From: Anton Ivanov <anton.ivanov@cambridgegreys.com>
To: Johannes Berg <johannes@sipsolutions.net>, linux-um@lists.infradead.org
Cc: richard@nod.at
Subject: Re: [PATCH v7] um: Enable preemption in UML
Date: Thu, 28 Mar 2024 14:40:06 +0000 [thread overview]
Message-ID: <8fadcc0e-2587-4628-bfb9-8794ef01cac3@cambridgegreys.com> (raw)
In-Reply-To: <4ffdc415c692236dc13302b5fc0290316a17b7cc.camel@sipsolutions.net>
On 28/03/2024 09:27, Johannes Berg wrote:
>
>> @@ -23,7 +23,7 @@ struct thread_info {
>> int preempt_count; /* 0 => preemptable,
>> <0 => BUG */
>> struct thread_info *real_thread; /* Points to non-IRQ stack */
>> - unsigned long aux_fp_regs[FP_SIZE]; /* auxiliary fp_regs to save/restore
>> + unsigned long aux_fp_regs[FP_SIZE] __aligned(64); /* auxiliary fp_regs to save/restore
>> them out-of-band */
>
> nit: that comment looks strange now, maybe pull it up before the member?
>
> /* auxiliary ... out-of-band */
> unsigned long aux_fp_regs[...] __aligned(64);
>
Ack.
>
>> +#ifdef CONFIG_64BIT
>> + if (likely(cpu_has(&boot_cpu_data, X86_FEATURE_XSAVEOPT)))
>> + __builtin_ia32_xsaveopt64(¤t_thread_info()->aux_fp_regs, KNOWN_387_FEATURES);
>> + else {
>> + if (likely(cpu_has(&boot_cpu_data, X86_FEATURE_XSAVE)))
>> + __builtin_ia32_xsave64(¤t_thread_info()->aux_fp_regs, KNOWN_387_FEATURES);
>> + else
>> + __builtin_ia32_fxsave64(¤t_thread_info()->aux_fp_regs);
>> + }
>
> Why not write this as a chain?
>
> if (likely(cpu_has(...))
> __builtin_ia32_xsaveopt64(...);
> else if (likely(cpu_has(...)))
> __builtin_ia32_xave64(...);
> else
> __builtin_ia32_fxsave64(...);
>
>
> and IMHO pulling the "¤t_thread_info()->aux_fp_regs" that appears
> on all three of them into a local variable would make that more readable
> too.
Ack.
>
>> +#else
>> + if (likely(cpu_has(&boot_cpu_data, X86_FEATURE_XSAVEOPT)))
>> + __builtin_ia32_xsaveopt(¤t->aux_fp_regs, KNOWN_387_FEATURES);
>> + else {
>> + if (likely(cpu_has(&boot_cpu_data, X86_FEATURE_XSAVE)))
>> + __builtin_ia32_xsave(¤t->aux_fp_regs, KNOWN_387_FEATURES);
>> + else
>> + __builtin_ia32_fxsave(¤t->aux_fp_regs);
>> + }
>> +#endif
>
> And all of the above also applies for 32-bit,
Ack.
>
>> +void kernel_fpu_end(void)
>
> and this as well.
>
> johannes
>
>
Will fix, rebase, retest and resubmit.
--
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/
prev parent reply other threads:[~2024-03-28 14:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-28 9:10 [PATCH v7] um: Enable preemption in UML anton.ivanov
2023-09-28 9:12 ` Anton Ivanov
2024-03-28 9:27 ` Johannes Berg
2024-03-28 14:40 ` Anton Ivanov [this message]
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