[3/3] iommu/virtio: Enable x86 support
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Message ID 20200214160413.1475396-4-jean-philippe@linaro.org
State New
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  • Untitled series #158630
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Commit Message

Jean-Philippe Brucker Feb. 14, 2020, 4:04 p.m. UTC
With the built-in topology description in place, x86 platforms can now
use the virtio-iommu.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
 drivers/iommu/Kconfig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Michael S. Tsirkin Feb. 16, 2020, 9:50 a.m. UTC | #1
On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote:
> On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote:
> > With the built-in topology description in place, x86 platforms can now
> > use the virtio-iommu.
> > 
> > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > ---
> >   drivers/iommu/Kconfig | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > index 068d4e0e3541..adcbda44d473 100644
> > --- a/drivers/iommu/Kconfig
> > +++ b/drivers/iommu/Kconfig
> > @@ -508,8 +508,9 @@ config HYPERV_IOMMU
> >   config VIRTIO_IOMMU
> >   	bool "Virtio IOMMU driver"
> >   	depends on VIRTIO=y
> > -	depends on ARM64
> > +	depends on (ARM64 || X86)
> >   	select IOMMU_API
> > +	select IOMMU_DMA
> 
> Can that have an "if X86" for clarity? AIUI it's not necessary for
> virtio-iommu itself (and really shouldn't be), but is merely to satisfy the
> x86 arch code's expectation that IOMMU drivers bring their own DMA ops,
> right?
> 
> Robin.

In fact does not this work on any platform now?

> >   	select INTERVAL_TREE
> >   	help
> >   	  Para-virtualised IOMMU driver with virtio.
> >
Jean-Philippe Brucker Feb. 17, 2020, 9:01 a.m. UTC | #2
On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote:
> On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote:
> > On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote:
> > > With the built-in topology description in place, x86 platforms can now
> > > use the virtio-iommu.
> > > 
> > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > > ---
> > >   drivers/iommu/Kconfig | 3 ++-
> > >   1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > > index 068d4e0e3541..adcbda44d473 100644
> > > --- a/drivers/iommu/Kconfig
> > > +++ b/drivers/iommu/Kconfig
> > > @@ -508,8 +508,9 @@ config HYPERV_IOMMU
> > >   config VIRTIO_IOMMU
> > >   	bool "Virtio IOMMU driver"
> > >   	depends on VIRTIO=y
> > > -	depends on ARM64
> > > +	depends on (ARM64 || X86)
> > >   	select IOMMU_API
> > > +	select IOMMU_DMA
> > 
> > Can that have an "if X86" for clarity? AIUI it's not necessary for
> > virtio-iommu itself (and really shouldn't be), but is merely to satisfy the
> > x86 arch code's expectation that IOMMU drivers bring their own DMA ops,
> > right?
> > 
> > Robin.
> 
> In fact does not this work on any platform now?

There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU
has been converted recently [1] but VT-d still implements its own DMA ops
(conversion patches are on the list [2]). On Arm the arch Kconfig selects
IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is
complete. Until then I can add a "if X86" here for clarity.

Thanks,
Jean

[1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/
[2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/
Michael S. Tsirkin Feb. 17, 2020, 1:01 p.m. UTC | #3
On Mon, Feb 17, 2020 at 10:01:07AM +0100, Jean-Philippe Brucker wrote:
> On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote:
> > On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote:
> > > On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote:
> > > > With the built-in topology description in place, x86 platforms can now
> > > > use the virtio-iommu.
> > > > 
> > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > > > ---
> > > >   drivers/iommu/Kconfig | 3 ++-
> > > >   1 file changed, 2 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > > > index 068d4e0e3541..adcbda44d473 100644
> > > > --- a/drivers/iommu/Kconfig
> > > > +++ b/drivers/iommu/Kconfig
> > > > @@ -508,8 +508,9 @@ config HYPERV_IOMMU
> > > >   config VIRTIO_IOMMU
> > > >   	bool "Virtio IOMMU driver"
> > > >   	depends on VIRTIO=y
> > > > -	depends on ARM64
> > > > +	depends on (ARM64 || X86)
> > > >   	select IOMMU_API
> > > > +	select IOMMU_DMA
> > > 
> > > Can that have an "if X86" for clarity? AIUI it's not necessary for
> > > virtio-iommu itself (and really shouldn't be), but is merely to satisfy the
> > > x86 arch code's expectation that IOMMU drivers bring their own DMA ops,
> > > right?
> > > 
> > > Robin.
> > 
> > In fact does not this work on any platform now?
> 
> There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU
> has been converted recently [1] but VT-d still implements its own DMA ops
> (conversion patches are on the list [2]). On Arm the arch Kconfig selects
> IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is
> complete. Until then I can add a "if X86" here for clarity.
> 
> Thanks,
> Jean
> 
> [1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/
> [2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/

What about others? E.g. PPC?
Robin Murphy Feb. 17, 2020, 1:22 p.m. UTC | #4
On 17/02/2020 1:01 pm, Michael S. Tsirkin wrote:
> On Mon, Feb 17, 2020 at 10:01:07AM +0100, Jean-Philippe Brucker wrote:
>> On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote:
>>> On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote:
>>>> On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote:
>>>>> With the built-in topology description in place, x86 platforms can now
>>>>> use the virtio-iommu.
>>>>>
>>>>> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
>>>>> ---
>>>>>    drivers/iommu/Kconfig | 3 ++-
>>>>>    1 file changed, 2 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
>>>>> index 068d4e0e3541..adcbda44d473 100644
>>>>> --- a/drivers/iommu/Kconfig
>>>>> +++ b/drivers/iommu/Kconfig
>>>>> @@ -508,8 +508,9 @@ config HYPERV_IOMMU
>>>>>    config VIRTIO_IOMMU
>>>>>    	bool "Virtio IOMMU driver"
>>>>>    	depends on VIRTIO=y
>>>>> -	depends on ARM64
>>>>> +	depends on (ARM64 || X86)
>>>>>    	select IOMMU_API
>>>>> +	select IOMMU_DMA
>>>>
>>>> Can that have an "if X86" for clarity? AIUI it's not necessary for
>>>> virtio-iommu itself (and really shouldn't be), but is merely to satisfy the
>>>> x86 arch code's expectation that IOMMU drivers bring their own DMA ops,
>>>> right?
>>>>
>>>> Robin.
>>>
>>> In fact does not this work on any platform now?
>>
>> There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU
>> has been converted recently [1] but VT-d still implements its own DMA ops
>> (conversion patches are on the list [2]). On Arm the arch Kconfig selects
>> IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is
>> complete. Until then I can add a "if X86" here for clarity.
>>
>> Thanks,
>> Jean
>>
>> [1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/
>> [2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/
> 
> What about others? E.g. PPC?

That was the point I was getting at - while iommu-dma should build just 
fine for the likes of PPC, s390, 32-bit Arm, etc., they have no 
architecture code to correctly wire up iommu_dma_ops to devices. Thus 
there's currently no point pulling it in and pretending it's anything 
more than a waste of space for architectures other than arm64 and x86. 
It's merely a historical artefact of the x86 DMA API implementation that 
when the IOMMU drivers were split out to form drivers/iommu they took 
some of their relevant arch code with them.

Robin.
Michael S. Tsirkin Feb. 17, 2020, 1:31 p.m. UTC | #5
On Mon, Feb 17, 2020 at 01:22:44PM +0000, Robin Murphy wrote:
> On 17/02/2020 1:01 pm, Michael S. Tsirkin wrote:
> > On Mon, Feb 17, 2020 at 10:01:07AM +0100, Jean-Philippe Brucker wrote:
> > > On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote:
> > > > On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote:
> > > > > On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote:
> > > > > > With the built-in topology description in place, x86 platforms can now
> > > > > > use the virtio-iommu.
> > > > > > 
> > > > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > > > > > ---
> > > > > >    drivers/iommu/Kconfig | 3 ++-
> > > > > >    1 file changed, 2 insertions(+), 1 deletion(-)
> > > > > > 
> > > > > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > > > > > index 068d4e0e3541..adcbda44d473 100644
> > > > > > --- a/drivers/iommu/Kconfig
> > > > > > +++ b/drivers/iommu/Kconfig
> > > > > > @@ -508,8 +508,9 @@ config HYPERV_IOMMU
> > > > > >    config VIRTIO_IOMMU
> > > > > >    	bool "Virtio IOMMU driver"
> > > > > >    	depends on VIRTIO=y
> > > > > > -	depends on ARM64
> > > > > > +	depends on (ARM64 || X86)
> > > > > >    	select IOMMU_API
> > > > > > +	select IOMMU_DMA
> > > > > 
> > > > > Can that have an "if X86" for clarity? AIUI it's not necessary for
> > > > > virtio-iommu itself (and really shouldn't be), but is merely to satisfy the
> > > > > x86 arch code's expectation that IOMMU drivers bring their own DMA ops,
> > > > > right?
> > > > > 
> > > > > Robin.
> > > > 
> > > > In fact does not this work on any platform now?
> > > 
> > > There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU
> > > has been converted recently [1] but VT-d still implements its own DMA ops
> > > (conversion patches are on the list [2]). On Arm the arch Kconfig selects
> > > IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is
> > > complete. Until then I can add a "if X86" here for clarity.
> > > 
> > > Thanks,
> > > Jean
> > > 
> > > [1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/
> > > [2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/
> > 
> > What about others? E.g. PPC?
> 
> That was the point I was getting at - while iommu-dma should build just fine
> for the likes of PPC, s390, 32-bit Arm, etc., they have no architecture code
> to correctly wire up iommu_dma_ops to devices. Thus there's currently no
> point pulling it in and pretending it's anything more than a waste of space
> for architectures other than arm64 and x86. It's merely a historical
> artefact of the x86 DMA API implementation that when the IOMMU drivers were
> split out to form drivers/iommu they took some of their relevant arch code
> with them.
> 
> Robin.


Rather than white-listing architectures, how about making the
architectures in question set some kind of symbol, and depend on it?
Robin Murphy Feb. 17, 2020, 2:10 p.m. UTC | #6
On 17/02/2020 1:31 pm, Michael S. Tsirkin wrote:
> On Mon, Feb 17, 2020 at 01:22:44PM +0000, Robin Murphy wrote:
>> On 17/02/2020 1:01 pm, Michael S. Tsirkin wrote:
>>> On Mon, Feb 17, 2020 at 10:01:07AM +0100, Jean-Philippe Brucker wrote:
>>>> On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote:
>>>>> On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote:
>>>>>> On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote:
>>>>>>> With the built-in topology description in place, x86 platforms can now
>>>>>>> use the virtio-iommu.
>>>>>>>
>>>>>>> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
>>>>>>> ---
>>>>>>>     drivers/iommu/Kconfig | 3 ++-
>>>>>>>     1 file changed, 2 insertions(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
>>>>>>> index 068d4e0e3541..adcbda44d473 100644
>>>>>>> --- a/drivers/iommu/Kconfig
>>>>>>> +++ b/drivers/iommu/Kconfig
>>>>>>> @@ -508,8 +508,9 @@ config HYPERV_IOMMU
>>>>>>>     config VIRTIO_IOMMU
>>>>>>>     	bool "Virtio IOMMU driver"
>>>>>>>     	depends on VIRTIO=y
>>>>>>> -	depends on ARM64
>>>>>>> +	depends on (ARM64 || X86)
>>>>>>>     	select IOMMU_API
>>>>>>> +	select IOMMU_DMA
>>>>>>
>>>>>> Can that have an "if X86" for clarity? AIUI it's not necessary for
>>>>>> virtio-iommu itself (and really shouldn't be), but is merely to satisfy the
>>>>>> x86 arch code's expectation that IOMMU drivers bring their own DMA ops,
>>>>>> right?
>>>>>>
>>>>>> Robin.
>>>>>
>>>>> In fact does not this work on any platform now?
>>>>
>>>> There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU
>>>> has been converted recently [1] but VT-d still implements its own DMA ops
>>>> (conversion patches are on the list [2]). On Arm the arch Kconfig selects
>>>> IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is
>>>> complete. Until then I can add a "if X86" here for clarity.
>>>>
>>>> Thanks,
>>>> Jean
>>>>
>>>> [1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/
>>>> [2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/
>>>
>>> What about others? E.g. PPC?
>>
>> That was the point I was getting at - while iommu-dma should build just fine
>> for the likes of PPC, s390, 32-bit Arm, etc., they have no architecture code
>> to correctly wire up iommu_dma_ops to devices. Thus there's currently no
>> point pulling it in and pretending it's anything more than a waste of space
>> for architectures other than arm64 and x86. It's merely a historical
>> artefact of the x86 DMA API implementation that when the IOMMU drivers were
>> split out to form drivers/iommu they took some of their relevant arch code
>> with them.
>>
>> Robin.
> 
> 
> Rather than white-listing architectures, how about making the
> architectures in question set some kind of symbol, and depend on it?

Umm, that's basically what we have already? Architectures that use 
iommu_dma_ops select IOMMU_DMA.

The only issue is the oddity of x86 treating IOMMU drivers as part of 
its arch code, which has never come up against a cross-architecture 
driver until now. Hence the options of either maintaining that paradigm 
and having the 'x86 arch code' aspect of this driver "select IOMMU_DMA 
if x86" such that it works out equivalent to AMD_IOMMU, or a more 
involved cleanup to move that responsibility out of 
drivers/iommu/Kconfig entirely and have arch/x86/Kconfig do something 
like "select IOMMU_DMA if IOMMU_API", as Jean suggested up-thread.

In the specific context of IOMMU_DMA we're not talking about any kind of 
white-list, merely a one-off special case for one particular architecture.

Robin.

Patch
diff mbox series

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 068d4e0e3541..adcbda44d473 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -508,8 +508,9 @@  config HYPERV_IOMMU
 config VIRTIO_IOMMU
 	bool "Virtio IOMMU driver"
 	depends on VIRTIO=y
-	depends on ARM64
+	depends on (ARM64 || X86)
 	select IOMMU_API
+	select IOMMU_DMA
 	select INTERVAL_TREE
 	help
 	  Para-virtualised IOMMU driver with virtio.