Messages in this thread Patch in this message | | | Subject | Re: [PATCH v4 1/3] PCI/IOV: Mark VFs as not implementing MSE bit | From | Matthew Rosato <> | Date | Thu, 3 Sep 2020 13:10:02 -0400 |
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On 9/3/20 12:41 PM, Bjorn Helgaas wrote: > On Wed, Sep 02, 2020 at 03:46:34PM -0400, Matthew Rosato wrote: >> Per the PCIe spec, VFs cannot implement the MSE bit >> AKA PCI_COMMAND_MEMORY, and it must be hard-wired to 0. >> Use a dev_flags bit to signify this requirement. > > This approach seems sensible to me, but > > - This is confusing because while the spec does not use "MSE" to > refer to the Command Register "Memory Space Enable" bit > (PCI_COMMAND_MEMORY), it *does* use "MSE" in the context of the > "VF MSE" bit, which is in the PF SR-IOV Capability. But of > course, you're not talking about that here. Maybe something like > this? > > For VFs, the Memory Space Enable bit in the Command Register is > hard-wired to 0. > > Add a dev_flags bit to signify devices where the Command > Register Memory Space Enable bit does not control the device's > response to MMIO accesses.
Will do. I'll change the usage of the MSE acronym in the other patches as well.
> > - "PCI_DEV_FLAGS_FORCE_COMMAND_MEM" says something about how you > plan to *use* this, but I'd rather use a term that describes the > hardware, e.g., "PCI_DEV_FLAGS_NO_COMMAND_MEMORY".
Sure, I will change.
> > - How do we decide whether to use dev_flags vs a bitfield like > dev->is_virtfn? The latter seems simpler unless there's a reason > to use dev_flags. If there's a reason, maybe we could add a > comment at pci_dev_flags for future reference. >
Something like:
/* * Device does not implement PCI_COMMAND_MEMORY - this is true for any * device marked is_virtfn, but is also true for any VF passed-through * a lower-level hypervisor where emulation of the Memory Space Enable * bit was not provided. */ PCI_DEV_FLAGS_NO_COMMAND_MEMORY = (__force pci_dev_flags_t) (1 << 12),
?
> - Wrap the commit log to fill a 75-char line. It's arbitrary, but > that's what I use for consistency.
Sure, will do. I'll roll up a new version once I have feedback from Alex on the vfio changes.
> >> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com> >> --- >> drivers/pci/iov.c | 1 + >> include/linux/pci.h | 2 ++ >> 2 files changed, 3 insertions(+) >> >> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c >> index b37e08c..2bec77c 100644 >> --- a/drivers/pci/iov.c >> +++ b/drivers/pci/iov.c >> @@ -180,6 +180,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id) >> virtfn->device = iov->vf_device; >> virtfn->is_virtfn = 1; >> virtfn->physfn = pci_dev_get(dev); >> + virtfn->dev_flags |= PCI_DEV_FLAGS_FORCE_COMMAND_MEM; >> >> if (id == 0) >> pci_read_vf_config_common(virtfn); >> diff --git a/include/linux/pci.h b/include/linux/pci.h >> index 8355306..9316cce 100644 >> --- a/include/linux/pci.h >> +++ b/include/linux/pci.h >> @@ -227,6 +227,8 @@ enum pci_dev_flags { >> PCI_DEV_FLAGS_NO_FLR_RESET = (__force pci_dev_flags_t) (1 << 10), >> /* Don't use Relaxed Ordering for TLPs directed at this device */ >> PCI_DEV_FLAGS_NO_RELAXED_ORDERING = (__force pci_dev_flags_t) (1 << 11), >> + /* Device does not implement PCI_COMMAND_MEMORY (e.g. a VF) */ >> + PCI_DEV_FLAGS_FORCE_COMMAND_MEM = (__force pci_dev_flags_t) (1 << 12), >> }; >> >> enum pci_irq_reroute_variant { >> -- >> 1.8.3.1 >>
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