[PATCH v3 1/8] PCI/IOV: Return unsigned int from pci_sriov_get_totalvfs()

[PATCH v3 1/8] PCI/IOV: Return unsigned int from pci_sriov_get_totalvfs()

[Zhi Wang]

pci_sriov_get_totalvfs() reports a VF count, not an errno-style
status. It returns 0 when SR-IOV is unavailable or the device is not a
PF, and otherwise returns the PF's driver_max_VFs value.

driver_max_VFs is stored as a u16 in struct pci_sriov. It is derived
from the SR-IOV TotalVFs field or from a driver-provided limit, so the
implementation cannot return a negative value.

Change the declaration, CONFIG_PCI_IOV stub, and implementation to
return unsigned int.

Suggested-by: Alexandre Courbot <acourbot@nvidia.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: David Laight <david.laight.linux@gmail.com>
Cc: Gary Guo <gary@garyguo.net>
Cc: linux-pci@vger.kernel.org
Link: https://lore.kernel.org/all/DJHPRE4TGGT8.BUTMYOF5YE05@nvidia.com/
Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 drivers/pci/iov.c   | 2 +-
 include/linux/pci.h | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index b0d24839c084..9d408fb8ac25 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -1283,7 +1283,7 @@ EXPORT_SYMBOL_GPL(pci_sriov_set_totalvfs);
  * SRIOV capability value of TotalVFs or the value of driver_max_VFs
  * if the driver reduced it.  Otherwise 0.
  */
-int pci_sriov_get_totalvfs(struct pci_dev *dev)
+unsigned int pci_sriov_get_totalvfs(struct pci_dev *dev)
 {
 	if (!dev->is_physfn)
 		return 0;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index ebb5b9d76360..2b9c61de5f67 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -2569,7 +2569,7 @@ void pci_iov_remove_virtfn(struct pci_dev *dev, int id);
 int pci_num_vf(struct pci_dev *dev);
 int pci_vfs_assigned(struct pci_dev *dev);
 int pci_sriov_set_totalvfs(struct pci_dev *dev, u16 numvfs);
-int pci_sriov_get_totalvfs(struct pci_dev *dev);
+unsigned int pci_sriov_get_totalvfs(struct pci_dev *dev);
 int pci_sriov_configure_simple(struct pci_dev *dev, int nr_virtfn);
 resource_size_t pci_iov_resource_size(const struct pci_dev *dev, int resno);
 int pci_iov_vf_bar_set_size(struct pci_dev *dev, int resno, int size);
@@ -2622,7 +2622,7 @@ static inline int pci_vfs_assigned(struct pci_dev *dev)
 { return 0; }
 static inline int pci_sriov_set_totalvfs(struct pci_dev *dev, u16 numvfs)
 { return 0; }
-static inline int pci_sriov_get_totalvfs(struct pci_dev *dev)
+static inline unsigned int pci_sriov_get_totalvfs(struct pci_dev *dev)
 { return 0; }
 #define pci_sriov_configure_simple	NULL
 static inline resource_size_t pci_iov_resource_size(const struct pci_dev *dev,
-- 
2.51.0

[PATCH v3 2/8] rust: pci: add sriov_get_totalvfs() helper

[Zhi Wang]

Expose pci_sriov_get_totalvfs() to Rust PCI drivers so they can query
how many SR-IOV VFs a device supports.

Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: David Laight <david.laight.linux@gmail.com>
Cc: Gary Guo <gary@garyguo.net>
Cc: linux-pci@vger.kernel.org
Link: https://lore.kernel.org/all/DJHPRE4TGGT8.BUTMYOF5YE05@nvidia.com/
Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
 rust/kernel/pci.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 5071cae6543f..21c51981c02e 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -450,6 +450,17 @@ pub fn pci_class(&self) -> Class {
         // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
         Class::from_raw(unsafe { (*self.as_raw()).class })
     }
+
+    /// Returns the total number of VFs, or 0 if SR-IOV is not available.
+    #[inline]
+    pub fn sriov_get_totalvfs(&self) -> u16 {
+        // SAFETY: `self.as_raw()` is a valid pointer to a `struct pci_dev`.
+        let total_vfs = unsafe { bindings::pci_sriov_get_totalvfs(self.as_raw()) };
+
+        // CAST: The C helper returns `unsigned int`, but the value originates
+        // from TotalVFs/driver_max_VFs, so this cast cannot truncate.
+        total_vfs as u16
+    }
 }
 
 impl<'a> Device<device::Core<'a>> {
-- 
2.51.0

Re: [PATCH v3 1/8] PCI/IOV: Return unsigned int from pci_sriov_get_totalvfs()

[Alexandre Courbot]

On Wed Jul 1, 2026 at 3:26 PM JST, Zhi Wang wrote:
> pci_sriov_get_totalvfs() reports a VF count, not an errno-style
> status. It returns 0 when SR-IOV is unavailable or the device is not a
> PF, and otherwise returns the PF's driver_max_VFs value.
>
> driver_max_VFs is stored as a u16 in struct pci_sriov. It is derived
> from the SR-IOV TotalVFs field or from a driver-provided limit, so the
> implementation cannot return a negative value.
>
> Change the declaration, CONFIG_PCI_IOV stub, and implementation to
> return unsigned int.
>
> Suggested-by: Alexandre Courbot <acourbot@nvidia.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: David Laight <david.laight.linux@gmail.com>
> Cc: Gary Guo <gary@garyguo.net>
> Cc: linux-pci@vger.kernel.org
> Link: https://lore.kernel.org/all/DJHPRE4TGGT8.BUTMYOF5YE05@nvidia.com/
> Signed-off-by: Zhi Wang <zhiw@nvidia.com>

FWIW,

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>

Re: [PATCH v3 2/8] rust: pci: add sriov_get_totalvfs() helper

[Alexandre Courbot]

On Wed Jul 1, 2026 at 3:26 PM JST, Zhi Wang wrote:
> Expose pci_sriov_get_totalvfs() to Rust PCI drivers so they can query
> how many SR-IOV VFs a device supports.
>
> Cc: Alexandre Courbot <acourbot@nvidia.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: David Laight <david.laight.linux@gmail.com>
> Cc: Gary Guo <gary@garyguo.net>
> Cc: linux-pci@vger.kernel.org
> Link: https://lore.kernel.org/all/DJHPRE4TGGT8.BUTMYOF5YE05@nvidia.com/
> Signed-off-by: Zhi Wang <zhiw@nvidia.com>
> ---
>  rust/kernel/pci.rs | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index 5071cae6543f..21c51981c02e 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -450,6 +450,17 @@ pub fn pci_class(&self) -> Class {
>          // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
>          Class::from_raw(unsafe { (*self.as_raw()).class })
>      }
> +
> +    /// Returns the total number of VFs, or 0 if SR-IOV is not available.
> +    #[inline]
> +    pub fn sriov_get_totalvfs(&self) -> u16 {
> +        // SAFETY: `self.as_raw()` is a valid pointer to a `struct pci_dev`.
> +        let total_vfs = unsafe { bindings::pci_sriov_get_totalvfs(self.as_raw()) };
> +
> +        // CAST: The C helper returns `unsigned int`, but the value originates
> +        // from TotalVFs/driver_max_VFs, so this cast cannot truncate.

nit: "from TotalVFs/driver_max_VFs (which are defined as `u16`), ..."

With that,

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>

Re: [PATCH v3 2/8] rust: pci: add sriov_get_totalvfs() helper

[Alexandre Courbot]

On Wed Jul 8, 2026 at 11:03 PM JST, Alexandre Courbot wrote:
> On Wed Jul 1, 2026 at 3:26 PM JST, Zhi Wang wrote:
>> Expose pci_sriov_get_totalvfs() to Rust PCI drivers so they can query
>> how many SR-IOV VFs a device supports.
>>
>> Cc: Alexandre Courbot <acourbot@nvidia.com>
>> Cc: Bjorn Helgaas <bhelgaas@google.com>
>> Cc: David Laight <david.laight.linux@gmail.com>
>> Cc: Gary Guo <gary@garyguo.net>
>> Cc: linux-pci@vger.kernel.org
>> Link: https://lore.kernel.org/all/DJHPRE4TGGT8.BUTMYOF5YE05@nvidia.com/
>> Signed-off-by: Zhi Wang <zhiw@nvidia.com>
>> ---
>>  rust/kernel/pci.rs | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>>
>> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
>> index 5071cae6543f..21c51981c02e 100644
>> --- a/rust/kernel/pci.rs
>> +++ b/rust/kernel/pci.rs
>> @@ -450,6 +450,17 @@ pub fn pci_class(&self) -> Class {
>>          // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
>>          Class::from_raw(unsafe { (*self.as_raw()).class })
>>      }
>> +
>> +    /// Returns the total number of VFs, or 0 if SR-IOV is not available.
>> +    #[inline]
>> +    pub fn sriov_get_totalvfs(&self) -> u16 {
>> +        // SAFETY: `self.as_raw()` is a valid pointer to a `struct pci_dev`.
>> +        let total_vfs = unsafe { bindings::pci_sriov_get_totalvfs(self.as_raw()) };
>> +
>> +        // CAST: The C helper returns `unsigned int`, but the value originates
>> +        // from TotalVFs/driver_max_VFs, so this cast cannot truncate.
>
> nit: "from TotalVFs/driver_max_VFs (which are defined as `u16`), ..."
>
> With that,
>
> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>

... with an additional item for thought: in a previous revision [1], I
had raised the question of making the return type
`Option<NonZero<u16>>`, as I think it better encodes "0 if SR-IOV is not
available" - callers are then forced to consider the dichotomy of the
result, and not interpret a particular value as having a special meaning.

OTOH, for all practical purposes 0 VFs also seems to be strictly
equivalent to "SR-IOV is not available", so please take this as a
nit to consider, not a blocker.

[1] https://lore.kernel.org/rust-for-linux/DETDILPA1GFY.27WND0TEC5352@nvidia.com/

Re: [PATCH v3 2/8] rust: pci: add sriov_get_totalvfs() helper

[Alexandre Courbot]

On Wed Jul 8, 2026 at 11:03 PM JST, Alexandre Courbot wrote:
> On Wed Jul 1, 2026 at 3:26 PM JST, Zhi Wang wrote:
>> Expose pci_sriov_get_totalvfs() to Rust PCI drivers so they can query
>> how many SR-IOV VFs a device supports.
>>
>> Cc: Alexandre Courbot <acourbot@nvidia.com>
>> Cc: Bjorn Helgaas <bhelgaas@google.com>
>> Cc: David Laight <david.laight.linux@gmail.com>
>> Cc: Gary Guo <gary@garyguo.net>
>> Cc: linux-pci@vger.kernel.org
>> Link: https://lore.kernel.org/all/DJHPRE4TGGT8.BUTMYOF5YE05@nvidia.com/
>> Signed-off-by: Zhi Wang <zhiw@nvidia.com>
>> ---
>>  rust/kernel/pci.rs | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>>
>> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
>> index 5071cae6543f..21c51981c02e 100644
>> --- a/rust/kernel/pci.rs
>> +++ b/rust/kernel/pci.rs
>> @@ -450,6 +450,17 @@ pub fn pci_class(&self) -> Class {
>>          // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
>>          Class::from_raw(unsafe { (*self.as_raw()).class })
>>      }
>> +
>> +    /// Returns the total number of VFs, or 0 if SR-IOV is not available.
>> +    #[inline]
>> +    pub fn sriov_get_totalvfs(&self) -> u16 {
>> +        // SAFETY: `self.as_raw()` is a valid pointer to a `struct pci_dev`.
>> +        let total_vfs = unsafe { bindings::pci_sriov_get_totalvfs(self.as_raw()) };
>> +
>> +        // CAST: The C helper returns `unsigned int`, but the value originates
>> +        // from TotalVFs/driver_max_VFs, so this cast cannot truncate.
>
> nit: "from TotalVFs/driver_max_VFs (which are defined as `u16`), ..."
>
> With that,
>
> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>

Sorry, need to take my tag back. :( Build is failing if `CONFIG_PCI_IOV`
is not set:

    error[E0425]: cannot find function `pci_sriov_get_totalvfs` in crate `bindings`
      --> ../rust/kernel/pci.rs:458:44
        |
    458 |         let total_vfs = unsafe { bindings::pci_sriov_get_totalvfs(self.as_raw()) };
        |                                            ^^^^^^^^^^^^^^^^^^^^^^ not found in `bindings`

Looks like you need to add a helper in `rust/helpers/pci.c` as the
inline C function used when `CONFIG_PCI_IOV` is not set can not be
invoked by Rust.

Re: [PATCH v3 2/8] rust: pci: add sriov_get_totalvfs() helper

[Zhi Wang]

On Wed, 08 Jul 2026 23:13:08 +0900
"Alexandre Courbot" <acourbot@nvidia.com> wrote:

> On Wed Jul 8, 2026 at 11:03 PM JST, Alexandre Courbot wrote:
> > On Wed Jul 1, 2026 at 3:26 PM JST, Zhi Wang wrote:
> >> Expose pci_sriov_get_totalvfs() to Rust PCI drivers so they can
> >> query how many SR-IOV VFs a device supports.
> >>
> >> Cc: Alexandre Courbot <acourbot@nvidia.com>
> >> Cc: Bjorn Helgaas <bhelgaas@google.com>
> >> Cc: David Laight <david.laight.linux@gmail.com>
> >> Cc: Gary Guo <gary@garyguo.net>
> >> Cc: linux-pci@vger.kernel.org
> >> Link:
> >> https://lore.kernel.org/all/DJHPRE4TGGT8.BUTMYOF5YE05@nvidia.com/
> >> Signed-off-by: Zhi Wang <zhiw@nvidia.com> ---
> >>  rust/kernel/pci.rs | 11 +++++++++++
> >>  1 file changed, 11 insertions(+)
> >>
> >> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> >> index 5071cae6543f..21c51981c02e 100644
> >> --- a/rust/kernel/pci.rs
> >> +++ b/rust/kernel/pci.rs
> >> @@ -450,6 +450,17 @@ pub fn pci_class(&self) -> Class {
> >>          // SAFETY: `self.as_raw` is a valid pointer to a `struct
> >> pci_dev`. Class::from_raw(unsafe { (*self.as_raw()).class })
> >>      }
> >> +
> >> +    /// Returns the total number of VFs, or 0 if SR-IOV is not
> >> available.
> >> +    #[inline]
> >> +    pub fn sriov_get_totalvfs(&self) -> u16 {
> >> +        // SAFETY: `self.as_raw()` is a valid pointer to a
> >> `struct pci_dev`.
> >> +        let total_vfs = unsafe {
> >> bindings::pci_sriov_get_totalvfs(self.as_raw()) }; +
> >> +        // CAST: The C helper returns `unsigned int`, but the
> >> value originates
> >> +        // from TotalVFs/driver_max_VFs, so this cast cannot
> >> truncate.
> >
> > nit: "from TotalVFs/driver_max_VFs (which are defined as `u16`),
> > ..."
> >
> > With that,
> >
> > Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
> 
> ... with an additional item for thought: in a previous revision [1], I
> had raised the question of making the return type
> `Option<NonZero<u16>>`, as I think it better encodes "0 if SR-IOV is
> not available" - callers are then forced to consider the dichotomy of
> the result, and not interpret a particular value as having a special
> meaning.
> 
> OTOH, for all practical purposes 0 VFs also seems to be strictly
> equivalent to "SR-IOV is not available", so please take this as a
> nit to consider, not a blocker.
> 
> [1]
> https://lore.kernel.org/rust-for-linux/DETDILPA1GFY.27WND0TEC5352@nvidia.com/

Nice advice. I will address it in v4. :)

Re: [PATCH v3 2/8] rust: pci: add sriov_get_totalvfs() helper

[Zhi Wang]

On Wed, 08 Jul 2026 23:41:20 +0900
"Alexandre Courbot" <acourbot@nvidia.com> wrote:

> On Wed Jul 8, 2026 at 11:03 PM JST, Alexandre Courbot wrote:
> > On Wed Jul 1, 2026 at 3:26 PM JST, Zhi Wang wrote:  
> >> Expose pci_sriov_get_totalvfs() to Rust PCI drivers so they can
> >> query how many SR-IOV VFs a device supports.
> >>
> >> Cc: Alexandre Courbot <acourbot@nvidia.com>
> >> Cc: Bjorn Helgaas <bhelgaas@google.com>
> >> Cc: David Laight <david.laight.linux@gmail.com>
> >> Cc: Gary Guo <gary@garyguo.net>
> >> Cc: linux-pci@vger.kernel.org
> >> Link:
> >> https://lore.kernel.org/all/DJHPRE4TGGT8.BUTMYOF5YE05@nvidia.com/
> >> Signed-off-by: Zhi Wang <zhiw@nvidia.com> ---
> >>  rust/kernel/pci.rs | 11 +++++++++++
> >>  1 file changed, 11 insertions(+)
> >>
> >> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> >> index 5071cae6543f..21c51981c02e 100644
> >> --- a/rust/kernel/pci.rs
> >> +++ b/rust/kernel/pci.rs
> >> @@ -450,6 +450,17 @@ pub fn pci_class(&self) -> Class {
> >>          // SAFETY: `self.as_raw` is a valid pointer to a `struct
> >> pci_dev`. Class::from_raw(unsafe { (*self.as_raw()).class })
> >>      }
> >> +
> >> +    /// Returns the total number of VFs, or 0 if SR-IOV is not
> >> available.
> >> +    #[inline]
> >> +    pub fn sriov_get_totalvfs(&self) -> u16 {
> >> +        // SAFETY: `self.as_raw()` is a valid pointer to a
> >> `struct pci_dev`.
> >> +        let total_vfs = unsafe {
> >> bindings::pci_sriov_get_totalvfs(self.as_raw()) }; +
> >> +        // CAST: The C helper returns `unsigned int`, but the
> >> value originates
> >> +        // from TotalVFs/driver_max_VFs, so this cast cannot
> >> truncate.  
> >
> > nit: "from TotalVFs/driver_max_VFs (which are defined as `u16`),
> > ..."
> >
> > With that,
> >
> > Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>  
> 
> Sorry, need to take my tag back. :( Build is failing if
> `CONFIG_PCI_IOV` is not set:
> 
>     error[E0425]: cannot find function `pci_sriov_get_totalvfs` in
> crate `bindings` --> ../rust/kernel/pci.rs:458:44  
>         |
>     458 |         let total_vfs = unsafe {
> bindings::pci_sriov_get_totalvfs(self.as_raw()) }; |
>                           ^^^^^^^^^^^^^^^^^^^^^^ not found in
> `bindings`
> 
> Looks like you need to add a helper in `rust/helpers/pci.c` as the
> inline C function used when `CONFIG_PCI_IOV` is not set can not be
> invoked by Rust.

Add it in v4.