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a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1748599605; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=oTc0O1aCLWM1UbhnV91t7SUS7ltmWzNQHuNqAgRfetQ=; b=OM/sFBq0rL7Vs7xXiVCe8dcsY021Y2a25yLjl8eZjebZCN8c2CMUPMMzr5ZuEET05jj8z1 iT0fAKgDMQkh8CwYPzhK292SFHDRdpuPxPXp11EP9i2yNWLUPcMIZJM1XNMcWydJa89EnE JYvbP/9jhTV+HDH7uGneBWa9vgT0PIA= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1748599605; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=oTc0O1aCLWM1UbhnV91t7SUS7ltmWzNQHuNqAgRfetQ=; b=rBudCxP3JBcJYezhOTJhuh8HXGvJDmBpmWCUAq4jQ2hF3jfpMLyVNaCy28LC59D3h3LR5A K3kYFOsqxSnNh9Aw== Date: Fri, 30 May 2025 12:06:45 +0200 From: Jiri Bohac To: David Hildenbrand Cc: Michal Hocko , Baoquan He , Donald Dutile , Vivek Goyal , Dave Young , kexec@lists.infradead.org, Philipp Rudo , Pingfan Liu , Tao Liu , linux-kernel@vger.kernel.org, David Hildenbrand Subject: Re: [PATCH v2 0/5] kdump: crashkernel reservation from CMA Message-ID: References: <04a49de5-eb79-431b-ba5b-eae2536781c6@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.997]; MIME_GOOD(-0.10)[text/plain]; MISSING_XM_UA(0.00)[]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_TWELVE(0.00)[12]; ARC_NA(0.00)[]; RCVD_COUNT_ZERO(0.00)[0]; MID_RHS_MATCH_FROMTLD(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.cz:email,dwarf.suse.cz:mid,localhost:helo] X-Spam-Level: X-Spam-Flag: NO X-Spam-Score: -4.30 On Fri, May 30, 2025 at 11:47:46AM +0200, David Hildenbrand wrote: > > > > crashkernel=1G,cma,cma_sane_dma # no wait on transition > > > > > > But is no wait ok? I mean, any O_DIRECT with any device would at least take > > > a bit, no? > > > > > > Of course, there is a short time between the crash and actually triggerying > > > kdump. > > > > > > > crashkernel=1G,cma # wait on transition with e.g. 10s timeout > > > > > > In general, would work for me. > > > > I don't like extending the crashkernel= syntax like this. > > It would make hooking into the generic parsing code in > > parse_crashkernel() really ugly. The syntax is already > > convoluted as is and hard enough to explain in the documentation. > > Would another boolean flag (on top of the other one you are adding) really > make this significantly more ugly? the current code does not split the parameter by commas and treat the part as boolean flags. Both ",cma" and ",cma,cma_sane_dma" (and possibly ",cma_sane_dma,cma") would need to be added to suffix_tbl[] (carefully thinking about the order because one is a prefix of the other); then handled almost the same except setting the flag. Also I think using the command line is way less flexible than sysfs. E.g. the userspace tool loading the crash kernel (kdump) may want to decide if the hardware is sane using its own whitelist/blacklist... > > I am inclined to just setting the fixed delay to 10s for now and > > adding a sysfs knob later if someone asks for it. > > > > Would that work for you? > > Sure. We could always add such a flag later if it's really a problem for > someone. OK, thanks! Will post the v4 shortly. -- Jiri Bohac SUSE Labs, Prague, Czechia