On Wed, Sep 17, 2014 at 10:50 AM, Zhang, Helin <helin.zhang at intel.com> wrote:
> For the ?extended tag?, it was defined in PCIe spec, but actually not > all BIOS implements it. Enabling it in BIOS or at runtime are two choices > of doing the same thing. I don?t think it can be configured per PCI device > in BIOS, so we don?t need to do that per PCI device in DPDK. Right? > Actually we don?t want to touch PCIe settings in DPDK code, that?s why we > want to let BIOS config as it is by default. If no better choice, we can do > it in DPDK by changing configurations. > - Ok, then if we can make a runtime decision (at dpdk level), there is no need for bios configuration and there is no need for a build option. Why don't we get rid of this option ? As far as the per-device runtime configuration is concerned, I want to make sure this pci configuration will not break other "igb_uio" pci devices. If Intel can tell for sure this won't break other devices, then fine, we can go and enable this for all "igb_uio" pci devices. - By the way, there is also the CONFIG_MAX_READ_REQUEST_SIZE option that seems to be disabled (or at least its value 0 seems to tell so). What is its purpose ? > > For ?CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n? by default, we want to > support 32 bytes rx descriptors by default. Two reasons: > > One is 32 bytes rx descriptors can provide more powerful features, and > more offload features. > > The other is Linux PF host use 32 bytes rx descriptor by default which > might not able to be changed, to support Linux PF host, it would be better > to use 32 bytes rx descriptors in DPDK VF by default. > Ok, good to know. Thanks. -- David Marchand
