linux-kernel - Re: [PATCH v2 06/17] x86/hyperv: allocate output arg pages if required

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Message-ID: <20201113150544.drm4qk4jlchewukg@liuwe-devbox-debian-v2>
Date:   Fri, 13 Nov 2020 15:05:44 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Wei Liu <wei.liu@...nel.org>,
        Linux on Hyper-V List <linux-hyperv@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        Linux Kernel List <linux-kernel@...r.kernel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        Vineeth Pillai <viremana@...ux.microsoft.com>,
        Sunil Muthuswamy <sunilmut@...rosoft.com>,
        Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
        Lillian Grassin-Drake <ligrassi@...rosoft.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 06/17] x86/hyperv: allocate output arg pages if
 required

On Thu, Nov 12, 2020 at 04:35:48PM +0100, Vitaly Kuznetsov wrote:
> Wei Liu <wei.liu@...nel.org> writes:
[...]
> > @@ -209,14 +219,23 @@ static int hv_cpu_die(unsigned int cpu)
> >  	unsigned int new_cpu;
> >  	unsigned long flags;
> >  	void **input_arg;
> > -	void *input_pg = NULL;
> > +	void *pg;
> >  
> >  	local_irq_save(flags);
> >  	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> > -	input_pg = *input_arg;
> > +	pg = *input_arg;
> >  	*input_arg = NULL;
> > +
> > +	if (hv_root_partition) {
> > +		void **output_arg;
> > +
> > +		output_arg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
> > +		*output_arg = NULL;
> > +	}
> > +
> >  	local_irq_restore(flags);
> > -	free_page((unsigned long)input_pg);
> > +
> > +	free_page((unsigned long)pg);
> >  
> 
> Hm, but in case we've allocated output_arg, don't we need to do
> 	free_pages((unsigned long)pg, 1);
> 
> instead?

Indeed. This has been fixed with:

    free_pages((unsigned long)pg, hv_root_partition ? 1 : 0);

Wei.