17] x86/common: Align cpu_caps_cleared and cpu_caps_set to unsigned long

Paolo Bonzini
2019-03-04T13:13:18Z

On 04/03/19 13:44, Peter Zijlstra wrote:
> On Mon, Mar 04, 2019 at 11:48:18AM +0100, Paolo Bonzini wrote:
>> True that. On the other hand btsl/btrl is also one byte smaller if no
>> operand is %r8-%r15.
>
> Because then we loose the REX prefix, right. Now _that_ might actually
> be a reason to do that :-)

I knew that would be the right way to put it for you. :)

>> In any case, /me wonders if we should have a macro like
>>
>> #define DECLARE_LE_BITMAP(name,bits) \
>> u32 name[DIV_ROUND_UP(bits, 32)] __aligned(sizeof(unsigned long))
>
> s/u32/__le32/
>
> To go in bitops/le.h, sure, if there's enough users.

Hmm... actually that should be "BITS_TO_LONGS(bits) * sizeof(unsigned
long) / 4" because bitmap functions may access (or even clear) the last
word as 64 bits.

Paolo