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Subject: Re: [PATCH 5.4 v3 1/1] iommu/vt-d: Fix agaw for a supported 48 bit
 guest address width
From:   Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
In-Reply-To: <YHVJDM4CXINrO1KE@kroah.com>
Date:   Tue, 13 Apr 2021 11:05:34 -0700
Cc:     Lu Baolu <baolu.lu@linux.intel.com>,
        "# v4 . 16+" <stable@vger.kernel.org>,
        Camille Lu <camille.lu@hpe.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Joerg Roedel <joro@8bytes.org>,
        iommu@lists.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Transfer-Encoding: quoted-printable
Message-Id: <0C3869E0-63C9-42D5-AAE2-D9D24011B93E@oracle.com>
References: <20210412202736.70765-1-saeed.mirzamohammadi@oracle.com>
 <YHVJDM4CXINrO1KE@kroah.com>
To:     Greg KH <gregkh@linuxfoundation.org>
Precedence: bulk

Hi Greg,

I don=E2=80=99t have any commit ID since the fix is not in mainline or =
any Linus=E2=80=99 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@linuxfoundation.org> =
wrote:
>=20
>=20
> 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.
>>=20
>> 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)."
>>=20
>> This causes domain initialization to fail and following
>> errors appear for EHCI PCI driver:
>>=20
>> [    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
>>=20
>> 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.
>>=20
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com>
>> Tested-by: Camille Lu <camille.lu@hpe.com>
>> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
>=20
> What is the git commit id of this patch in Linus's tree?
>=20
> thanks,
>=20
> greg k-h