Re: [PATCH] PCI: endpoint: pci-epf-test: Make use of cached 'epc_features' in pci_epf_test_core_init()

Niklas Cassel
2024-04-17T17:55:01Z

On Wed, Apr 17, 2024 at 07:49:45PM +0200, Niklas Cassel wrote:
> On Wed, Apr 17, 2024 at 10:47:25PM +0530, Manivannan Sadhasivam wrote:
> > Instead of getting the epc_features from pci_epc_get_features() API, use
> > the cached pci_epf_test::epc_features value to avoid the NULL check. Since
> > the NULL check is already performed in pci_epf_test_bind(), having one more
> > check in pci_epf_test_core_init() is redundant and it is not possible to
> > hit the NULL pointer dereference. This also leads to the following smatch
> > warning:
> >
> > drivers/pci/endpoint/functions/pci-epf-test.c:784 pci_epf_test_core_init()
> > error: we previously assumed 'epc_features' could be null (see line 747)
> >
> > Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > Closes: https://lore.kernel.org/linux-pci/024b5826-7180-4076-ae08-57d2584cca3f@moroto.mountain/
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
>
> I think you forgot:
> Fixes: a01e7214bef9 ("PCI: endpoint: Remove "core_init_notifier" flag")
>
>
> > ---
> > drivers/pci/endpoint/functions/pci-epf-test.c | 9 ++++-----
> > 1 file changed, 4 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> > index 977fb79c1567..0d28f413cb07 100644
> > --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> > +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> > @@ -743,11 +743,10 @@ static int pci_epf_test_core_init(struct pci_epf *epf)
> > bool msi_capable = true;
> > int ret;
> >
> > - epc_features = pci_epc_get_features(epc, epf->func_no, epf->vfunc_no);
> > - if (epc_features) {
> > - msix_capable = epc_features->msix_capable;
> > - msi_capable = epc_features->msi_capable;
> > - }
> > + epc_features = epf_test->epc_features;
>
> How about:
>
> index 977fb79c1567..4d6105c07ac0 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -735,7 +735,7 @@ static int pci_epf_test_core_init(struct pci_epf *epf)
> {
> struct pci_epf_test *epf_test = epf_get_drvdata(epf);
> struct pci_epf_header *header = epf->header;
> - const struct pci_epc_features *epc_features;
> + const struct pci_epc_features *epc_features = epf_test->epc_features;
> struct pci_epc *epc = epf->epc;
> struct device *dev = &epf->dev;
> bool linkup_notifier = false;
> @@ -743,12 +743,6 @@ static int pci_epf_test_core_init(struct pci_epf *epf)
> bool msi_capable = true;
> int ret;
>
> - epc_features = pci_epc_get_features(epc, epf->func_no, epf->vfunc_no);
> - if (epc_features) {
> - msix_capable = epc_features->msix_capable;
> - msi_capable = epc_features->msi_capable;
> - }
> -
> if (epf->vfunc_no <= 1) {
> ret = pci_epc_write_header(epc, epf->func_no, epf->vfunc_no, header);
> if (ret) {
> @@ -761,6 +755,7 @@ static int pci_epf_test_core_init(struct pci_epf *epf)
> if (ret)
> return ret;
>
> + msi_capable = epc_features->msi_capable;
> if (msi_capable) {
> ret = pci_epc_set_msi(epc, epf->func_no, epf->vfunc_no,
> epf->msi_interrupts);
> @@ -770,6 +765,7 @@ static int pci_epf_test_core_init(struct pci_epf *epf)
> }
> }
>
> + msix_capable = epc_features->msix_capable;
> if (msix_capable) {
> ret = pci_epc_set_msix(epc, epf->func_no, epf->vfunc_no,
> epf->msix_interrupts,
> @@ -814,11 +810,9 @@ static int pci_epf_test_alloc_space(struct pci_epf *epf)
> void *base;
> enum pci_barno test_reg_bar = epf_test->test_reg_bar;
> enum pci_barno bar;
> - const struct pci_epc_features *epc_features;
> + const struct pci_epc_features *epc_features = epf_test->epc_features;
> size_t test_reg_size;
>
> - epc_features = epf_test->epc_features;
> -
> test_reg_bar_size = ALIGN(sizeof(struct pci_epf_test_reg), 128);
>
> msix_capable = epc_features->msix_capable;
>
>
> Instead?
>
> That way, we assign msi_capable/msix_capable just before the if-statement
> where it is used. (Which matches how we already assign msix_capable just
> before the if-statement in pci_epf_test_alloc_space().)

...or just kill the local variables:
bool msi_capable/msix_capable in pci_epf_test_core_init(), and
bool msix_capable pci_epf_test_alloc_space()
and just do:

if (epc_features->msix_capable) / if (epc_features->msi_capable)

directly?

Kind regards,
Niklas