linux-kernel - Re: [PATCH v2 0/5] kdump: crashkernel reservation from CMA

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Message-ID: <aDgmu2im03zrBZlt@tiehlicka>
Date: Thu, 29 May 2025 11:19:55 +0200
From: Michal Hocko <mhocko@...e.com>
To: David Hildenbrand <david@...hat.com>
Cc: Baoquan He <bhe@...hat.com>, Donald Dutile <ddutile@...hat.com>,
	Jiri Bohac <jbohac@...e.cz>, Vivek Goyal <vgoyal@...hat.com>,
	Dave Young <dyoung@...hat.com>, kexec@...ts.infradead.org,
	Philipp Rudo <prudo@...hat.com>, Pingfan Liu <piliu@...hat.com>,
	Tao Liu <ltao@...hat.com>, linux-kernel@...r.kernel.org,
	David Hildenbrand <dhildenb@...hat.com>
Subject: Re: [PATCH v2 0/5] kdump: crashkernel reservation from CMA

On Thu 29-05-25 09:46:28, Michal Hocko wrote:
> On Wed 28-05-25 23:01:04, David Hildenbrand wrote:
> [...]
> > I think we just have to be careful to document it properly -- especially the
> > shortcomings and that this feature might become a problem in the future.
> > Movable user-space page tables getting placed on CMA memory would probably
> > not be a problem if we don't care about ... user-space data either way.
> 
> I think makedumpfile could refuse to capture a dump if userspace memory
> is requested to enforce this.
> 
> > The whole "Direct I/O takes max 1s" part is a bit shaky. Maybe it could be
> > configurable how long to wait? 10s is certainly "safer".
> 
> Quite honestly we will never know and rather than making this
> configurable I would go with reasonably large. Couple of seconds
> certainly do not matter for the kdump situations but I would go as far

typo
s@I would go@I would not go@

> as minutes.

-- 
Michal Hocko
SUSE Labs