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

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Message-ID: <02d69d9a-9c45-d9e7-4c1a-cb5e50590c47@linux.intel.com>
Date:   Sat, 14 Dec 2019 09:52:50 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     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>,
        Yian Chen <yian.chen@...el.com>,
        Sohil Mehta <sohil.mehta@...el.com>
Cc:     baolu.lu@...ux.intel.com, 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 12/13/19 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


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