Re: [PATCH v13 03/16] s390, kexec_file: drop arch_kexec_mem_walk()

From: AKASHI Takahiro <takahiro.akashi@linaro.org>
To: Dave Young <dyoung@redhat.com>
Cc: Pingfan Liu <piliu@redhat.com>,
	Philipp Rudo <prudo@linux.ibm.com>,
	catalin marinas <catalin.marinas@arm.com>,
	will deacon <will.deacon@arm.com>,
	dhowells@redhat.com, vgoyal@redhat.com,
	herbert@gondor.apana.org.au, davem@davemloft.net, bhe@redhat.com,
	arnd@arndb.de, schwidefsky@de.ibm.com,
	heiko carstens <heiko.carstens@de.ibm.com>,
	ard biesheuvel <ard.biesheuvel@linaro.org>,
	james morse <james.morse@arm.com>,
	bhsharma@redhat.com, kexec@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	"piliu@redhat.com Thiago Jung Bauermann" 
	<bauerman@linux.vnet.ibm.com>
Subject: Re: [PATCH v13 03/16] s390, kexec_file: drop arch_kexec_mem_walk()
Date: Wed, 29 Aug 2018 09:28:00 +0900	[thread overview]
Message-ID: <20180829002759.GG12252@linaro.org> (raw)
In-Reply-To: <20180828134347.GB12178@dhcp-128-65.nay.redhat.com>

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@redhat.com>
> > > > To: "AKASHI Takahiro" <takahiro.akashi@linaro.org>, "Philipp Rudo" <prudo@linux.ibm.com>, "catalin marinas"
> > > > <catalin.marinas@arm.com>, "will deacon" <will.deacon@arm.com>, dhowells@redhat.com, vgoyal@redhat.com,
> > > > herbert@gondor.apana.org.au, davem@davemloft.net, bhe@redhat.com, arnd@arndb.de, schwidefsky@de.ibm.com, "heiko
> > > > carstens" <heiko.carstens@de.ibm.com>, "ard biesheuvel" <ard.biesheuvel@linaro.org>, "james morse"
> > > > <james.morse@arm.com>, bhsharma@redhat.com, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org,
> > > > linux-kernel@vger.kernel.org, "piliu@redhat.com Thiago Jung Bauermann" <bauerman@linux.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