linux-kernel - Re: [tip regression] efi: Allow drivers to reserve boot services forever == toxic

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Date:   Fri, 16 Sep 2016 15:45:20 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Matt Fleming <matt@...eblueprint.co.uk>
Cc:     Mike Galbraith <umgwanakikbuti@...il.com>,
        Ingo Molnar <mingo@...e.hu>,
        LKML <linux-kernel@...r.kernel.org>, linux-efi@...r.kernel.org,
        Peter Jones <pjones@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [tip regression]  efi: Allow drivers to reserve boot services
 forever == toxic

On Fri, Sep 16, 2016 at 03:30:07PM +0100, Matt Fleming wrote:
> On Fri, 16 Sep, at 12:00:59PM, Mike Galbraith wrote:
> > 
> > Ok, here's the whole thing just in case.  Hope it's not too big.
>  
> [...]
> 
> > [    0.000000] esrt: Reserving ESRT space from 0x00000000def87998 to 0x00000000def879d0.
> 
> OK, that's 56 bytes and yet I realise that at no point in the
> efi_mem_reserve() call path do we round up to the nearest page size
> even though the EFI memory map only deals with EFI_PAGE_SIZE regions.

I note that the base is also not aligned to EFI_PAGE_SIZE. Shouldn't we
round that down, too?

[...]

> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
> index f14b7a9da24b..e881b4b2ffd6 100644
> --- a/arch/x86/platform/efi/quirks.c
> +++ b/arch/x86/platform/efi/quirks.c
> @@ -201,8 +201,10 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
>  		return;
>  	}
>  
> +	size = round_up(size, EFI_PAGE_SIZE);

i.e. have:

	size += addr % EFI_PAGE_SIZE;
	size = round_up(size, EFI_PAGE_SIZE);
	addr = round_down(base, EFI_PAGE_SIZE);

Thanks,
Mark.