linux-kernel - Re: [PATCH v2] x86/boot: Use EFI setup data if provided

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Date:   Mon, 25 Mar 2019 19:16:44 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Junichi Nomura <j-nomura@...jp.nec.com>
Cc:     Boris Petkov <bp@...en8.de>,
        "fanc.fnst@...fujitsu.com" <fanc.fnst@...fujitsu.com>,
        "bp@...e.de" <bp@...e.de>, "bhe@...hat.com" <bhe@...hat.com>,
        "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 if provided

On 03/25/19 at 10:36am, Junichi Nomura wrote:
> On 3/25/19 7:15 PM, Dave Young wrote:
> > On 03/25/19 at 09:54am, Boris Petkov wrote:
> >> On March 25, 2019 9:27:21 AM GMT+01:00, Junichi Nomura <j-nomura@...jp.nec.com> wrote:
> >>> On 3/25/19 3:59 PM, Dave Young wrote:
> >>>> On 03/25/19 at 06:47am, Junichi Nomura wrote:
> >>>>> On 3/25/19 3:19 PM, Dave Young wrote:
> >>>>>> On 03/25/19 at 02:01pm, Dave Young wrote:
> >>>>>> I think normally people do not see this bug, because kernel will
> >>> set the
> >>>>>> rsdp in boot_params->acpi_rsdp_addr.  Maybe you are testing with
> >>>>>
> >>>>> I think it's only done for file-based kexec interface.
> >>>>
> >>>> Saw Kairui's another reply, yes, kexec-tools need a patch to fill the
> >>>> value as well then.
> >>>>
> >>>> I would vote for a repost of your old patch with some #ifdef
> >>>
> >>> Thanks for comments, Dave, Kairui and Baoquan.
> >>>
> >>> The problem for me is it's a regression in v5.1-rc1, that breaks
> >>> existing setup. If early parsing of RSDP is required only for newly
> >>> supported configuration, I'm fine such configuration requires
> >>> new tools or new options.
> >>>
> >>> This is the 1st version plus #ifdef around the EFI code.
> >>
> >> I'm going to repeat that again until you get it:
> >>
> >> If the kexec kernel should continue to use efi_systab_init() then you
> >> should make efi_get_rsdp_addr() exit early in the kexec-ed kernel.
> > 
> > In that way, early parsing will fail in kexeced kernel, am I missing
> > something?  The early code become complicated but since we have already
> > the early acpi parsing why not to make it consistent in kexeced kernel?
> 
> AFAIU, early parsing is new code in v5.1-rc1 to support kexec on systems
> with hotpluggable memory with KASLR enabled. For systems that requires the
> new feature, it may be ok to say "you need to use another kexec interface"
> and/or "you need new kexec-tools".

Ok, it makes some sense, Kairui mentioned he will work on a kexec-tools
patch then this becomes a must.

Thanks
Dave