linux-kernel - Re: [PATCH 0/3] iommu/vt-d bad RMRR workarounds

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Date:   Mon, 16 Dec 2019 11:11:37 -0800
From:   "Chen, Yian" <yian.chen@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Barret Rhoden <brho@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        Sohil Mehta <sohil.mehta@...el.com>
Cc:     iommu@...ts.linux-foundation.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] iommu/vt-d bad RMRR workarounds



On 12/13/2019 5:52 PM, Lu Baolu wrote:
>
> On 12/13/19 10:31 PM, Barret Rhoden wrote:
>> On 12/11/19 9:43 PM, Lu Baolu wrote:
>>> The VT-d spec defines the BIOS considerations about RMRR in section 
>>> 8.4:
>>>
>>> "
>>> BIOS must report the RMRR reported memory addresses as reserved (or as
>>> EFI runtime) in the system memory map returned through methods such as
>>> INT15, EFI GetMemoryMap etc.
>>> "
>>>
>>> So we should treat it as firmware bug if the RMRR range is not 
>>> mapped as
>>> RESERVED in the system memory map table.
>>>
>>> As for how should the driver handle this case, ignoring buggy RMRR with
>>> a warning message might be a possible choice.
>>
>> Agreed, firmware should not be doing this.  My first patch just skips 
>> those entries, instead of aborting DMAR processing, and keeps the 
>> warning.
>>
>
> Hi Yian,
>
> Does this work for you?
>
> Best regards,
> baolu
>
>
I made a comment in the the patch email "[PATCH 1/3] iommu/vt-d: skip 
RMRR entries that fail the sanity check "
thanks,
Yian

>> So long as the machine still boots in a safe manner, I'm reasonably 
>> happy.
>>
>> Thanks,
>>
>> Barret
>>
>>