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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 20:40:00 -0500	[thread overview]
Message-ID: <b1ad2190-a768-d28f-10be-c1d6da9f384d@oracle.com> (raw)
In-Reply-To: <22d4e277-81bb-ef10-3f55-f8f947df60e8@oracle.com>



On 12/19/2016 08:27 PM, Boris Ostrovsky wrote:
>
>
> 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]
>>            ^^^^^^^^^^^^^^


Sorry, forgot about this: I see the first line but not the other two (so 
the relocation did not occur).


-boris

>>
>> 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  1:40 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
2016-12-20  1:40                 ` Boris Ostrovsky [this message]
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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