linux-kernel - Re: [PATCH v2] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel

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Message-ID: <20190403082313.GA14838@dhcp-128-65.nay.redhat.com>
Date:   Wed, 3 Apr 2019 16:23:13 +0800
From:   Dave Young <dyoung@...hat.com>
To:     "bhe@...hat.com" <bhe@...hat.com>
Cc:     Chao Fan <fanc.fnst@...fujitsu.com>,
        Junichi Nomura <j-nomura@...jp.nec.com>,
        Borislav Petkov <bp@...en8.de>,
        "kasong@...hat.com" <kasong@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] x86/boot: Use efi_setup_data for searching RSDP on
 kexec-ed kernel

On 04/03/19 at 03:50pm, Baoquan He wrote:
> On 04/03/19 at 03:30pm, Chao Fan wrote:
> > On Wed, Apr 03, 2019 at 02:39:11PM +0800, Dave Young wrote:
> > >> Actually I got some different kexec test results.
> > >> 
> > >> Yesterday, with my installed kernel (based on git head several weeks
> > >> ago), kexec kernel panics.
> > >> 
> > >> Then I tried latest mainline with git pull, everything works, (with or
> > >> without the patch, and can not reproduce the bug this patch is fixing)
> > >> 
> > >> Today, test again, kexec reboot hangs (with or without your patch), but
> > >> kdump works always (with or without the patch)
> > >> 
> > >> It is weird to me. Probably I need find out why I can not reproduce the
> > >> bug this patch is addressing first.
> > >> 
> > >> earlyprintk seems not working for me anymore, it is not easy to debug on
> > >> laptop now.
> > >> 
> > >> But the patch itself is clear, I think it should be good.  There might be
> > >> other things broken.
> > >
> > >Disable your immovable mem code then everything works for me.  There
> > >might be something wrong in the code.  Also "nokaslr" does not help, it
> > >should be another problem 
> > 
> > If "nokaslr" doesn't help, so I think
> > >+      /*num_immovable_mem = count_immovable_mem_regions();*/
> > also doesn't help. I think the problem is from get_rsdp_addr().
> 
> Yes, seems get_rsdp_addr() has issue in this case. I am wondering if we
> can adjust the postion of get_rsdp_addr() calling. If nokaslr is
> specified, no need to get rsdp?

I assumed the early code is only be useful for kaslr, if this is true
then no need to get rsdp in case nokaslr.

But I vaguely remember Boris want the boot_params rsdp pointer be a
general thing, I did not followed up these patch discussions, need to see how Boris thinks about this.

Thanks
Dave