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From: AKASHI Takahiro <takahiro.akashi@linaro.org>
To: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: kexec@lists.infradead.org, dyoung@redhat.com, vgoyal@redhat.com,
	bhe@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kexec: allocate buffer in top-down, if specified, correctly
Date: Fri, 28 Apr 2017 09:51:39 +0900	[thread overview]
Message-ID: <20170428005135.GA3963@fireball> (raw)
In-Reply-To: <1605356.Vp6YPvtjly@morokweng>

Thiago,

Thank you for the comment.

On Thu, Apr 27, 2017 at 07:00:04PM -0300, Thiago Jung Bauermann wrote:
> Hello,
> 
> Am Mittwoch, 26. April 2017, 17:22:09 BRT schrieb AKASHI Takahiro:
> > The current kexec_locate_mem_hole(kbuf.top_down == 1) stops searching at
> > the first memory region that has enough space for requested size even if
> > some of higher regions may also have.
> 
> kexec_locate_mem_hole expects arch_kexec_walk_mem to walk memory from top to 
> bottom if top_down is true. That is what powerpc's version does.

Ah, I haven't noticed that, but x86 doesn't have arch_kexec_walk_mem and
how can it work for x86?

> Isn't it possible to walk resources from top to bottom?

Yes, it will be, but it seems to me that such a behavior is not intuitive
and even confusing if it doesn't come with explicit explanation.

> > This behavior is not consistent with locate_hole(hole_end == -1) function
> > of kexec-tools.
> > 
> > This patch fixes the bug, going though all the memory regions anyway.
> 
> This patch would break powerpc, because at the end of the memory walk kbuf 
> would have the lowest memory hole.
> 
> If it's not possible to walk resources in reverse order, then this patch needs 
> to change powerpc to always walk memory from bottom to top.

So I would like to hear from x86 guys.

Thanks
-Takahiro AKASHI

> -- 
> Thiago Jung Bauermann
> IBM Linux Technology Center
> 

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

WARNING: multiple messages have this Message-ID (diff)
From: AKASHI Takahiro <takahiro.akashi@linaro.org>
To: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: dyoung@redhat.com, bhe@redhat.com, vgoyal@redhat.com,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kexec: allocate buffer in top-down, if specified, correctly
Date: Fri, 28 Apr 2017 09:51:39 +0900	[thread overview]
Message-ID: <20170428005135.GA3963@fireball> (raw)
In-Reply-To: <1605356.Vp6YPvtjly@morokweng>

Thiago,

Thank you for the comment.

On Thu, Apr 27, 2017 at 07:00:04PM -0300, Thiago Jung Bauermann wrote:
> Hello,
> 
> Am Mittwoch, 26. April 2017, 17:22:09 BRT schrieb AKASHI Takahiro:
> > The current kexec_locate_mem_hole(kbuf.top_down == 1) stops searching at
> > the first memory region that has enough space for requested size even if
> > some of higher regions may also have.
> 
> kexec_locate_mem_hole expects arch_kexec_walk_mem to walk memory from top to 
> bottom if top_down is true. That is what powerpc's version does.

Ah, I haven't noticed that, but x86 doesn't have arch_kexec_walk_mem and
how can it work for x86?

> Isn't it possible to walk resources from top to bottom?

Yes, it will be, but it seems to me that such a behavior is not intuitive
and even confusing if it doesn't come with explicit explanation.

> > This behavior is not consistent with locate_hole(hole_end == -1) function
> > of kexec-tools.
> > 
> > This patch fixes the bug, going though all the memory regions anyway.
> 
> This patch would break powerpc, because at the end of the memory walk kbuf 
> would have the lowest memory hole.
> 
> If it's not possible to walk resources in reverse order, then this patch needs 
> to change powerpc to always walk memory from bottom to top.

So I would like to hear from x86 guys.

Thanks
-Takahiro AKASHI

> -- 
> Thiago Jung Bauermann
> IBM Linux Technology Center
> 

  reply	other threads:[~2017-04-28  0:52 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-26  8:22 [PATCH] kexec: allocate buffer in top-down, if specified, correctly AKASHI Takahiro
2017-04-26  8:22 ` AKASHI Takahiro
2017-04-27 22:00 ` Thiago Jung Bauermann
2017-04-27 22:00   ` Thiago Jung Bauermann
2017-04-28  0:51   ` AKASHI Takahiro [this message]
2017-04-28  0:51     ` AKASHI Takahiro
2017-04-28  5:19     ` Dave Young
2017-04-28  5:19       ` Dave Young
2017-04-28  5:23       ` Dave Young
2017-04-28  5:23         ` Dave Young
2017-04-28 19:33     ` Thiago Jung Bauermann
2017-04-28 19:33       ` Thiago Jung Bauermann
2017-04-28  4:46 ` Dave Young
2017-04-28  4:46   ` Dave Young

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