netdev - Re: [net-next 1/4] gve: Add basic driver framework for Compute Engine Virtual NIC

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Date:   Fri, 28 Jun 2019 10:52:27 -0700
From:   Catherine Sullivan <csully@...gle.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     netdev@...r.kernel.org, Sagi Shahar <sagis@...gle.com>,
        Jon Olson <jonolson@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Luigi Rizzo <lrizzo@...gle.com>
Subject: Re: [net-next 1/4] gve: Add basic driver framework for Compute Engine
 Virtual NIC

On Wed, Jun 26, 2019 at 4:08 PM Jakub Kicinski
<jakub.kicinski@...ronome.com> wrote:
>
> On Wed, 26 Jun 2019 11:52:48 -0700, Catherine Sullivan wrote:
> > Add a driver framework for the Compute Engine Virtual NIC that will be
> > available in the future.
> >
> > At this point the only functionality is loading the driver.
> >
> > Signed-off-by: Catherine Sullivan <csully@...gle.com>
> > Signed-off-by: Sagi Shahar <sagis@...gle.com>
> > Signed-off-by: Jon Olson <jonolson@...gle.com>
> > Acked-by: Willem de Bruijn <willemb@...gle.com>
> > Reviewed-by: Luigi Rizzo <lrizzo@...gle.com>
> > ---
>
> > +if NET_VENDOR_GOOGLE
> > +
> > +config GVE
> > +     tristate "Google Virtual NIC (gVNIC) support"
> > +     depends on (PCI_MSI && X86)
>
> We usually prefer for drivers not to depend on the platform unless
> really necessary, but IDK how that applies to the curious new world
> of NICs nobody can buy :)

This is the only platform it will ever need to run on so we would really
prefer to not have to support others :)

>
> > +     help
> > +       This driver supports Google Virtual NIC (gVNIC)"
> > +
> > +       To compile this driver as a module, choose M here.
> > +       The module will be called gve.
> > +
> > +endif #NET_VENDOR_GOOGLE
>
> > +void gve_adminq_release(struct gve_priv *priv)
> > +{
> > +     int i;
> > +
> > +     /* Tell the device the adminq is leaving */
> > +     writel(0x0, &priv->reg_bar0->adminq_pfn);
> > +     for (i = 0; i < GVE_MAX_ADMINQ_RELEASE_CHECK; i++) {
> > +             if (!readl(&priv->reg_bar0->adminq_pfn)) {
> > +                     gve_clear_device_rings_ok(priv);
> > +                     gve_clear_device_resources_ok(priv);
> > +                     gve_clear_admin_queue_ok(priv);
> > +                     return;
> > +             }
> > +             msleep(GVE_ADMINQ_SLEEP_LEN);
> > +     }
> > +     /* If this is reached the device is unrecoverable and still holding
> > +      * memory. Anything other than a BUG risks memory corruption.
> > +      */
> > +     WARN(1, "Unrecoverable platform error!");
> > +     BUG();
>
> Please don't add BUG()s to the kernel.  You're probably better off
> spinning for ever in the loop above.  Also if there is an IOMMU in
> the way the device won't be able to mess with the memory.

Ack, it will be switched to a loop that won't end in v2.

>
> > +}
> > +
>
> > diff --git a/drivers/net/ethernet/google/gve/gve_size_assert.h b/drivers/net/ethernet/google/gve/gve_size_assert.h
> > new file mode 100644
> > index 000000000000..a58422d4f16e
> > --- /dev/null
> > +++ b/drivers/net/ethernet/google/gve/gve_size_assert.h
> > @@ -0,0 +1,15 @@
> > +/* SPDX-License-Identifier: (GPL-2.0 OR MIT)
> > + * Google virtual Ethernet (gve) driver
> > + *
> > + * Copyright (C) 2015-2019 Google, Inc.
> > + */
> > +
> > +#ifndef _GVE_ASSERT_H_
> > +#define _GVE_ASSERT_H_
> > +#define GVE_ASSERT_SIZE(tag, type, size) \
> > +     static void gve_assert_size_ ## type(void) __attribute__((used)); \
> > +     static inline void gve_assert_size_ ## type(void) \
> > +     { \
> > +             BUILD_BUG_ON(sizeof(tag type) != (size)); \
> > +     }
> > +#endif /* _GVE_ASSERT_H_ */
>
> Please use static_assert() directly in your struct size checks.

Thanks - that is much cleaner. Fixed in v2.