On Oct 1, 2021, at 05:45, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> On Wed, Aug 25 2021 at 08:53, Chang S. Bae wrote:
>> Have the function initializing the XSTATE buffer take a struct fpu *
>> pointer in preparation for dynamic state buffer support.
>>
>> init_fpstate is a special case, which is indicated by a null pointer
>> parameter to fpstate_init().
>>
>> Also, fpstate_init_xstate() now accepts the state component bitmap to
>> customize the compacted format.
>
> That's not a changelog. Changelogs have to explain the WHY not the WHAT.
>
> I can see the WHY when I look at the later changes, but that's not how
> it works.
The same feedback was raised before [1]. I thought this changelog has been
settled down with Boris [2].
How about:
“To prepare dynamic features, change fpstate_init()’s argument to a struct
fpu * pointer instead of a struct fpregs_state * pointer. A struct fpu
will have new fields to handle dynamic features."
With fpstate_init_xstate() changes in a separate patch and defining init_fpu,
the last two sentences shall be removed.
> Also the subject of this patch is just wrong. It does not make the
> functions handle dynamic buffers, it prepares them to add support for
> that later.
How about “Prepare fpstate_init() to handle dynamic features"
>> +static inline void fpstate_init_xstate(struct xregs_state *xsave, u64 mask)
>> +{
>> + /*
>> + * XRSTORS requires these bits set in xcomp_bv, or it will
>> + * trigger #GP:
>> + */
>> + xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | mask;
>> +}
>
> This wants to be a separate cleanup patch which replaces the open coded
> variant here:
Okay, maybe the change becomes to be the new patch1.
>> diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
>> index fc1d529547e6..0fed7fbcf2e8 100644
>> --- a/arch/x86/kernel/fpu/xstate.c
>> +++ b/arch/x86/kernel/fpu/xstate.c
>> @@ -395,8 +395,7 @@ static void __init setup_init_fpu_buf(void)
>> print_xstate_features();
>>
>> if (boot_cpu_has(X86_FEATURE_XSAVES))
>> - init_fpstate.xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
>> - xfeatures_mask_all;
>> + fpstate_init_xstate(&init_fpstate.xsave, xfeatures_mask_all);
Thanks,
Chang
[1] https://lore.kernel.org/lkml/20201207171251.GB16640@xxxxxxx/
[2] https://lore.kernel.org/lkml/20210115124038.GA11337@xxxxxxx/
