[PATCH v2 1/1] PCI/IOV: Fix incorrect cfg_size for VF > 0

[PATCH v2 1/1] PCI/IOV: Fix incorrect cfg_size for VF > 0

[sathyanarayanan.kuppuswamy]

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Commit 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
other VFs") calculates and caches the cfg_size for VF0 device before
initializing the pcie_cap of the device which results in using incorrect
cfg_size for all VF devices > 0. So set pcie_cap of the device before
calculating the cfg_size of VF0 device.

Fixes: 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
other VFs")
Cc: Ashok Raj <ashok.raj@intel.com>
Suggested-by: Mike Campin <mike.campin@intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---

Changes since v1:
 * Fixed a typo in commit message.

 drivers/pci/iov.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 3aa115ed3a65..2869011c0e35 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -160,6 +160,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
 	virtfn->device = iov->vf_device;
 	virtfn->is_virtfn = 1;
 	virtfn->physfn = pci_dev_get(dev);
+	virtfn->pcie_cap = pci_find_capability(virtfn, PCI_CAP_ID_EXP);
 
 	if (id == 0)
 		pci_read_vf_config_common(virtfn);
-- 
2.21.0

Re: [PATCH v2 1/1] PCI/IOV: Fix incorrect cfg_size for VF > 0

[Myron Stowe]

This looks to basically be a duplicate of what Alex Williamson posted
8 days ago: https://lore.kernel.org/linux-pci/20190604143617.0a226555@x1.home/
Alex says Hao Zheng had a similar patch as well.

On Wed, Jun 12, 2019 at 12:08 PM
<sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
>
> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>
> Commit 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> other VFs") calculates and caches the cfg_size for VF0 device before
> initializing the pcie_cap of the device which results in using incorrect
> cfg_size for all VF devices > 0. So set pcie_cap of the device before
> calculating the cfg_size of VF0 device.
>
> Fixes: 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> other VFs")
> Cc: Ashok Raj <ashok.raj@intel.com>
> Suggested-by: Mike Campin <mike.campin@intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> ---
>
> Changes since v1:
>  * Fixed a typo in commit message.
>
>  drivers/pci/iov.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 3aa115ed3a65..2869011c0e35 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -160,6 +160,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
>         virtfn->device = iov->vf_device;
>         virtfn->is_virtfn = 1;
>         virtfn->physfn = pci_dev_get(dev);
> +       virtfn->pcie_cap = pci_find_capability(virtfn, PCI_CAP_ID_EXP);
>
>         if (id == 0)
>                 pci_read_vf_config_common(virtfn);
> --
> 2.21.0
>

Re: [PATCH v2 1/1] PCI/IOV: Fix incorrect cfg_size for VF > 0

[Alex Williamson]

On Wed, 12 Jun 2019 10:06:47 -0700
sathyanarayanan.kuppuswamy@linux.intel.com wrote:

> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> 
> Commit 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> other VFs") calculates and caches the cfg_size for VF0 device before
> initializing the pcie_cap of the device which results in using incorrect
> cfg_size for all VF devices > 0. So set pcie_cap of the device before
> calculating the cfg_size of VF0 device.
> 
> Fixes: 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> other VFs")
> Cc: Ashok Raj <ashok.raj@intel.com>
> Suggested-by: Mike Campin <mike.campin@intel.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> ---
> 
> Changes since v1:
>  * Fixed a typo in commit message.
> 
>  drivers/pci/iov.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 3aa115ed3a65..2869011c0e35 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -160,6 +160,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
>  	virtfn->device = iov->vf_device;
>  	virtfn->is_virtfn = 1;
>  	virtfn->physfn = pci_dev_get(dev);
> +	virtfn->pcie_cap = pci_find_capability(virtfn, PCI_CAP_ID_EXP);
>  
>  	if (id == 0)
>  		pci_read_vf_config_common(virtfn);

Why not re-order until after we've setup pcie_cap?

https://lore.kernel.org/linux-pci/20190604143617.0a226555@x1.home/T/#

Thanks,
Alex

Re: [PATCH v2 1/1] PCI/IOV: Fix incorrect cfg_size for VF > 0

[sathyanarayanan kuppuswamy]

On 6/12/19 11:19 AM, Alex Williamson wrote:
> On Wed, 12 Jun 2019 10:06:47 -0700
> sathyanarayanan.kuppuswamy@linux.intel.com wrote:
>
>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>>
>> Commit 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
>> other VFs") calculates and caches the cfg_size for VF0 device before
>> initializing the pcie_cap of the device which results in using incorrect
>> cfg_size for all VF devices > 0. So set pcie_cap of the device before
>> calculating the cfg_size of VF0 device.
>>
>> Fixes: 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
>> other VFs")
>> Cc: Ashok Raj <ashok.raj@intel.com>
>> Suggested-by: Mike Campin <mike.campin@intel.com>
>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>> ---
>>
>> Changes since v1:
>>   * Fixed a typo in commit message.
>>
>>   drivers/pci/iov.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
>> index 3aa115ed3a65..2869011c0e35 100644
>> --- a/drivers/pci/iov.c
>> +++ b/drivers/pci/iov.c
>> @@ -160,6 +160,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
>>   	virtfn->device = iov->vf_device;
>>   	virtfn->is_virtfn = 1;
>>   	virtfn->physfn = pci_dev_get(dev);
>> +	virtfn->pcie_cap = pci_find_capability(virtfn, PCI_CAP_ID_EXP);
>>   
>>   	if (id == 0)
>>   		pci_read_vf_config_common(virtfn);
> Why not re-order until after we've setup pcie_cap?
>
> https://lore.kernel.org/linux-pci/20190604143617.0a226555@x1.home/T/#

pci_read_vf_config_common() also caches values for properties like 
class, hdr_type, susbsystem_vendor/device. These values are read/used in 
pci_setup_device(). So if we can use cached values in 
pci_setup_device(), we don't have to read them from registers twice for 
each device.

>
> Thanks,
> Alex
>
-- 
Sathyanarayanan Kuppuswamy
Linux kernel developer

Re: [PATCH v2 1/1] PCI/IOV: Fix incorrect cfg_size for VF > 0

[Alex Williamson]

On Wed, 12 Jun 2019 11:41:36 -0700
sathyanarayanan kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>
wrote:

> On 6/12/19 11:19 AM, Alex Williamson wrote:
> > On Wed, 12 Jun 2019 10:06:47 -0700
> > sathyanarayanan.kuppuswamy@linux.intel.com wrote:
> >  
> >> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> >>
> >> Commit 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> >> other VFs") calculates and caches the cfg_size for VF0 device before
> >> initializing the pcie_cap of the device which results in using incorrect
> >> cfg_size for all VF devices > 0. So set pcie_cap of the device before
> >> calculating the cfg_size of VF0 device.
> >>
> >> Fixes: 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> >> other VFs")
> >> Cc: Ashok Raj <ashok.raj@intel.com>
> >> Suggested-by: Mike Campin <mike.campin@intel.com>
> >> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> >> ---
> >>
> >> Changes since v1:
> >>   * Fixed a typo in commit message.
> >>
> >>   drivers/pci/iov.c | 1 +
> >>   1 file changed, 1 insertion(+)
> >>
> >> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> >> index 3aa115ed3a65..2869011c0e35 100644
> >> --- a/drivers/pci/iov.c
> >> +++ b/drivers/pci/iov.c
> >> @@ -160,6 +160,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
> >>   	virtfn->device = iov->vf_device;
> >>   	virtfn->is_virtfn = 1;
> >>   	virtfn->physfn = pci_dev_get(dev);
> >> +	virtfn->pcie_cap = pci_find_capability(virtfn, PCI_CAP_ID_EXP);
> >>   
> >>   	if (id == 0)
> >>   		pci_read_vf_config_common(virtfn);  
> > Why not re-order until after we've setup pcie_cap?
> >
> > https://lore.kernel.org/linux-pci/20190604143617.0a226555@x1.home/T/#  
> 
> pci_read_vf_config_common() also caches values for properties like 
> class, hdr_type, susbsystem_vendor/device. These values are read/used in 
> pci_setup_device(). So if we can use cached values in 
> pci_setup_device(), we don't have to read them from registers twice for 
> each device.

Sorry, I missed that dependency, a bit too subtle.  It's still pretty
ugly that pci_setup_device()->set_pcie_port_type() is the canonical
location for setting pcie_cap and now we need to kludge it earlier.
What about the question in the self follow-up to my patch in the link
above, can we simply assume 4K config space on a VF?  Thanks,

Alex

Re: [PATCH v2 1/1] PCI/IOV: Fix incorrect cfg_size for VF > 0

[Raj, Ashok]

On Wed, Jun 12, 2019 at 12:58:17PM -0600, Alex Williamson wrote:
> On Wed, 12 Jun 2019 11:41:36 -0700
> sathyanarayanan kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>
> wrote:
> 
> > On 6/12/19 11:19 AM, Alex Williamson wrote:
> > > On Wed, 12 Jun 2019 10:06:47 -0700
> > > sathyanarayanan.kuppuswamy@linux.intel.com wrote:
> > >  
> > >> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > >>
> > >> Commit 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> > >> other VFs") calculates and caches the cfg_size for VF0 device before
> > >> initializing the pcie_cap of the device which results in using incorrect
> > >> cfg_size for all VF devices > 0. So set pcie_cap of the device before
> > >> calculating the cfg_size of VF0 device.
> > >>
> > >> Fixes: 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> > >> other VFs")
> > >> Cc: Ashok Raj <ashok.raj@intel.com>
> > >> Suggested-by: Mike Campin <mike.campin@intel.com>
> > >> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > >> ---
> > >>
> > >> Changes since v1:
> > >>   * Fixed a typo in commit message.
> > >>
> > >>   drivers/pci/iov.c | 1 +
> > >>   1 file changed, 1 insertion(+)
> > >>
> > >> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> > >> index 3aa115ed3a65..2869011c0e35 100644
> > >> --- a/drivers/pci/iov.c
> > >> +++ b/drivers/pci/iov.c
> > >> @@ -160,6 +160,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
> > >>   	virtfn->device = iov->vf_device;
> > >>   	virtfn->is_virtfn = 1;
> > >>   	virtfn->physfn = pci_dev_get(dev);
> > >> +	virtfn->pcie_cap = pci_find_capability(virtfn, PCI_CAP_ID_EXP);
> > >>   
> > >>   	if (id == 0)
> > >>   		pci_read_vf_config_common(virtfn);  
> > > Why not re-order until after we've setup pcie_cap?
> > >
> > > https://lore.kernel.org/linux-pci/20190604143617.0a226555@x1.home/T/#  
> > 
> > pci_read_vf_config_common() also caches values for properties like 
> > class, hdr_type, susbsystem_vendor/device. These values are read/used in 
> > pci_setup_device(). So if we can use cached values in 
> > pci_setup_device(), we don't have to read them from registers twice for 
> > each device.
> 
> Sorry, I missed that dependency, a bit too subtle.  It's still pretty
> ugly that pci_setup_device()->set_pcie_port_type() is the canonical
> location for setting pcie_cap and now we need to kludge it earlier.
> What about the question in the self follow-up to my patch in the link
> above, can we simply assume 4K config space on a VF?  Thanks,

There should be no issue simply reading them once? I don't know
what that exact optimization saves, unless some broken VFs didn't
actually expose all the capabilities in config space and this happens
to workaround the problem.

+ Karim

Cheers,
Ashok

Re: [PATCH v2 1/1] PCI/IOV: Fix incorrect cfg_size for VF > 0

[Alex Williamson]

On Wed, 12 Jun 2019 12:03:03 -0700
"Raj, Ashok" <ashok.raj@intel.com> wrote:

> On Wed, Jun 12, 2019 at 12:58:17PM -0600, Alex Williamson wrote:
> > On Wed, 12 Jun 2019 11:41:36 -0700
> > sathyanarayanan kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>
> > wrote:
> >   
> > > On 6/12/19 11:19 AM, Alex Williamson wrote:  
> > > > On Wed, 12 Jun 2019 10:06:47 -0700
> > > > sathyanarayanan.kuppuswamy@linux.intel.com wrote:
> > > >    
> > > >> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > > >>
> > > >> Commit 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> > > >> other VFs") calculates and caches the cfg_size for VF0 device before
> > > >> initializing the pcie_cap of the device which results in using incorrect
> > > >> cfg_size for all VF devices > 0. So set pcie_cap of the device before
> > > >> calculating the cfg_size of VF0 device.
> > > >>
> > > >> Fixes: 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> > > >> other VFs")
> > > >> Cc: Ashok Raj <ashok.raj@intel.com>
> > > >> Suggested-by: Mike Campin <mike.campin@intel.com>
> > > >> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > > >> ---
> > > >>
> > > >> Changes since v1:
> > > >>   * Fixed a typo in commit message.
> > > >>
> > > >>   drivers/pci/iov.c | 1 +
> > > >>   1 file changed, 1 insertion(+)
> > > >>
> > > >> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> > > >> index 3aa115ed3a65..2869011c0e35 100644
> > > >> --- a/drivers/pci/iov.c
> > > >> +++ b/drivers/pci/iov.c
> > > >> @@ -160,6 +160,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
> > > >>   	virtfn->device = iov->vf_device;
> > > >>   	virtfn->is_virtfn = 1;
> > > >>   	virtfn->physfn = pci_dev_get(dev);
> > > >> +	virtfn->pcie_cap = pci_find_capability(virtfn, PCI_CAP_ID_EXP);
> > > >>   
> > > >>   	if (id == 0)
> > > >>   		pci_read_vf_config_common(virtfn);    
> > > > Why not re-order until after we've setup pcie_cap?
> > > >
> > > > https://lore.kernel.org/linux-pci/20190604143617.0a226555@x1.home/T/#    
> > > 
> > > pci_read_vf_config_common() also caches values for properties like 
> > > class, hdr_type, susbsystem_vendor/device. These values are read/used in 
> > > pci_setup_device(). So if we can use cached values in 
> > > pci_setup_device(), we don't have to read them from registers twice for 
> > > each device.  
> > 
> > Sorry, I missed that dependency, a bit too subtle.  It's still pretty
> > ugly that pci_setup_device()->set_pcie_port_type() is the canonical
> > location for setting pcie_cap and now we need to kludge it earlier.
> > What about the question in the self follow-up to my patch in the link
> > above, can we simply assume 4K config space on a VF?  Thanks,  
> 
> There should be no issue simply reading them once? I don't know
> what that exact optimization saves, unless some broken VFs didn't
> actually expose all the capabilities in config space and this happens
> to workaround the problem.

AIUI the original commit only saves us a few config space reads for VFs
after the first where we test that extended config space is available
and not simply an alias of standard config space.  Thanks,

Alex

Re: [PATCH v2 1/1] PCI/IOV: Fix incorrect cfg_size for VF > 0

[Raslan, KarimAllah]

On Wed, 2019-06-12 at 12:03 -0700, Raj, Ashok wrote:
> On Wed, Jun 12, 2019 at 12:58:17PM -0600, Alex Williamson wrote:
> > 
> > On Wed, 12 Jun 2019 11:41:36 -0700
> > sathyanarayanan kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>
> > wrote:
> > 
> > > 
> > > On 6/12/19 11:19 AM, Alex Williamson wrote:
> > > > 
> > > > On Wed, 12 Jun 2019 10:06:47 -0700
> > > > sathyanarayanan.kuppuswamy@linux.intel.com wrote:
> > > >  
> > > > > 
> > > > > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > > > > 
> > > > > Commit 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> > > > > other VFs") calculates and caches the cfg_size for VF0 device before
> > > > > initializing the pcie_cap of the device which results in using incorrect
> > > > > cfg_size for all VF devices > 0. So set pcie_cap of the device before
> > > > > calculating the cfg_size of VF0 device.
> > > > > 
> > > > > Fixes: 975bb8b4dc93 ("PCI/IOV: Use VF0 cached config space size for
> > > > > other VFs")
> > > > > Cc: Ashok Raj <ashok.raj@intel.com>
> > > > > Suggested-by: Mike Campin <mike.campin@intel.com>
> > > > > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> > > > > ---
> > > > > 
> > > > > Changes since v1:
> > > > >   * Fixed a typo in commit message.
> > > > > 
> > > > >   drivers/pci/iov.c | 1 +
> > > > >   1 file changed, 1 insertion(+)
> > > > > 
> > > > > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> > > > > index 3aa115ed3a65..2869011c0e35 100644
> > > > > --- a/drivers/pci/iov.c
> > > > > +++ b/drivers/pci/iov.c
> > > > > @@ -160,6 +160,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
> > > > >   	virtfn->device = iov->vf_device;
> > > > >   	virtfn->is_virtfn = 1;
> > > > >   	virtfn->physfn = pci_dev_get(dev);
> > > > > +	virtfn->pcie_cap = pci_find_capability(virtfn, PCI_CAP_ID_EXP);
> > > > >   
> > > > >   	if (id == 0)
> > > > >   		pci_read_vf_config_common(virtfn);  
> > > > Why not re-order until after we've setup pcie_cap?
> > > > 
> > > > https://lore.kernel.org/linux-pci/20190604143617.0a226555@x1.home/T/#  
> > > 
> > > pci_read_vf_config_common() also caches values for properties like 
> > > class, hdr_type, susbsystem_vendor/device. These values are read/used in 
> > > pci_setup_device(). So if we can use cached values in 
> > > pci_setup_device(), we don't have to read them from registers twice for 
> > > each device.
> > 
> > Sorry, I missed that dependency, a bit too subtle.  It's still pretty
> > ugly that pci_setup_device()->set_pcie_port_type() is the canonical
> > location for setting pcie_cap and now we need to kludge it earlier.
> > What about the question in the self follow-up to my patch in the link
> > above, can we simply assume 4K config space on a VF?  Thanks,
> 
> There should be no issue simply reading them once? I don't know
> what that exact optimization saves, unless some broken VFs didn't
> actually expose all the capabilities in config space and this happens
> to workaround the problem.

The original patch was to save time when you have hundreds of VFs in the system 
and doing this for each one of them is just a waste of time.

> 
> + Karim
> 
> Cheers,
> Ashok



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