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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/microcode: Adjust ramdisk address when accessing by virtual address
Date: Mon, 19 Dec 2016 20:27:29 -0500	[thread overview]
Message-ID: <22d4e277-81bb-ef10-3f55-f8f947df60e8@oracle.com> (raw)
In-Reply-To: <20161219233229.p5uw2thbl55o26ds@pd.tnic>



On 12/19/2016 06:32 PM, Borislav Petkov wrote:
> On Mon, Dec 19, 2016 at 07:43:40PM +0100, Borislav Petkov wrote:
>> On Mon, Dec 19, 2016 at 01:12:25PM -0500, Boris Ostrovsky wrote:
>>> IIUIC find_microcode_in_initrd() is called with paging on only on Intel
>>> (which is where I observed it).
>>
>> Ah, that was an important fact. Yes, I can repro it now.
>
> Ok, questions:
>
> * does your guest relocate the ramdisk?


This is not a guest. I crashed with baremetal kernel.


>
> I.e., do you see something like this in dmesg before the splat:
>
> [    0.000000] RAMDISK: [mem 0x7f84c000-0x7ffcffff]
> [    0.000000] Allocated new RAMDISK: [mem 0x3647a000-0x36bfd9e6]
> [    0.000000] Move RAMDISK from [mem 0x7f84c000-0x7ffcf9e6] to [mem 0x3647a000-0x36bfd9e6]
> 	       ^^^^^^^^^^^^^^
>
> If not, then I know what happens.
>
> Also, does it work if you change these lines:
>
>         if (!use_pa && relocated_ramdisk)
>                 start = initrd_start;
>
> to:
>
>         if (!use_pa)
>                 start = initrd_start;

Yes, it does.

I also thought it might be better but I haven't gone through the code to 
make sure this would always work.

I can run more tests tomorrow if you want.

-boris

>
>
> Because if that works, I can actually simplify that function radically.
>
> But more tomorrow.
>
> Thanks.
>

  reply	other threads:[~2016-12-20  1:28 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-19 15:32 Boris Ostrovsky
2016-12-19 15:37 ` Borislav Petkov
2016-12-19 16:10   ` Boris Ostrovsky
2016-12-19 16:40     ` Borislav Petkov
2016-12-19 18:07       ` Borislav Petkov
2016-12-19 18:12         ` Boris Ostrovsky
2016-12-19 18:43           ` Borislav Petkov
2016-12-19 23:32             ` Borislav Petkov
2016-12-20  1:27               ` Boris Ostrovsky [this message]
2016-12-20  1:40                 ` Boris Ostrovsky
2016-12-20 14:40                   ` Borislav Petkov
2016-12-20 19:26                     ` Boris Ostrovsky
2016-12-20 19:31                       ` Borislav Petkov
2016-12-20 22:48                         ` Boris Ostrovsky
2016-12-20 22:55                           ` Borislav Petkov
2016-12-21  9:55                     ` [tip:x86/urgent] x86/microcode/AMD: Reload proper initrd start address tip-bot for Borislav Petkov

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