Hi Chenbo,
Thanks your comments.
> -----Original Message-----
> From: Xia, Chenbo <chenbo....@intel.com>
> Sent: Wednesday, July 8, 2020 9:58 PM
> To: Zhang, AlvinX <alvinx.zh...@intel.com>; dev@dpdk.org
> Cc: Xing, Beilei <beilei.x...@intel.com>; Guo, Jia <jia....@intel.com>; David
> Marchand <david.march...@redhat.com>; Tal Shnaiderman
> <tal...@mellanox.com>; Burakov, Anatoly <anatoly.bura...@intel.com>;
> tho...@monjalon.net
> Subject: RE: [dpdk-dev] [PATCH] bus/pci: fix mmap PCI resource
>
> Hi Alvin,
>
> CC the maintainers. Comments below.
>
> > -----Original Message-----
> > From: dev <dev-boun...@dpdk.org> On Behalf Of alvinx.zh...@intel.com
> > Sent: Wednesday, July 8, 2020 5:25 PM
> > To: dev@dpdk.org
> > Cc: Xing, Beilei <beilei.x...@intel.com>; Guo, Jia <jia....@intel.com>
> > Subject: [dpdk-dev] [PATCH] bus/pci: fix mmap PCI resource
> >
> > From: Alvin Zhang <alvinx.zh...@intel.com>
> >
> > When mapping a PCI BAR containing an MSI-X table, some devices do not
> > need to actually map this BAR or only need to map part of them, which
> > may cause the mapping to fail. Now some checks are added and a
> > non-NULL initial value is set to the variable to avoid this situation.
> >
> > Fixes: 2fd3567e5425 ("pci: use OS generic memory mapping functions")
> > Cc: tal...@mellanox.com
> >
> > Signed-off-by: Alvin Zhang <alvinx.zh...@intel.com>
> > ---
> > drivers/bus/pci/linux/pci_vfio.c | 12 +++++++++++-
> > 1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/bus/pci/linux/pci_vfio.c
> > b/drivers/bus/pci/linux/pci_vfio.c
> > index fdeb9a8..9143bfc 100644
> > --- a/drivers/bus/pci/linux/pci_vfio.c
> > +++ b/drivers/bus/pci/linux/pci_vfio.c
> > @@ -547,6 +547,14 @@
> > bar_index,
> > memreg[0].offset, memreg[0].size,
> > memreg[1].offset, memreg[1].size);
> > +
> > + if (memreg[0].size == 0 && memreg[1].size == 0) {
> > + /* No need to map this BAR */
> > + RTE_LOG(DEBUG, EAL, "Skipping BAR%d\n", bar_index);
> > + bar->size = 0;
> > + bar->addr = 0;
> > + return 0;
> > + }
>
> I'm not sure if this corner case will happen. If you confirmed it, Just
> ignore this.
In theory, it is entirely possible if the misx-table size is equal to the bar
size.
>
> > } else {
> > memreg[0].offset = bar->offset;
> > memreg[0].size = bar->size;
> > @@ -556,7 +564,9 @@
> > bar_addr = mmap(bar->addr, bar->size, 0, MAP_PRIVATE |
> > MAP_ANONYMOUS | additional_flags, -1, 0);
> > if (bar_addr != MAP_FAILED) {
> > - void *map_addr = NULL;
> > + /* Set non NULL initial value for in case of no PCI mapping */
> > + void *map_addr = bar_addr;
> > +
>
> I see the issue that this patch wants to fix is based on an old kernel.
> In older vfio-pci kernel module, MSI related reg cannot be mmaped in userspace
> while in newer kernel it can be. That's why sometimes it cannot be reproduced
> (https://bugs.dpdk.org/show_bug.cgi?id=503)
>
> So under the condition of old kernel, there could be an example that Memreg 0
> has size 0 but Memreg 1 has non-zero size, which leads to Memreg 1 cannot be
> mmaped.
Yes, it is.
>
> So I'm fine with this part of code change. As this issue is blocking test, we
> should
> do fast confirm and review.
>
> Thanks,
> Chenbo
>
> > if (memreg[0].size) {
> > /* actual map of first part */
> > map_addr = pci_map_resource(bar_addr, vfio_dev_fd,
> > --
> > 1.8.3.1
