linux-kernel - Re: kexec reboot failed due to commit 75d090fd167ac

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Message-ID: <20230908123233.dpbpohgrbyyxekzk@box.shutemov.name>
Date:   Fri, 8 Sep 2023 15:32:33 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Aaron Lu <aaron.lu@...el.com>, Kees Cook <keescook@...omium.org>
Cc:     Bagas Sanjaya <bagasdotme@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>
Subject: Re: kexec reboot failed due to commit 75d090fd167ac

On Fri, Sep 08, 2023 at 02:02:30PM +0800, Aaron Lu wrote:
> On Thu, Sep 07, 2023 at 04:14:09PM +0300, Kirill A. Shutemov wrote:
> > On Tue, Aug 29, 2023 at 10:04:51PM +0800, Aaron Lu wrote:
> > > > Could you show dmesg of the first kernel before kexec?
> > > 
> > > Attached.
> > > 
> > > BTW, kexec is invoked like this:
> > > kver=6.4.0-rc5-00009-g75d090fd167a
> > > kdir=$HOME/kernels/$kver
> > > sudo kexec -l $kdir/vmlinuz-$kver --initrd=$kdir/initramfs-$kver.img --append="root=UUID=4381321e-e01e-455a-9d46-5e8c4c5b2d02 ro net.ifnames=0 acpi_rsdp=0x728e8014 no_hash_pointers sched_verbose selinux=0"
> > 
> > I don't understand why it happens.
> > 
> > Could you check if this patch changes anything:
> > 
> > diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> > index 94b7abcf624b..172c476ff6f3 100644
> > --- a/arch/x86/boot/compressed/misc.c
> > +++ b/arch/x86/boot/compressed/misc.c
> > @@ -456,10 +456,12 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
> >  
> >  	debug_putstr("\nDecompressing Linux... ");
> >  
> > +#if 0
> >  	if (init_unaccepted_memory()) {
> >  		debug_putstr("Accepting memory... ");
> >  		accept_memory(__pa(output), __pa(output) + needed_size);
> >  	}
> > +#endif
> >  
> >  	__decompress(input_data, input_len, NULL, NULL, output, output_len,
> >  			NULL, error);
> > -- 
> 
> It solved the problem.

Looks like increasing BOOT_INIT_PGT_SIZE fixes the issue. I don't yet
understand why and how unaccepted memory is involved. I will look more
into it.

Enabling CONFIG_RANDOMIZE_BASE also makes the issue go away.

Kees, maybe you have a clue?

diff --git a/arch/x86/include/asm/boot.h b/arch/x86/include/asm/boot.h
index 9191280d9ea3..26ccce41d781 100644
--- a/arch/x86/include/asm/boot.h
+++ b/arch/x86/include/asm/boot.h
@@ -40,7 +40,7 @@
 #ifdef CONFIG_X86_64
 # define BOOT_STACK_SIZE	0x4000
 
-# define BOOT_INIT_PGT_SIZE	(6*4096)
+# define BOOT_INIT_PGT_SIZE	(7*4096)
 # ifdef CONFIG_RANDOMIZE_BASE
 /*
  * Assuming all cross the 512GB boundary:
-- 
  Kiryl Shutsemau / Kirill A. Shutemov