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Date: Fri, 6 Nov 2020 11:41:21 -0800
From: David Awogbemila <awogbemila@...gle.com>
To: Saeed Mahameed <saeed@...nel.org>
Cc: netdev@...r.kernel.org, Catherine Sullivan <csully@...gle.com>,
Yangchun Fu <yangchun@...gle.com>
Subject: Re: [PATCH 1/4] gve: Add support for raw addressing device option
On Tue, Nov 3, 2020 at 2:43 PM Saeed Mahameed <saeed@...nel.org> wrote:
>
> On Tue, 2020-11-03 at 09:46 -0800, David Awogbemila wrote:
> > From: Catherine Sullivan <csully@...gle.com>
> >
> > Add support to describe device for parsing device options. As
> > the first device option, add raw addressing.
> >
> > "Raw Addressing" mode (as opposed to the current "qpl" mode) is an
> > operational mode which allows the driver avoid bounce buffer copies
> > which it currently performs using pre-allocated qpls
> > (queue_page_lists)
> > when sending and receiving packets.
> > For egress packets, the provided skb data addresses will be
> > dma_map'ed and
> > passed to the device, allowing the NIC can perform DMA directly - the
> > driver will not have to copy the buffer content into pre-allocated
> > buffers/qpls (as in qpl mode).
> > For ingress packets, copies are also eliminated as buffers are handed
> > to
> > the networking stack and then recycled or re-allocated as
> > necessary, avoiding the use of skb_copy_to_linear_data().
> >
> > This patch only introduces the option to the driver.
> > Subsequent patches will add the ingress and egress functionality.
> >
> > Reviewed-by: Yangchun Fu <yangchun@...gle.com>
> > Signed-off-by: Catherine Sullivan <csully@...gle.com>
> > Signed-off-by: David Awogbemila <awogbemila@...gle.com>
> > ---
> > drivers/net/ethernet/google/gve/gve.h | 1 +
> > drivers/net/ethernet/google/gve/gve_adminq.c | 52
> > ++++++++++++++++++++
> > drivers/net/ethernet/google/gve/gve_adminq.h | 15 ++++--
> > drivers/net/ethernet/google/gve/gve_main.c | 9 ++++
> > 4 files changed, 73 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/google/gve/gve.h
> > b/drivers/net/ethernet/google/gve/gve.h
> > index f5c80229ea96..80cdae06ee39 100644
> > --- a/drivers/net/ethernet/google/gve/gve.h
> > +++ b/drivers/net/ethernet/google/gve/gve.h
> > @@ -199,6 +199,7 @@ struct gve_priv {
> > u64 num_registered_pages; /* num pages registered with NIC */
> > u32 rx_copybreak; /* copy packets smaller than this */
> > u16 default_num_queues; /* default num queues to set up */
> > + bool raw_addressing; /* true if this dev supports raw
> > addressing */
> >
> > struct gve_queue_config tx_cfg;
> > struct gve_queue_config rx_cfg;
> > diff --git a/drivers/net/ethernet/google/gve/gve_adminq.c
> > b/drivers/net/ethernet/google/gve/gve_adminq.c
> > index 24ae6a28a806..0b7a2653fe33 100644
> > --- a/drivers/net/ethernet/google/gve/gve_adminq.c
> > +++ b/drivers/net/ethernet/google/gve/gve_adminq.c
> > @@ -460,11 +460,14 @@ int gve_adminq_destroy_rx_queues(struct
> > gve_priv *priv, u32 num_queues)
> > int gve_adminq_describe_device(struct gve_priv *priv)
> > {
> > struct gve_device_descriptor *descriptor;
> > + struct gve_device_option *dev_opt;
> > union gve_adminq_command cmd;
> > dma_addr_t descriptor_bus;
> > + u16 num_options;
> > int err = 0;
> > u8 *mac;
> > u16 mtu;
> > + int i;
> >
> > memset(&cmd, 0, sizeof(cmd));
> > descriptor = dma_alloc_coherent(&priv->pdev->dev, PAGE_SIZE,
> > @@ -518,6 +521,55 @@ int gve_adminq_describe_device(struct gve_priv
> > *priv)
> > priv->rx_desc_cnt = priv->rx_pages_per_qpl;
> > }
> > priv->default_num_queues = be16_to_cpu(descriptor-
> > >default_num_queues);
> > + dev_opt = (void *)(descriptor + 1);
> > +
> > + num_options = be16_to_cpu(descriptor->num_device_options);
> > + for (i = 0; i < num_options; i++) {
> > + u16 option_length = be16_to_cpu(dev_opt-
> > >option_length);
> > + u16 option_id = be16_to_cpu(dev_opt->option_id);
> > + void *option_end;
> > +
> > + option_end = (void *)dev_opt + sizeof(*dev_opt) +
> > option_length;
> > + if (option_end > (void *)descriptor +
> > be16_to_cpu(descriptor->total_length)) {
> > + dev_err(&priv->dev->dev,
> > + "options exceed device_descriptor's
> > total length.\n");
> > + err = -EINVAL;
> > + goto free_device_descriptor;
> > + }
> > +
> > + switch (option_id) {
> > + case GVE_DEV_OPT_ID_RAW_ADDRESSING:
> > + /* If the length or feature mask doesn't match,
> > + * continue without enabling the feature.
> > + */
> > + if (option_length !=
> > GVE_DEV_OPT_LEN_RAW_ADDRESSING ||
> > + dev_opt->feat_mask !=
> > + cpu_to_be32(GVE_DEV_OPT_FEAT_MASK_RAW_ADDRE
> > SSING)) {
> > + dev_warn(&priv->pdev->dev,
> > + "Raw addressing option
> > error:\n"
> > + " Expected: length=%d,
> > feature_mask=%x.\n"
> > + " Actual: length=%d,
> > feature_mask=%x.\n",
> > + GVE_DEV_OPT_LEN_RAW_ADDRESSING
> > ,
> > + cpu_to_be32(GVE_DEV_OPT_FEAT_M
> > ASK_RAW_ADDRESSING),
> > + option_length, dev_opt-
> > >feat_mask);
> > + priv->raw_addressing = false;
> > + } else {
> > + dev_info(&priv->pdev->dev,
> > + "Raw addressing device option
> > enabled.\n");
> > + priv->raw_addressing = true;
> > + }
> > + break;
> > + default:
> > + /* If we don't recognize the option just
> > continue
> > + * without doing anything.
> > + */
> > + dev_dbg(&priv->pdev->dev,
> > + "Unrecognized device option 0x%hx not
> > enabled.\n",
> > + option_id);
> > + break;
> > + }
> > + dev_opt = (void *)dev_opt + sizeof(*dev_opt) +
> > option_length;
>
> This was already calculated above, "option_end"
>
>
> Suggestion: you can make an iterator macro to return the next opt
>
> next_opt = GET_NEXT_OPT(descriptor, curr_opt);
>
> you can make it check boundaries and return null on last iteration or
> when total length is exceeded, and just use it in a more readable
> iterator loop.
>
Thanks for the suggestion. I will adopt a macro but it'll only return
NULL if the options exceed the boundary - that way we can distinguish
between an error (boundary exceeded) and the last option.
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