Hi Anatoly,
Sorry for the late response.
> -----Original Message-----
> From: Burakov, Anatoly <anatoly.bura...@intel.com>
> Sent: Friday, November 9, 2018 8:15 PM
> To: Tone Zhang (Arm Technology China) <tone.zh...@arm.com>;
> dev@dpdk.org
> Cc: Gavin Hu (Arm Technology China) <gavin...@arm.com>; Honnappa
> Nagarahalli <honnappa.nagaraha...@arm.com>; Steve Capper
> <steve.cap...@arm.com>; nd <n...@arm.com>
> Subject: Re: [PATCH v2] pci_vfio: Support 64KB kernel page_size with vfio-pci
> driver
>
> On 09-Nov-18 5:57 AM, tone.zhang wrote:
> > With a larger PAGE_SIZE it is possible for the MSI table to very close
> > to the end of the BAR s.t. when we align the start and end of the MSI
> > table to the PAGE_SIZE, the end offset of the MSI table is out of the
> > PCI BAR boundary.
> >
> > This patch addresses the issue by comparing both the start and the end
> > offset of the MSI table with the BAR size, and skip the mapping if it
> > is out of Bar scope.
> >
> > The patch fixes the debug log as below:
> > EAL: Skipping BAR0
> >
> > Signed-off-by: tone.zhang <tone.zh...@arm.com>
> > Reviewed-by: Gavin Hu <gavin...@arm.com>
> > Reviewed-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
> > Reviewed-by: Steve Capper <steve.cap...@arm.com>
> > Reviewed-by: Burakov Anatoly <anatoly.bura...@intel.com>
>
> In the future, please don't include my Reviewed tag unless i actually sent
> one :)
Thanks a lot! Will keep in mind. 😊
>
> > ---
> > drivers/bus/pci/linux/pci_vfio.c | 36 +++++++++++++++++++++++++++++++---
> --
> > 1 file changed, 31 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/bus/pci/linux/pci_vfio.c
> > b/drivers/bus/pci/linux/pci_vfio.c
> > index 305cc06..9a0affe 100644
> > --- a/drivers/bus/pci/linux/pci_vfio.c
> > +++ b/drivers/bus/pci/linux/pci_vfio.c
> > @@ -445,9 +445,11 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct
> mapped_pci_resource *vfio_res,
> > struct pci_msix_table *msix_table = &vfio_res->msix_table;
> > struct pci_map *bar = &vfio_res->maps[bar_index];
> >
> > - if (bar->size == 0)
> > + if (bar->size == 0) {
> > /* Skip this BAR */
> > + RTE_LOG(INFO, EAL, "Skipping BAR%d\n", bar_index);
> > return 0;
> > + }
> >
> > if (msix_table->bar_index == bar_index) {
> > /*
> > @@ -456,8 +458,22 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct
> mapped_pci_resource *vfio_res,
> > */
> > uint32_t table_start = msix_table->offset;
> > uint32_t table_end = table_start + msix_table->size;
> > - table_end = (table_end + ~PAGE_MASK) & PAGE_MASK;
> > - table_start &= PAGE_MASK;
> > + table_end = RTE_ALIGN(table_end, PAGE_SIZE);
> > + table_start = RTE_ALIGN(table_start, PAGE_SIZE);
> > + /* after rounding to PAGE_SIZE, it is over the bar->size,
> > + * fall back to the MSI-X table offset in the bar and
> > + * align with PAGE_SIZE.
> > + */
>
> Minor nitpick - wording of comment could be better, for example:
>
> if page-aligned start of MSI-X table is beyond BAR size, shrink the mapping
> size
> to MSI-X table start address.
>
> Also, probably needs newline before comment.
>
Will update the code in next version. Thanks!
> > + if (table_start >= bar->size) {
> > + table_start = RTE_ALIGN_FLOOR(msix_table->offset,
> > + PAGE_SIZE);
> > + /* after aligning with PAGE_SIZE, if it is less than
> > + * the MSI-X table offset, continue falling back to
> > + * the actual MSI-X table offset in the bar.
> > + */
>
> Same here, wording could probably be improved. Suggested rewording:
>
> If MSI-X table address, floor-aligned by page size, is lower than actual MSI-X
> table offset, fall back to using MSI-X table offset as table start.
>
> Now that i think of it, this could really be expressed like this:
>
> uint32_t aligned = RTE_ALIGN_FLOOR(msix_table->offset, PAGE_SIZE);
> table_start = RTE_MAX(aligned, msix_table_offset);
>
> I believe this would be much clearer.
>
Will update the patch.
> > + if (table_start < msix_table->offset)
> > + table_start = msix_table->offset;
> > + }
> >
> > if (table_start == 0 && table_end >= bar->size) {
> > /* Cannot map this BAR */
> > @@ -469,8 +485,18 @@ pci_vfio_mmap_bar(int vfio_dev_fd, struct
> > mapped_pci_resource *vfio_res,
> >
> > memreg[0].offset = bar->offset;
> > memreg[0].size = table_start;
> > - memreg[1].offset = bar->offset + table_end;
> > - memreg[1].size = bar->size - table_end;
> > + if (bar->size < table_end) {
> > + /*
> > + * after rounding to PAGE_SIZE we don't have any space
> > + * left after the MSI table, so don't try and map it.
> > + */
>
> Suggested rewording:
>
> If MSI-X table end is beyond BAR end, don't attempt to perform second mapping.
>
Thanks a lot. Will update.
> > + memreg[1].offset = 0;
> > + memreg[1].size = 0;
> > + }
> > + else {
> > + memreg[1].offset = bar->offset + table_end;
> > + memreg[1].size = bar->size - table_end;
> > + }
> >
> > RTE_LOG(DEBUG, EAL,
> > "Trying to map BAR%d that contains the MSI-X "
> >
>
> However, the patch can go in as is if needed, so
>
> Reviewed-by: Anatoly Burakov <anatoly.bura...@intel.com>
>
Thanks! 😉
> --
> Thanks,
> Anatoly
Br,
Tone
