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From: Dan Williams <dan.j.williams@intel.com>
Date: Tue, 3 Jan 2017 18:48:43 -0800
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Subject: Re: [PATCH 08/29] efi: Allow drivers to reserve boot services forever
To: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ingo Molnar <mingo@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-efi@vger.kernel.org, Borislav Petkov <bp@alien8.de>,
        Dave Young <dyoung@redhat.com>,
        Leif Lindholm <leif.lindholm@linaro.org>,
        Mark Rutland <mark.rutland@arm.com>, Peter Jones <pjones@redhat.com>,
        "Verma, Vishal L" <vishal.l.verma@intel.com>, poros@redhat.com
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On Fri, Sep 9, 2016 at 8:18 AM, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> Today, it is not possible for drivers to reserve EFI boot services for
> access after efi_free_boot_services() has been called on x86. For
> ARM/arm64 it can be done simply by calling memblock_reserve().
>
> Having this ability for all three architectures is desirable for a
> couple of reasons,
>
>   1) It saves drivers copying data out of those regions
>   2) kexec reboot can now make use of things like ESRT
>
> Instead of using the standard memblock_reserve() which is insufficient
> to reserve the region on x86 (see efi_reserve_boot_services()), a new
> API is introduced in this patch; efi_mem_reserve().
>
> efi.memmap now always represents which EFI memory regions are
> available. On x86 the EFI boot services regions that have not been
> reserved via efi_mem_reserve() will be removed from efi.memmap during
> efi_free_boot_services().
>
> This has implications for kexec, since it is not possible for a newly
> kexec'd kernel to access the same boot services regions that the
> initial boot kernel had access to unless they are reserved by every
> kexec kernel in the chain.
>
> Tested-by: Dave Young <dyoung@redhat.com> [kexec/kdump]
> Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> [arm]
> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Leif Lindholm <leif.lindholm@linaro.org>
> Cc: Peter Jones <pjones@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>

This commit appears to cause a boot regression between v4.8 and v4.9.

BUG: unable to handle kernel paging request at ffff8830281bf1c8
IP: [<ffffffff81a21266>] __next_mem_range_rev+0x13a/0x1d6
PGD 3193067 PUD 3196067 PTE 80000030281bf060
Oops: 0000 1 SMP DEBUG_PAGEALLOC
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.0+ #2
task: ffffffff82011540 task.stack: ffffffff82000000
RIP: 0010:[<ffffffff81a21266>] [<ffffffff81a21266>]
__next_mem_range_rev+0x13a/0x1d6
RSP: 0000:ffffffff82003dd8 EFLAGS: 00010202
RAX: ffff8830281bf1e0 RBX: ffffffff82003e60 RCX: ffffffff82167490
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000001840000000
RBP: ffffffff82003e18 R08: ffffffff821674b0 R09: 000000000000008f
R10: 000000000000008f R11: ffffffff82011cf0 R12: 0000000000000004
R13: 0000003040000000 R14: 0000000000000000 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff8817e0800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8830281bf1c8 CR3: 000000000200a000 CR4: 00000000007406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 00000000
Stack:
ffffea0000001700 ffffffff82003e50 0000000000000000
00000000000010000000003040000000 ffffffff82003e58 0000000000000180
ffffffffffffffc0
ffffffff82003e98 ffffffff81a21395 ffffffff82003e58 0000000000000000
Call Trace:
[<ffffffff81a21395>] memblock_find_in_range_node+0x93/0x13a
[<ffffffff8221e3b1>] memblock_alloc_range_nid+0x1b/0x3e
[<ffffffff8221e5b9>] __memblock_alloc_base+0x15/0x17
[<ffffffff8221e5cd>] memblock_alloc_base+0x12/0x2e
[<ffffffff8221e5f4>] memblock_alloc+0xb/0xd
[<ffffffff82208e22>] efi_free_boot_services+0x46/0x180
[<ffffffff821e818b>] start_kernel+0x4a1/0x4cc
[<ffffffff821e7ad8>] ? set_init_arg+0x55/0x55
[<ffffffff821e7120>] ? early_idt_handler_array+0x120/0x120
[<ffffffff821e75d6>] x86_64_start_reservations+0x2a/0x2c
[<ffffffff821e7724>] x86_64_start_kernel+0x14c/0x16f
Code: 18 44 89 38 41 8d 44 24 ff 49 c1 e1 20 4c 09 c8 48 89 03 e9 a0
00 00 00 4d 63 d1 4c 89 d0 48 c1 e0 05 49 03 40 18 45 85 c9 74 28 <48>
8b 50 e8 48 03 50 e0 49 83 cb ff 4d 3b 10 73 03 4c 8b 18 49 ^M
RIP [<ffffffff81a21266>] __next_mem_range_rev+0x13a/0x1d6

I also see that Petr may have run into it as well [1]? Petr is this
the same signature you are seeing? Can you post a boot log with
"efi=debug" on the kernel command line?

It also fails on 4.10-rc2.  However, if I revert the following commits
it boots fine:

4bc9f92e64c8 x86/efi-bgrt: Use efi_mem_reserve() to avoid copying image data
8e80632fb23f efi/esrt: Use efi_mem_reserve() and avoid a kmalloc()
816e76129ed5 efi: Allow drivers to reserve boot services forever

[1]: https://lkml.org/lkml/2016/12/21/197