Re: [Xen-devel] [PATCH RFC 4/7] xen/x86: Migrate to XBI structure

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.09.14 at 15:22, <daniel.kiper@xxxxxxxxxx> wrote:
> On Sun, Aug 10, 2014 at 06:05:38PM +0100, Andrew Cooper wrote:
>> On 09/08/14 00:04, Daniel Kiper wrote:
>> > +static void zero_struct(u32 s, u32 bytes)
>> > +{
>> > +    asm volatile(
>> > +    "    cld                          \n"
>>
>> __start has already performed cld for us.  There is nothing which will
>> have set it between then and here.
> 
> Hmmm... Are we sure that gcc will not insert an instruction
> which will change direction flag? cld does not cost a lot
> and we will be on safe side here.

Just consider in how many other places we'd need CLD if gcc was
permitted to play freely with EFLAGS.DF.

Jan


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