Message-ID: <d0eeb5d0026ed0ecc12ea75b1e6cf03ee2ce068f.camel@infradead.org>
Subject: Re: [PATCH v7 5/9] x86/smpboot: Split up native_cpu_up into
 separate phases and document them
From:   David Woodhouse <dwmw2@infradead.org>
To:     Yuan Yao <yuan.yao@linux.intel.com>,
        Usama Arif <usama.arif@bytedance.com>
Cc:     tglx@linutronix.de, kim.phillips@amd.com, arjan@linux.intel.com,
        mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
        hpa@zytor.com, x86@kernel.org, pbonzini@redhat.com,
        paulmck@kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, rcu@vger.kernel.org, mimoja@mimoja.de,
        hewenliang4@huawei.com, thomas.lendacky@amd.com, seanjc@google.com,
        pmenzel@molgen.mpg.de, fam.zheng@bytedance.com,
        punit.agrawal@bytedance.com, simon.evans@bytedance.com,
        liangma@liangbit.com
Date:   Wed, 08 Feb 2023 12:02:55 +0000
In-Reply-To: <20230208100336.mdnrvpsssa2sjodu@yy-desk-7060>
References: <20230207230436.2690891-1-usama.arif@bytedance.com>
         <20230207230436.2690891-6-usama.arif@bytedance.com>
         <20230208100336.mdnrvpsssa2sjodu@yy-desk-7060>
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On Wed, 2023-02-08 at 18:03 +0800, Yuan Yao wrote:
>=20
> > =C2=A0 #endif
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0/*
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * Sync point with do_wait_c=
pu_initialized(). On boot, all secondary
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * CPUs reach this stage aft=
er receiving INIT/SIPI from do_cpu_up()
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * in the x86/cpu:kick cpuhp=
 stage. At the start of cpu_init() they
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * will wait for do_wait_cpu=
_initialized() to set their bit in
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * smp_callout_mask to relea=
se them.
>=20
> The last sentence of the comment looks confused. The fact is:
>=20
> For serial case, The BSP waits AP to set cpu_initialized_mask from
> wait_for_master_cpu() after fired INIT/SIPI, then AP starts to wait
> cpu_callout_mask set by BSP from do_boot_cpu().
>=20
> Or the comments below "Bringup step two:..." which also looks clear
> enough then above.


	/*
	 * Sync point with do_wait_cpu_initialized(). Before proceeding through
	 * cpu_init(), the AP will call wait_for_master_cpu() which sets its
	 * bit in cpu_initialized_mask and then waits for the BSP to set its
	 * bit in cpu_callout_mask to release it.
	 */
	cpu_init_secondary();


Better?

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