[PATCH] PCI: IOV: reread SRIOV_NUM_VF after enabling ARI

[PATCH] PCI: IOV: reread SRIOV_NUM_VF after enabling ARI

[Ben Shelton]

For some SR-IOV devices, the number of available virtual functions
increases after enabling ARI.  Currently, SRIOV_NUM_VF is read and saved
off before the ARI control bit is enabled.  This causes an issue when VFs
are enabled.

At device init, SRIOV_INITIAL_VF and SRIOV_NUM_VF are specified to contain
the number of available VFs for the device.  sriov_enable() does a sanity
check that PCI_SRIOV_INITIAL_VF is not greater than iov->total_VFs, the
saved-off value of SRIOV_NUM_VF.  Since the value of both SRIOV_INITIAL_VF
and SRIOV_NUM_VF has increased after enabling the ARI bit, the check fails,
and the VFs cannot be enabled.

To fix the issue, after ARI is enabled for a device, reread SRIOV_NUM_VF.

Signed-off-by: Ben Shelton <benjamin.h.shelton@intel.com>
---
 drivers/pci/iov.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index ee0ebff..88b1959 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -388,6 +388,7 @@ static int sriov_init(struct pci_dev *dev, int pos)
 	struct pci_sriov *iov;
 	struct resource *res;
 	struct pci_dev *pdev;
+	bool total_needs_reread = false;
 
 	if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_END &&
 	    pci_pcie_type(dev) != PCI_EXP_TYPE_ENDPOINT)
@@ -409,12 +410,18 @@ static int sriov_init(struct pci_dev *dev, int pos)
 			goto found;
 
 	pdev = NULL;
-	if (pci_ari_enabled(dev->bus))
+	if (pci_ari_enabled(dev->bus)) {
 		ctrl |= PCI_SRIOV_CTRL_ARI;
+		total_needs_reread = true;
+	}
 
 found:
 	pci_write_config_word(dev, pos + PCI_SRIOV_CTRL, ctrl);
 	pci_write_config_word(dev, pos + PCI_SRIOV_NUM_VF, 0);
+
+	if (total_needs_reread)
+		pci_read_config_word(dev, pos + PCI_SRIOV_TOTAL_VF, &total);
+
 	pci_read_config_word(dev, pos + PCI_SRIOV_VF_OFFSET, &offset);
 	pci_read_config_word(dev, pos + PCI_SRIOV_VF_STRIDE, &stride);
 	if (!offset || (total > 1 && !stride))
-- 
1.9.5

Re: [PATCH] PCI: IOV: reread SRIOV_NUM_VF after enabling ARI

[Bjorn Helgaas]

Hi Ben,

On Fri, Sep 11, 2015 at 04:55:00PM -0500, Ben Shelton wrote:
> For some SR-IOV devices, the number of available virtual functions
> increases after enabling ARI.  Currently, SRIOV_NUM_VF is read and saved
> off before the ARI control bit is enabled.  This causes an issue when VFs
> are enabled.
> 
> At device init, SRIOV_INITIAL_VF and SRIOV_NUM_VF are specified to contain
> the number of available VFs for the device.  sriov_enable() does a sanity
> check that PCI_SRIOV_INITIAL_VF is not greater than iov->total_VFs, the
> saved-off value of SRIOV_NUM_VF.  Since the value of both SRIOV_INITIAL_VF
> and SRIOV_NUM_VF has increased after enabling the ARI bit, the check fails,
> and the VFs cannot be enabled.
> 
> To fix the issue, after ARI is enabled for a device, reread SRIOV_NUM_VF.
> 
> Signed-off-by: Ben Shelton <benjamin.h.shelton@intel.com>
> ---
>  drivers/pci/iov.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index ee0ebff..88b1959 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -388,6 +388,7 @@ static int sriov_init(struct pci_dev *dev, int pos)
>  	struct pci_sriov *iov;
>  	struct resource *res;
>  	struct pci_dev *pdev;
> +	bool total_needs_reread = false;
>  
>  	if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_END &&
>  	    pci_pcie_type(dev) != PCI_EXP_TYPE_ENDPOINT)
> @@ -409,12 +410,18 @@ static int sriov_init(struct pci_dev *dev, int pos)
>  			goto found;
>  
>  	pdev = NULL;
> -	if (pci_ari_enabled(dev->bus))
> +	if (pci_ari_enabled(dev->bus)) {
>  		ctrl |= PCI_SRIOV_CTRL_ARI;
> +		total_needs_reread = true;
> +	}
>  
>  found:
>  	pci_write_config_word(dev, pos + PCI_SRIOV_CTRL, ctrl);
>  	pci_write_config_word(dev, pos + PCI_SRIOV_NUM_VF, 0);
> +
> +	if (total_needs_reread)
> +		pci_read_config_word(dev, pos + PCI_SRIOV_TOTAL_VF, &total);

Can we just *move* the PCI_SRIOV_TOTAL_VF read from its original
location and do it unconditionally here?  I don't think we use "total"
for anything in the interim, and it'd be nice if we could do this
without the "total_needs_reread" flag.

>  	pci_read_config_word(dev, pos + PCI_SRIOV_VF_OFFSET, &offset);
>  	pci_read_config_word(dev, pos + PCI_SRIOV_VF_STRIDE, &stride);
>  	if (!offset || (total > 1 && !stride))
> -- 
> 1.9.5
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH] PCI: IOV: reread SRIOV_NUM_VF after enabling ARI

[Ben Shelton]

Hi Bjorn,

On Wed, Oct 07, 2015 at 02:29:40PM -0500, Bjorn Helgaas wrote:
> Hi Ben,
> 
> On Fri, Sep 11, 2015 at 04:55:00PM -0500, Ben Shelton wrote:
> > For some SR-IOV devices, the number of available virtual functions
> > increases after enabling ARI.  Currently, SRIOV_NUM_VF is read and saved
> > off before the ARI control bit is enabled.  This causes an issue when VFs
> > are enabled.
> > 
> > At device init, SRIOV_INITIAL_VF and SRIOV_NUM_VF are specified to contain
> > the number of available VFs for the device.  sriov_enable() does a sanity
> > check that PCI_SRIOV_INITIAL_VF is not greater than iov->total_VFs, the
> > saved-off value of SRIOV_NUM_VF.  Since the value of both SRIOV_INITIAL_VF
> > and SRIOV_NUM_VF has increased after enabling the ARI bit, the check fails,
> > and the VFs cannot be enabled.
> > 
> > To fix the issue, after ARI is enabled for a device, reread SRIOV_NUM_VF.
> > 
> > Signed-off-by: Ben Shelton <benjamin.h.shelton@intel.com>
> > ---
> >  drivers/pci/iov.c | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> > index ee0ebff..88b1959 100644
> > --- a/drivers/pci/iov.c
> > +++ b/drivers/pci/iov.c
> > @@ -388,6 +388,7 @@ static int sriov_init(struct pci_dev *dev, int pos)
> >  	struct pci_sriov *iov;
> >  	struct resource *res;
> >  	struct pci_dev *pdev;
> > +	bool total_needs_reread = false;
> >  
> >  	if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_END &&
> >  	    pci_pcie_type(dev) != PCI_EXP_TYPE_ENDPOINT)
> > @@ -409,12 +410,18 @@ static int sriov_init(struct pci_dev *dev, int pos)
> >  			goto found;
> >  
> >  	pdev = NULL;
> > -	if (pci_ari_enabled(dev->bus))
> > +	if (pci_ari_enabled(dev->bus)) {
> >  		ctrl |= PCI_SRIOV_CTRL_ARI;
> > +		total_needs_reread = true;
> > +	}
> >  
> >  found:
> >  	pci_write_config_word(dev, pos + PCI_SRIOV_CTRL, ctrl);
> >  	pci_write_config_word(dev, pos + PCI_SRIOV_NUM_VF, 0);
> > +
> > +	if (total_needs_reread)
> > +		pci_read_config_word(dev, pos + PCI_SRIOV_TOTAL_VF, &total);
> 
> Can we just *move* the PCI_SRIOV_TOTAL_VF read from its original
> location and do it unconditionally here?  I don't think we use "total"
> for anything in the interim, and it'd be nice if we could do this
> without the "total_needs_reread" flag.

The only thing we do with 'total' is return early if it's read as 0
(i.e. for a device that does not support any VFs).  If we just move the
read to here, a PCI device with no VFs would have its PCI_SRIOV_CTRL
config word written before PCI_SRIOV_TOTAL_VF is read as 0 and
sriov_init() returns.  The reread preserves the original behavior.

If the change in behavior is OK, I'll make the change and submit a v2.

Thanks,
Ben

> 
> >  	pci_read_config_word(dev, pos + PCI_SRIOV_VF_OFFSET, &offset);
> >  	pci_read_config_word(dev, pos + PCI_SRIOV_VF_STRIDE, &stride);
> >  	if (!offset || (total > 1 && !stride))
> > -- 
> > 1.9.5
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH] PCI: IOV: reread SRIOV_NUM_VF after enabling ARI

[Bjorn Helgaas]

On Wed, Oct 07, 2015 at 03:21:36PM -0500, Ben Shelton wrote:
> Hi Bjorn,
> 
> On Wed, Oct 07, 2015 at 02:29:40PM -0500, Bjorn Helgaas wrote:
> > Hi Ben,
> > 
> > On Fri, Sep 11, 2015 at 04:55:00PM -0500, Ben Shelton wrote:
> > > For some SR-IOV devices, the number of available virtual functions
> > > increases after enabling ARI.  Currently, SRIOV_NUM_VF is read and saved
> > > off before the ARI control bit is enabled.  This causes an issue when VFs
> > > are enabled.
> > > 
> > > At device init, SRIOV_INITIAL_VF and SRIOV_NUM_VF are specified to contain
> > > the number of available VFs for the device.  sriov_enable() does a sanity
> > > check that PCI_SRIOV_INITIAL_VF is not greater than iov->total_VFs, the
> > > saved-off value of SRIOV_NUM_VF.  Since the value of both SRIOV_INITIAL_VF
> > > and SRIOV_NUM_VF has increased after enabling the ARI bit, the check fails,
> > > and the VFs cannot be enabled.
> > > 
> > > To fix the issue, after ARI is enabled for a device, reread SRIOV_NUM_VF.
> > > 
> > > Signed-off-by: Ben Shelton <benjamin.h.shelton@intel.com>
> > > ---
> > >  drivers/pci/iov.c | 9 ++++++++-
> > >  1 file changed, 8 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> > > index ee0ebff..88b1959 100644
> > > --- a/drivers/pci/iov.c
> > > +++ b/drivers/pci/iov.c
> > > @@ -388,6 +388,7 @@ static int sriov_init(struct pci_dev *dev, int pos)
> > >  	struct pci_sriov *iov;
> > >  	struct resource *res;
> > >  	struct pci_dev *pdev;
> > > +	bool total_needs_reread = false;
> > >  
> > >  	if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_END &&
> > >  	    pci_pcie_type(dev) != PCI_EXP_TYPE_ENDPOINT)
> > > @@ -409,12 +410,18 @@ static int sriov_init(struct pci_dev *dev, int pos)
> > >  			goto found;
> > >  
> > >  	pdev = NULL;
> > > -	if (pci_ari_enabled(dev->bus))
> > > +	if (pci_ari_enabled(dev->bus)) {
> > >  		ctrl |= PCI_SRIOV_CTRL_ARI;
> > > +		total_needs_reread = true;
> > > +	}
> > >  
> > >  found:
> > >  	pci_write_config_word(dev, pos + PCI_SRIOV_CTRL, ctrl);
> > >  	pci_write_config_word(dev, pos + PCI_SRIOV_NUM_VF, 0);
> > > +
> > > +	if (total_needs_reread)
> > > +		pci_read_config_word(dev, pos + PCI_SRIOV_TOTAL_VF, &total);
> > 
> > Can we just *move* the PCI_SRIOV_TOTAL_VF read from its original
> > location and do it unconditionally here?  I don't think we use "total"
> > for anything in the interim, and it'd be nice if we could do this
> > without the "total_needs_reread" flag.
> 
> The only thing we do with 'total' is return early if it's read as 0
> (i.e. for a device that does not support any VFs).  If we just move the
> read to here, a PCI device with no VFs would have its PCI_SRIOV_CTRL
> config word written before PCI_SRIOV_TOTAL_VF is read as 0 and
> sriov_init() returns.  The reread preserves the original behavior.
> 
> If the change in behavior is OK, I'll make the change and submit a v2.

I think that's OK.  We do return some other errors after modifying
PCI_SRIOV_CTRL, so I don't know that this would be any worse.

Bjorn