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

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Message-ID: <8a530d5c-22e1-3c2f-98df-45028cc6c771@google.com>
Date:   Fri, 13 Dec 2019 09:31:36 -0500
From:   Barret Rhoden <brho@...gle.com>
To:     Lu Baolu <baolu.lu@...ux.intel.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:     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 12/11/19 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.

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

Thanks,

Barret