From: Dmitry Safonov <dima@arista.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org,
"Prasanna Panchamukhi" <panchamukhi@arista.com>,
"Andy Lutomirski" <luto@kernel.org>,
"Borislav Petkov" <bp@alien8.de>,
"Cathy Avery" <cavery@redhat.com>,
"Haiyang Zhang" <haiyangz@microsoft.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"Ingo Molnar" <mingo@redhat.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
"Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>,
"Mohammed Gamal" <mmorsy@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Roman Kagan" <rkagan@virtuozzo.com>,
"Sasha Levin" <sashal@kernel.org>,
"Stephen Hemminger" <sthemmin@microsoft.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
devel@linuxdriverproject.org, kvm@vger.kernel.org,
linux-hyperv@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH] x86/hyperv: Disable preemption while setting reenlightenment vector
Date: Fri, 14 Jun 2019 12:50:51 +0100 [thread overview]
Message-ID: <cb9e1645-98c2-4341-d6da-4effa4f57fb1@arista.com> (raw)
In-Reply-To: <877e9o7a4e.fsf@vitty.brq.redhat.com>
On 6/14/19 11:08 AM, Vitaly Kuznetsov wrote:
> Peter Zijlstra <peterz@infradead.org> writes:
>
>> @@ -182,7 +182,7 @@ void set_hv_tscchange_cb(void (*cb)(void))
>> struct hv_reenlightenment_control re_ctrl = {
>> .vector = HYPERV_REENLIGHTENMENT_VECTOR,
>> .enabled = 1,
>> - .target_vp = hv_vp_index[smp_processor_id()]
>> + .target_vp = hv_vp_index[raw_smp_processor_id()]
>> };
>> struct hv_tsc_emulation_control emu_ctrl = {.enabled = 1};
>>
>
> Yes, this should do, thanks! I'd also suggest to leave a comment like
> /*
> * This function can get preemted and migrate to a different CPU
> * but this doesn't matter. We just need to assign
> * reenlightenment notification to some online CPU. In case this
> * CPU goes offline, hv_cpu_die() will re-assign it to some
> * other online CPU.
> */
What if the cpu goes down just before wrmsrl()?
I mean, hv_cpu_die() will reassign another cpu, but this thread will be
resumed on some other cpu and will write cpu number which is at that
moment already down?
(probably I miss something)
And I presume it's guaranteed that during hv_cpu_die() no other cpu may
go down:
: new_cpu = cpumask_any_but(cpu_online_mask, cpu);
: re_ctrl.target_vp = hv_vp_index[new_cpu];
: wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
--
Dima
next prev parent reply other threads:[~2019-06-14 11:51 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-11 21:20 [PATCH] x86/hyperv: Disable preemption while setting reenlightenment vector Dmitry Safonov
2019-06-12 9:35 ` Peter Zijlstra
2019-06-12 10:25 ` Vitaly Kuznetsov
2019-06-12 10:17 ` Vitaly Kuznetsov
2019-06-13 19:00 ` Thomas Gleixner
2019-06-14 8:06 ` Vitaly Kuznetsov
2019-06-14 8:28 ` Peter Zijlstra
2019-06-14 10:08 ` Vitaly Kuznetsov
2019-06-14 11:50 ` Dmitry Safonov [this message]
2019-06-14 12:27 ` Peter Zijlstra
2019-06-14 14:28 ` Dmitry Safonov
2019-06-14 21:44 ` Vitaly Kuznetsov
2019-06-14 21:36 ` Vitaly Kuznetsov
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