From: "Liu, Jing2" <jing2.liu@linux.intel.com>
To: "Bae, Chang Seok" <chang.seok.bae@intel.com>
Cc: "Liu, Jing2" <jing2.liu@intel.com>, "bp@suse.de" <bp@suse.de>,
"luto@kernel.org" <luto@kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@kernel.org" <mingo@kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"Brown, Len" <len.brown@intel.com>,
"Hansen, Dave" <dave.hansen@intel.com>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH v3 10/21] x86/fpu/xstate: Update xstate save function to support dynamic xstate
Date: Fri, 15 Jan 2021 13:45:55 +0800 [thread overview]
Message-ID: <8178f22a-17bb-26c8-4a0b-4c459d5ef6bb@linux.intel.com> (raw)
In-Reply-To: <BFF7E955-B3BB-45A2-8A01-00ED8971C8D7@intel.com>
On 1/15/2021 12:59 PM, Bae, Chang Seok wrote:
>> On Jan 11, 2021, at 18:52, Liu, Jing2 <jing2.liu@linux.intel.com> wrote:
>>
>> On 1/8/2021 2:40 AM, Bae, Chang Seok wrote:
>>>> On Jan 7, 2021, at 17:41, Liu, Jing2 <jing2.liu@intel.com> wrote:
>>>>
>>>> static void kvm_save_current_fpu(struct fpu *fpu) {
>>>> + struct fpu *src_fpu = ¤t->thread.fpu;
>>>> +
>>>> /*
>>>> * If the target FPU state is not resident in the CPU registers, just
>>>> * memcpy() from current, else save CPU state directly to the target.
>>>> */
>>>> - if (test_thread_flag(TIF_NEED_FPU_LOAD))
>>>> - memcpy(&fpu->state, ¤t->thread.fpu.state,
>>>> + if (test_thread_flag(TIF_NEED_FPU_LOAD)) {
>>>> + memcpy(&fpu->state, &src_fpu->state,
>>>> fpu_kernel_xstate_min_size);
> <snip>
>
>>>> - else
>>>> + } else {
>>>> + if (fpu->state_mask != src_fpu->state_mask)
>>>> + fpu->state_mask = src_fpu->state_mask;
>>>>
>>>> Though dynamic feature is not supported in kvm now, this function still need
>>>> consider more things for fpu->state_mask.
>>> Can you elaborate this? Which path might be affected by fpu->state_mask
>>> without dynamic state supported in KVM?
>>>
>>>> I suggest that we can set it before if...else (for both cases) and not change other.
>>> I tried a minimum change here. The fpu->state_mask value does not impact the
>>> memcpy(). So, why do we need to change it for both?
>> Sure, what I'm considering is that "mask" is the first time introduced into "fpu",
>> representing the usage, so not only set it when needed, but also make it as a
>> representation, in case of anywhere using it (especially between the interval
>> of this series and kvm series in future).
> Thank you for the feedback. Sorry, I don't get any logical reason to set the
> mask always here.
Sure, I'd like to see if fx_init()->memset is the case,
though maybe no hurt so far in test.
Thanks,
Jing
> Perhaps, KVM code can be updated like you mentioned when
> supporting the dynamic states there.
>
> Please let me know if I’m missing any functional issues.
>
> Thanks,
> Chang
next prev parent reply other threads:[~2021-01-15 5:47 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201223155717.19556-1-chang.seok.bae@intel.com>
2020-12-23 15:56 ` [PATCH v3 01/21] x86/fpu/xstate: Modify initialization helper to handle both static and dynamic buffers Chang S. Bae
2021-01-15 12:40 ` Borislav Petkov
2020-12-23 15:56 ` [PATCH v3 03/21] x86/fpu/xstate: Modify address finders " Chang S. Bae
2021-01-15 13:06 ` Borislav Petkov
2020-12-23 15:57 ` [PATCH v3 04/21] x86/fpu/xstate: Modify context switch helpers " Chang S. Bae
2021-01-15 13:18 ` Borislav Petkov
2021-01-19 18:49 ` Bae, Chang Seok
2020-12-23 15:57 ` [PATCH v3 06/21] x86/fpu/xstate: Calculate and remember dynamic xstate buffer sizes Chang S. Bae
2021-01-22 11:44 ` Borislav Petkov
2021-01-27 1:23 ` Bae, Chang Seok
2021-01-27 9:38 ` Borislav Petkov
2021-02-03 2:54 ` Bae, Chang Seok
2020-12-23 15:57 ` [PATCH v3 10/21] x86/fpu/xstate: Update xstate save function to support dynamic xstate Chang S. Bae
2021-01-07 8:41 ` Liu, Jing2
2021-01-07 18:40 ` Bae, Chang Seok
2021-01-12 2:52 ` Liu, Jing2
2021-01-15 4:59 ` Bae, Chang Seok
2021-01-15 5:45 ` Liu, Jing2 [this message]
2021-02-08 12:33 ` Borislav Petkov
2021-02-09 15:48 ` Bae, Chang Seok
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