linux-kernel - Re: [PATCH] x86/kexec: always ensure EFI systab region is mapped

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Date:   Wed, 24 Apr 2019 07:36:55 -0400
From:   Kairui Song <kasong@...hat.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     Dave Young <dyoung@...hat.com>,
        Junichi Nomura <j-nomura@...jp.nec.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>
Subject: Re: [PATCH] x86/kexec: always ensure EFI systab region is mapped

On Wed, Apr 24, 2019, 03:46 Baoquan He <bhe@...hat.com> wrote:
>
> On 04/24/19 at 02:18pm, Dave Young wrote:
> > On 04/24/19 at 01:41pm, Baoquan He wrote:
> > > On 04/24/19 at 02:47am, Junichi Nomura wrote:
> > > > On 4/24/19 2:15 AM, Kairui Song wrote:
> > > > > On Mon, Apr 22, 2019 at 11:21 PM Junichi Nomura <j-nomura@...jp.nec.com> wrote:
> > > > >> Is the mapping of ACPI tables just by luck, too?
> > > > >
> > > > > Good question, they should have same issue with systab, I ignored this one.
> > > > > Then in first kernel when doing kexec it should ensure both ACPI
> > > > > tables and the EFI systab are mapped, that should cover everything and
> > > > > make it work.
> > > >
> > > > Right.
> > > >
> > > > > Is there anything else missing?
> > > > No, as far as I looked around get_rsdp_addr().
> > >
> > > Have made a draft patch to build ident mapping for ACPI tables too, it's
> > > based on Kairui's patch. Dave has tested on his t400s laptop, and
> > > passed. Please check if this adding is OK.
> > >
> > > Kairui, you can add this into your patch to make a new one and resend.
> > > Or I can combine them and send for you today.
>
> >
> > Since I can not reproduce the acpi table accessing fault with Kairui's patch,
> > the test is just sanity testing on same hardware. But the patch looks
> > good.
>
> Yes, usually vendor will put these efi systab, ACPI tables together. See
> the regions you listed on your t420 laptop in another mail:
> da99f000 - dae9efff Reserved (efi systab fall in this region)
> daf9f000 - daffefff ACPI tables
>
> We build 1:1 mapping for kexec kernel down to PMD level. Means for a
> region, it will align starting address down to PMD size, and align end
> address up to PMD size. So the end of efi systab, 0xdae9efff, will cause
> mapping built for the 2MB area, 0xdae00000-0xdaf00000. Clearly ACPI
> tables are covered by that PMD entry. That's why only efi systab
> mapping is built, accessing ACPI tables doesn't cause error.
>
> But we can't assume they will be put together always, so need map ACPI
> tables too.
>
> >
> > With Kairui's fix+ this acpi fix and Junichi's patch everything works.
> > Can anyone send them for example patch 1/2: kexec early mapping for
> > efi/acpi,  patch 2/2: Junichi's previous patch.
>
> Kairui is having a workshop in the US, I can make a patchset to
> include these two patches.
>
> For patch 1/2, I will combine the patch Kairui posted and my draft patch,
> Kairui is the author certainly, since he debugged and found out the root
> cause, and posted v1 when I was on vacation last week.
>
> For patch 2/2, I think the version Boris organized is good.
> http://lkml.kernel.org/r/20190416095209.GG27892@zn.tnic
>

Thanks a lot Bao! I was offline for about 1 day due to timezone and
flight, I have no problem with this and the ACPI mapping part looks
good to me.