linux-kernel - RE: [PATCH][v10] PM / hibernate: Verify the consistent of e820 memory map by md5 digest

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Date:   Sun, 25 Sep 2016 03:44:03 +0000
From:   "Chen, Yu C" <yu.c.chen@...el.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
CC:     Linux PM <linux-pm@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        Pavel Machek <pavel@....cz>, Lee Chun-Yi <jlee@...e.com>,
        Borislav Petkov <bp@...en8.de>
Subject: RE: [PATCH][v10] PM / hibernate: Verify the consistent of e820
 memory map by md5 digest

Hi,
Sorry for late response, I missed the thread in mailbox,

> -----Original Message-----
> From: rjwysocki@...il.com [mailto:rjwysocki@...il.com] On Behalf Of
> Rafael J. Wysocki
> Sent: Monday, September 19, 2016 7:46 PM
> To: Chen, Yu C
> Cc: Linux PM; the arch/x86 maintainers; Linux Kernel Mailing List; Thomas
> Gleixner; Ingo Molnar; H. Peter Anvin; Wysocki, Rafael J; Pavel Machek; Lee
> Chun-Yi; Borislav Petkov
> Subject: Re: [PATCH][v10] PM / hibernate: Verify the consistent of e820
> memory map by md5 digest
> 
> On Fri, Sep 9, 2016 at 2:21 PM, Chen Yu <yu.c.chen@...el.com> wrote:
> > On some platforms, there is occasional panic triggered when trying to
> > resume from hibernation, a typical panic looks like:
> 
> [cut]
> 
> > @@ -211,10 +292,15 @@ int arch_hibernation_header_save(void *addr,
> unsigned int max_size)
> >   */
> >  int arch_hibernation_header_restore(void *addr)  {
> > +       bool e820_mismatch = false;
> 
> The extra local variable can be avoided if you structure the code slightly
> differently.
> 
> >         struct restore_data_record *rdr = addr;
> >
> >         restore_jump_address = rdr->jump_address;
> >         jump_address_phys = rdr->jump_address_phys;
> >         restore_cr3 = rdr->cr3;
> > -       return (rdr->magic == RESTORE_MAGIC) ? 0 : -EINVAL;
> > +
> > +       e820_mismatch = hibernation_e820_mismatch(rdr->e820_digest);
> 
> Also calling hibernation_e820_mismatch() before checking rdr->magic may not
> be useful at all.
> 
Yes.
> > +
> > +       return (rdr->magic == RESTORE_MAGIC) ?
> > +               (e820_mismatch ? -ENODEV : 0) : -EINVAL;
> 
> So what about:
> 
> if (rdr->magic != RESTORE_MAGIC)
>         return -EINVAL;
> 
> if (hibernation_e820_mismatch(rdr->e820_digest))
>         return -ENODEV;
> 
> return 0;
> 
> 
Ok, will change it to this one. Thanks.
> >  }
> > --
> 
> Thanks,
> Rafael


Thanks,
Yu