linux-kernel - Re: [PATCH v2 1/2] kexec: Add KEXEC_FILE_NO

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Message-ID: <aKbZ1h5mjtfoFMh8@MiWiFi-R3L-srv>
Date: Thu, 21 Aug 2025 16:33:26 +0800
From: Baoquan He <bhe@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>, Brian Mak <makb@...iper.net>
Cc: Dave Young <dyoung@...hat.com>, Alexander Graf <graf@...zon.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>, x86@...nel.org,
	kexec@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] kexec: Add KEXEC_FILE_NO_CMA as a legal flag

On 08/20/25 at 09:47pm, Andrew Morton wrote:
> On Tue, 5 Aug 2025 14:15:26 -0700 Brian Mak <makb@...iper.net> wrote:
> 
> > Commit 07d24902977e ("kexec: enable CMA based contiguous allocation")
> > introduces logic to use CMA-based allocation in kexec by default. As
> > part of the changes, it introduces a kexec_file_load flag to disable the
> > use of CMA allocations from userspace. However, this flag is broken
> > since it is missing from the list of legal flags for kexec_file_load.
> > kexec_file_load returns EINVAL when attempting to use the flag.
> > 
> > Fix this by adding the KEXEC_FILE_NO_CMA flag to the list of legal flags
> > for kexec_file_load.
> > 
> > Fixes: 07d24902977e ("kexec: enable CMA based contiguous allocation")
> 
> A description of the userspace-visible runtime effects of this bug
> would be very helpful, please.  A lot more than "is broken"!
> 
> Also, could we please have some reviewer input on this change?

I didn't receive this patchset, and kexec mailing list is not in CC.
I don't know what happened.

> 
> 
> > --- a/include/linux/kexec.h
> > +++ b/include/linux/kexec.h
> > @@ -460,7 +460,8 @@ bool kexec_load_permitted(int kexec_image_type);
> >  
> >  /* List of defined/legal kexec file flags */
> >  #define KEXEC_FILE_FLAGS	(KEXEC_FILE_UNLOAD | KEXEC_FILE_ON_CRASH | \
> > -				 KEXEC_FILE_NO_INITRAMFS | KEXEC_FILE_DEBUG)
> > +				 KEXEC_FILE_NO_INITRAMFS | KEXEC_FILE_DEBUG | \
> > +				 KEXEC_FILE_NO_CMA)
> >  
> >  /* flag to track if kexec reboot is in progress */
> >  extern bool kexec_in_progress;
> > -- 
> > 2.25.1
> > 
>