linux-kernel - Re: [PATCH V11 08/11] drivers: acpi: Handle IOMMU lookup failure with deferred probing or error

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Message-ID: <647cbf74-d171-365c-7ef5-9f1e5986716c@codeaurora.org>
Date:   Tue, 23 May 2017 07:27:38 -0400
From:   Nate Watterson <nwatters@...eaurora.org>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sricharan R <sricharan@...eaurora.org>
Cc:     robin.murphy@....com, will.deacon@....com, joro@...tes.org,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, m.szyprowski@...sung.com,
        bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-acpi@...r.kernel.org, tn@...ihalf.com, hanjun.guo@...aro.org,
        okaya@...eaurora.org, robh+dt@...nel.org, frowand.list@...il.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        sudeep.holla@....com, rjw@...ysocki.net, lenb@...nel.org,
        catalin.marinas@....com, arnd@...db.de, linux-arch@...r.kernel.org,
        gregkh@...uxfoundation.org
Subject: Re: [PATCH V11 08/11] drivers: acpi: Handle IOMMU lookup failure with
 deferred probing or error

Hi Lorenzo,

On 5/23/2017 5:26 AM, Lorenzo Pieralisi wrote:
> On Tue, May 23, 2017 at 02:31:17PM +0530, Sricharan R wrote:
>> Hi Lorenzo,
>>
>> On 5/23/2017 2:22 PM, Lorenzo Pieralisi wrote:
>>> On Tue, May 23, 2017 at 02:26:10AM -0400, Nate Watterson wrote:
>>>> Hi Sricharan,
>>>>
>>>> On 4/10/2017 7:21 AM, Sricharan R wrote:
>>>>> This is an equivalent to the DT's handling of the iommu master's probe
>>>>> with deferred probing when the corrsponding iommu is not probed yet.
>>>>> The lack of a registered IOMMU can be caused by the lack of a driver for
>>>>> the IOMMU, the IOMMU device probe not having been performed yet, having
>>>>> been deferred, or having failed.
>>>>>
>>>>> The first case occurs when the firmware describes the bus master and
>>>>> IOMMU topology correctly but no device driver exists for the IOMMU yet
>>>>> or the device driver has not been compiled in. Return NULL, the caller
>>>>> will configure the device without an IOMMU.
>>>>>
>>>>> The second and third cases are handled by deferring the probe of the bus
>>>>> master device which will eventually get reprobed after the IOMMU.
>>>>>
>>>>> The last case is currently handled by deferring the probe of the bus
>>>>> master device as well. A mechanism to either configure the bus master
>>>>> device without an IOMMU or to fail the bus master device probe depending
>>>>> on whether the IOMMU is optional or mandatory would be a good
>>>>> enhancement.
>>>>>
>>>>> Tested-by: Hanjun Guo <hanjun.guo@...aro.org>
>>>>> Reviewed-by: Robin Murphy <robin.murphy@....com>
>>>>> [Lorenzo: Added fixes for dma_coherent_mask overflow, acpi_dma_configure
>>>>>            called multiple times for same device]
>>>>> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
>>>>> Signed-off-by: Sricharan R <sricharan@...eaurora.org>
>>>>> ---
>>>>>   drivers/acpi/arm64/iort.c  | 33 ++++++++++++++++++++++++++++++++-
>>>>>   drivers/acpi/scan.c        | 11 ++++++++---
>>>>>   drivers/base/dma-mapping.c |  2 +-
>>>>>   include/acpi/acpi_bus.h    |  2 +-
>>>>>   include/linux/acpi.h       |  7 +++++--
>>>>>   5 files changed, 47 insertions(+), 8 deletions(-)
>>>>>
>>>>> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
>>>>> index 3dd9ec3..e323ece 100644
>>>>> --- a/drivers/acpi/arm64/iort.c
>>>>> +++ b/drivers/acpi/arm64/iort.c
>>>>> @@ -543,6 +543,14 @@ static const struct iommu_ops *iort_iommu_xlate(struct device *dev,
>>>>>   	const struct iommu_ops *ops = NULL;
>>>>>   	int ret = -ENODEV;
>>>>>   	struct fwnode_handle *iort_fwnode;
>>>>> +	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
>>>>> +
>>>>> +	/*
>>>>> +	 * If we already translated the fwspec there
>>>>> +	 * is nothing left to do, return the iommu_ops.
>>>>> +	 */
>>>>> +	if (fwspec && fwspec->ops)
>>>>> +		return fwspec->ops;
>>>>
>>>> Is this logic strictly required? It breaks masters with multiple SIDs
>>>> as only the first SID is actually added to the master's fwspec.
>>>
>>> My bad, that's indeed a silly bug I introduced. Please let me know if the
>>> patch below fixes it, we will send it upstream shortly.
>>>
>>
>> oops, i think emails crossed. Please let me know if you are ok to add
>> this to the other fixes.
> 
> No worries, yes I am ok thanks but please give Nate some time to report
> back to make sure the diff I sent actually fixes the problem.

The patch you sent fixes the problem. Thanks for the quick turnaround.

> 
> Apologies for the breakage.
> 
> Lorenzo
> 
>>
>> Regards,
>>   Sricharan
>>

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