linux-kernel - Re: [PATCH v13 03/16] s390, kexec_file: drop arch_kexec_mem

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Date:   Wed, 29 Aug 2018 09:28:00 +0900
From:   AKASHI Takahiro <takahiro.akashi@...aro.org>
To:     Dave Young <dyoung@...hat.com>
Cc:     Pingfan Liu <piliu@...hat.com>, Philipp Rudo <prudo@...ux.ibm.com>,
        catalin marinas <catalin.marinas@....com>,
        will deacon <will.deacon@....com>, dhowells@...hat.com,
        vgoyal@...hat.com, herbert@...dor.apana.org.au,
        davem@...emloft.net, bhe@...hat.com, arnd@...db.de,
        schwidefsky@...ibm.com, heiko carstens <heiko.carstens@...ibm.com>,
        ard biesheuvel <ard.biesheuvel@...aro.org>,
        james morse <james.morse@....com>, bhsharma@...hat.com,
        kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        "piliu@...hat.com Thiago Jung Bauermann" 
        <bauerman@...ux.vnet.ibm.com>
Subject: Re: [PATCH v13 03/16] s390, kexec_file: drop arch_kexec_mem_walk()

On Tue, Aug 28, 2018 at 09:43:47PM +0800, Dave Young wrote:
> Hi AKASHI,
> On 08/28/18 at 02:21pm, AKASHI Takahiro wrote:
> > Hi Dave,
> > 
> > On Thu, Aug 09, 2018 at 12:14:05AM -0400, Pingfan Liu wrote:
> > > 
> > > 
> > > 
> > > 
> > > ----- Original Message -----
> > > > From: "Dave Young" <dyoung@...hat.com>
> > > > To: "AKASHI Takahiro" <takahiro.akashi@...aro.org>, "Philipp Rudo" <prudo@...ux.ibm.com>, "catalin marinas"
> > > > <catalin.marinas@....com>, "will deacon" <will.deacon@....com>, dhowells@...hat.com, vgoyal@...hat.com,
> > > > herbert@...dor.apana.org.au, davem@...emloft.net, bhe@...hat.com, arnd@...db.de, schwidefsky@...ibm.com, "heiko
> > > > carstens" <heiko.carstens@...ibm.com>, "ard biesheuvel" <ard.biesheuvel@...aro.org>, "james morse"
> > > > <james.morse@....com>, bhsharma@...hat.com, kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
> > > > linux-kernel@...r.kernel.org, "piliu@...hat.com Thiago Jung Bauermann" <bauerman@...ux.vnet.ibm.com>
> > > > Sent: Thursday, August 9, 2018 11:34:16 AM
> > > > Subject: Re: [PATCH v13 03/16] s390, kexec_file: drop arch_kexec_mem_walk()
> > > > 
> > > > Add more cc. Pingfan Liu confirmed ppc does not use 0 as valid address,
> > > > if so it should be safe.
> > > > 
> > > > Pingfan, can you add more words?
> > > > 
> > > 
> > > ppc64 uses a few KB starting from 0 for exception handler.
> > 
> > It assures that 0 (zero) is valid, but won't be assigned as a result of
> > kexec_add_buffer().
> > 
> > So do you think that yet I should submit another patch set, introducing
> > explicit KEXEC_BUF_MEM_UNKNOWN, while assuming 0 by default is safe for now?
> > 
> > Now that this is the only comment against my v13, it's up to you.
> 
> I'm fine with your proposal.  It is simple enough, and we can look into
> it when it becomes a problem in the future which is unlikely.

Ok, thank you for this confirmation.

-Takahiro AKASHI

> Thanks
> Dave