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Re: [PATCH 1/4] efi/x86: make efi_memmap_reserve only insert into boot mem areas

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  Re: [PATCH 1/4] efi/x86: make efi_memmap_reserve only insert into  boot mem areas Matt Fleming <matt@codeblueprint.co.uk> - 2017-01-27 16:00 +0100
    Re: [PATCH 1/4] efi/x86: make efi_memmap_reserve only insert into  boot mem areas Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2017-01-27 18:40 +0100
      Re: [PATCH 1/4] efi/x86: make efi_memmap_reserve only insert into  boot mem areas Matt Fleming <matt@codeblueprint.co.uk> - 2017-01-27 23:20 +0100
        Re: [PATCH 1/4] efi/x86: make efi_memmap_reserve only insert into  boot mem areas Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2017-01-27 23:30 +0100

#1568417 — Re: [PATCH 1/4] efi/x86: make efi_memmap_reserve only insert into boot mem areas

On Fri, 13 Jan, at 05:29:52AM, Dave Young wrote:
> 
> It sounds reasonable though I'm still not sure about EFI_LOADER*.
> 
> The main purpose of this patch is to address the invalid mem ranges
> case. As Ard mentioned I will test with Peter's patch first, if it works
> fine I would like to either drop this patch as a future improvement or add
> it at the end of the next post.
> 
> Matt, what's your opinion about the boot_only check and the EFI_LOADERS*
> question?

The main reason that efi_mem_reserve() isn't used for EFI_LOADER
regions today is because we already have a mechanism for reserving it
via memblock_reserve(), which we do during a very early stage of boot
when parsing all the different types of SETUP_* objects.

It's questionable whether it would make sense to switch to
efi_mem_reserve() for EFI_LOADER regions because then you'd
potentially have different APIs for different SETUP_* objects.

As things stand today, I would suggest triggering a WARN_ON() if
someone tries to efi_mem_reserve() an EFI_LOADER region, until/unless
the day comes when a user exists in the kernel.

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#1568542

On 27 January 2017 at 14:48, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> On Fri, 13 Jan, at 05:29:52AM, Dave Young wrote:
>>
>> It sounds reasonable though I'm still not sure about EFI_LOADER*.
>>
>> The main purpose of this patch is to address the invalid mem ranges
>> case. As Ard mentioned I will test with Peter's patch first, if it works
>> fine I would like to either drop this patch as a future improvement or add
>> it at the end of the next post.
>>
>> Matt, what's your opinion about the boot_only check and the EFI_LOADERS*
>> question?
>
> The main reason that efi_mem_reserve() isn't used for EFI_LOADER
> regions today is because we already have a mechanism for reserving it
> via memblock_reserve(), which we do during a very early stage of boot
> when parsing all the different types of SETUP_* objects.
>
> It's questionable whether it would make sense to switch to
> efi_mem_reserve() for EFI_LOADER regions because then you'd
> potentially have different APIs for different SETUP_* objects.
>
> As things stand today, I would suggest triggering a WARN_ON() if
> someone tries to efi_mem_reserve() an EFI_LOADER region, until/unless
> the day comes when a user exists in the kernel.

Hmm, I just queued this. Should we drop it again?

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#1568760

On Fri, 27 Jan, at 05:04:50PM, Ard Biesheuvel wrote:
> On 27 January 2017 at 14:48, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> > On Fri, 13 Jan, at 05:29:52AM, Dave Young wrote:
> >>
> >> It sounds reasonable though I'm still not sure about EFI_LOADER*.
> >>
> >> The main purpose of this patch is to address the invalid mem ranges
> >> case. As Ard mentioned I will test with Peter's patch first, if it works
> >> fine I would like to either drop this patch as a future improvement or add
> >> it at the end of the next post.
> >>
> >> Matt, what's your opinion about the boot_only check and the EFI_LOADERS*
> >> question?
> >
> > The main reason that efi_mem_reserve() isn't used for EFI_LOADER
> > regions today is because we already have a mechanism for reserving it
> > via memblock_reserve(), which we do during a very early stage of boot
> > when parsing all the different types of SETUP_* objects.
> >
> > It's questionable whether it would make sense to switch to
> > efi_mem_reserve() for EFI_LOADER regions because then you'd
> > potentially have different APIs for different SETUP_* objects.
> >
> > As things stand today, I would suggest triggering a WARN_ON() if
> > someone tries to efi_mem_reserve() an EFI_LOADER region, until/unless
> > the day comes when a user exists in the kernel.
> 
> Hmm, I just queued this. Should we drop it again?

Does dropping it break the entire series?

Having had some time to re-read Dave's commit log, it sounds like it
just papers over a bug, which is that efi_memmap_insert() cannot deal
with reserved entries, which all look like they describe the same
region.

So I guess my question is: Shouldn't you fix that instead of requiring
the caller of efi_memmap_insert() to understand what type of entries
it's mapping?

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#1568763

On 27 January 2017 at 22:13, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> On Fri, 27 Jan, at 05:04:50PM, Ard Biesheuvel wrote:
>> On 27 January 2017 at 14:48, Matt Fleming <matt@codeblueprint.co.uk> wrote:
>> > On Fri, 13 Jan, at 05:29:52AM, Dave Young wrote:
>> >>
>> >> It sounds reasonable though I'm still not sure about EFI_LOADER*.
>> >>
>> >> The main purpose of this patch is to address the invalid mem ranges
>> >> case. As Ard mentioned I will test with Peter's patch first, if it works
>> >> fine I would like to either drop this patch as a future improvement or add
>> >> it at the end of the next post.
>> >>
>> >> Matt, what's your opinion about the boot_only check and the EFI_LOADERS*
>> >> question?
>> >
>> > The main reason that efi_mem_reserve() isn't used for EFI_LOADER
>> > regions today is because we already have a mechanism for reserving it
>> > via memblock_reserve(), which we do during a very early stage of boot
>> > when parsing all the different types of SETUP_* objects.
>> >
>> > It's questionable whether it would make sense to switch to
>> > efi_mem_reserve() for EFI_LOADER regions because then you'd
>> > potentially have different APIs for different SETUP_* objects.
>> >
>> > As things stand today, I would suggest triggering a WARN_ON() if
>> > someone tries to efi_mem_reserve() an EFI_LOADER region, until/unless
>> > the day comes when a user exists in the kernel.
>>
>> Hmm, I just queued this. Should we drop it again?
>
> Does dropping it break the entire series?
>
> Having had some time to re-read Dave's commit log, it sounds like it
> just papers over a bug, which is that efi_memmap_insert() cannot deal
> with reserved entries, which all look like they describe the same
> region.
>

No, it cannot deal with bogus entries, and Peter already fixed that.
Dave confirmed that Peter's patch (the one we moved from next to
urgen) made the problem go away.

> So I guess my question is: Shouldn't you fix that instead of requiring
> the caller of efi_memmap_insert() to understand what type of entries
> it's mapping?

Indeed. So I don't think the patch is actually needed anymore

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