[PATCH v2 15/16] powerpc/powernv/sriov: Make single PE mode a per-BAR setting

[Michael Ellerman]

Nathan Chancellor <natechancellor at gmail.com> writes:
> On Wed, Jul 22, 2020 at 04:57:14PM +1000, Oliver O'Halloran wrote:
>> Using single PE BARs to map an SR-IOV BAR is really a choice about what
>> strategy to use when mapping a BAR. It doesn't make much sense for this to
>> be a global setting since a device might have one large BAR which needs to
>> be mapped with single PE windows and another smaller BAR that can be mapped
>> with a regular segmented window. Make the segmented vs single decision a
>> per-BAR setting and clean up the logic that decides which mode to use.
>> 
>> Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
>> ---
>> v2: Dropped unused total_vfs variables in pnv_pci_ioda_fixup_iov_resources()
>>     Dropped bar_no from pnv_pci_iov_resource_alignment()
>>     Minor re-wording of comments.
>> ---
>>  arch/powerpc/platforms/powernv/pci-sriov.c | 131 ++++++++++-----------
>>  arch/powerpc/platforms/powernv/pci.h       |  11 +-
>>  2 files changed, 73 insertions(+), 69 deletions(-)
>> 
>> diff --git a/arch/powerpc/platforms/powernv/pci-sriov.c b/arch/powerpc/platforms/powernv/pci-sriov.c
>> index ce8ad6851d73..76215d01405b 100644
>> --- a/arch/powerpc/platforms/powernv/pci-sriov.c
>> +++ b/arch/powerpc/platforms/powernv/pci-sriov.c
>> @@ -260,42 +256,40 @@ void pnv_pci_ioda_fixup_iov(struct pci_dev *pdev)
>>  resource_size_t pnv_pci_iov_resource_alignment(struct pci_dev *pdev,
>>  						      int resno)
>>  {
>> -	struct pnv_phb *phb = pci_bus_to_pnvhb(pdev->bus);
>>  	struct pnv_iov_data *iov = pnv_iov_get(pdev);
>>  	resource_size_t align;
>>  
>> +	/*
>> +	 * iov can be null if we have an SR-IOV device with IOV BAR that can't
>> +	 * be placed in the m64 space (i.e. The BAR is 32bit or non-prefetch).
>> +	 * In that case we don't allow VFs to be enabled since one of their
>> +	 * BARs would not be placed in the correct PE.
>> +	 */
>> +	if (!iov)
>> +		return align;
>> +	if (!iov->vfs_expanded)
>> +		return align;
>> +
>> +	align = pci_iov_resource_size(pdev, resno);

That's, oof.

> I am not sure if it has been reported yet but clang points out that
> align is initialized after its use:
>
> arch/powerpc/platforms/powernv/pci-sriov.c:267:10: warning: variable 'align' is uninitialized when used here [-Wuninitialized]
>                 return align;
>                        ^~~~~
> arch/powerpc/platforms/powernv/pci-sriov.c:258:23: note: initialize the variable 'align' to silence this warning
>         resource_size_t align;
>                              ^
>                               = 0
> 1 warning generated.

But I can't get gcc to warn about it?

It produces some code, so it's not like the whole function has been
elided or something. I'm confused.

cheers