linux-kernel - Re: [PATCH 5.4 v3 1/1] iommu/vt-d: Fix agaw for a supported 48 bit guest address width

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Message-Id: <0C3869E0-63C9-42D5-AAE2-D9D24011B93E@oracle.com>
Date:   Tue, 13 Apr 2021 11:05:34 -0700
From:   Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Lu Baolu <baolu.lu@...ux.intel.com>,
        "# v4 . 16+" <stable@...r.kernel.org>,
        Camille Lu <camille.lu@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5.4 v3 1/1] iommu/vt-d: Fix agaw for a supported 48 bit
 guest address width

Hi Greg,

I don’t have any commit ID since the fix is not in mainline or any Linus’ tree yet. The driver has completely changed for newer stable versions (and also mainline) and the fix only applies for 5.4, 4.19, and 4.14 stable kernels.

Thanks,
Saeed


> On Apr 13, 2021, at 12:32 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
> 
> 
> On Mon, Apr 12, 2021 at 01:27:35PM -0700, Saeed Mirzamohammadi wrote:
>> The IOMMU driver calculates the guest addressability for a DMA request
>> based on the value of the mgaw reported from the IOMMU. However, this
>> is a fused value and as mentioned in the spec, the guest width
>> should be calculated based on the minimum of supported adjusted guest
>> address width (SAGAW) and MGAW.
>> 
>> This is from specification:
>> "Guest addressability for a given DMA request is limited to the
>> minimum of the value reported through this field and the adjusted
>> guest address width of the corresponding page-table structure.
>> (Adjusted guest address widths supported by hardware are reported
>> through the SAGAW field)."
>> 
>> This causes domain initialization to fail and following
>> errors appear for EHCI PCI driver:
>> 
>> [    2.486393] ehci-pci 0000:01:00.4: EHCI Host Controller
>> [    2.486624] ehci-pci 0000:01:00.4: new USB bus registered, assigned bus
>> number 1
>> [    2.489127] ehci-pci 0000:01:00.4: DMAR: Allocating domain failed
>> [    2.489350] ehci-pci 0000:01:00.4: DMAR: 32bit DMA uses non-identity
>> mapping
>> [    2.489359] ehci-pci 0000:01:00.4: can't setup: -12
>> [    2.489531] ehci-pci 0000:01:00.4: USB bus 1 deregistered
>> [    2.490023] ehci-pci 0000:01:00.4: init 0000:01:00.4 fail, -12
>> [    2.490358] ehci-pci: probe of 0000:01:00.4 failed with error -12
>> 
>> This issue happens when the value of the sagaw corresponds to a
>> 48-bit agaw. This fix updates the calculation of the agaw based on
>> the minimum of IOMMU's sagaw value and MGAW.
>> 
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
>> Tested-by: Camille Lu <camille.lu@....com>
>> Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>
> 
> What is the git commit id of this patch in Linus's tree?
> 
> thanks,
> 
> greg k-h