linux-kernel - RE: [PATCH] x86/hyperv: Suspend/resume the VP assist page for hibernation

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Message-ID: <HK0P153MB0273F49C7C59012A6BE0B304BFD90@HK0P153MB0273.APCP153.PROD.OUTLOOK.COM>
Date:   Fri, 17 Apr 2020 22:44:39 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Wei Liu <wei.liu@...nel.org>
CC:     "bp@...en8.de" <bp@...en8.de>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "hpa@...or.com" <hpa@...or.com>, KY Srinivasan <kys@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        vkuznets <vkuznets@...hat.com>
Subject: RE: [PATCH] x86/hyperv: Suspend/resume the VP assist page for
 hibernation

> From: Wei Liu <wei.liu@...nel.org>
> Sent: Friday, April 17, 2020 2:08 AM
> > @@ -72,7 +72,8 @@ static int hv_cpu_init(unsigned int cpu)
> >  	struct page *pg;
> >
> >  	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> > -	pg = alloc_page(GFP_KERNEL);
> > +	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
> > +	pg = alloc_page(GFP_ATOMIC);
> 
> IMHO it would be better to  only tap into the reserve pool if so
> required, e.g.
> 
>         pg = alloc_page(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL);
> 
> Wei.

Ok, I'll follow the suggestion.

BTW, there are indeed some usages like this, but not a lot:
grep irqs_disabled drivers/acpi include/acpi drivers/trace -nr |grep GFP_ATOMIC | grep GFP_KERNEL

Thanks,
-- Dexuan