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

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Message-ID: <20160916143007.GF16797@codeblueprint.co.uk>
Date:   Fri, 16 Sep 2016 15:30:07 +0100
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Mike Galbraith <umgwanakikbuti@...il.com>
Cc:     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, 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.

Could you try this patch?

-------->8--------

>From a24b38999965808355c461f8490670266162eabf Mon Sep 17 00:00:00 2001
From: Matt Fleming <matt@...eblueprint.co.uk>
Date: Fri, 16 Sep 2016 15:12:47 +0100
Subject: [PATCH] x86/efi: Round EFI memmap reservations to EFI_PAGE_SIZE

Mike reported that his machine started rebooting during boot after,

  commit 8e80632fb23f ("efi/esrt: Use efi_mem_reserve() and avoid a kmalloc()")

The ESRT table on his machine is 56 bytes and at no point in the
efi_arch_mem_reserve() call path is that size rounded up to
EFI_PAGE_SIZE.

Since the EFI memory map only deals with whole pages, inserting an EFI
memory region with 56 bytes results in a new entry covering zero
pages, and completely screws up the calculations for the old regions
that were trimmed.

Round all sizes upwards to the nearest EFI_PAGE_SIZE boundary.

Additionally, efi_memmap_insert() expects the mem::range::end value to
be one less than the end address for the region.

Reported-by: Mike Galbraith <umgwanakikbuti@...il.com>
Cc: Peter Jones <pjones@...hat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
---
 arch/x86/platform/efi/quirks.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

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);
+
 	mr.range.start = addr;
-	mr.range.end = addr + size;
+	mr.range.end = addr + size - 1;
 	mr.attribute = md.attribute | EFI_MEMORY_RUNTIME;

 	num_entries = efi_memmap_split_count(&md, &mr.range);
-- 
2.9.3