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[79.178.123.8]) by smtp.gmail.com with ESMTPSA id h7sm2543166wmf.43.2020.08.05.05.06.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Aug 2020 05:06:29 -0700 (PDT) Date: Wed, 5 Aug 2020 08:06:27 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v2 22/24] vdpa_sim: fix endian-ness of config space Message-ID: <20200805080434-mutt-send-email-mst@kernel.org> References: <20200803205814.540410-1-mst@redhat.com> <20200803205814.540410-23-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 05, 2020 at 02:21:07PM +0800, Jason Wang wrote: > > On 2020/8/4 上午5:00, Michael S. Tsirkin wrote: > > VDPA sim accesses config space as native endian - this is > > wrong since it's a modern device and actually uses LE. > > > > It only supports modern guests so we could punt and > > just force LE, but let's use the full virtio APIs since people > > tend to copy/paste code, and this is not data path anyway. > > > > Signed-off-by: Michael S. Tsirkin > > --- > > drivers/vdpa/vdpa_sim/vdpa_sim.c | 31 ++++++++++++++++++++++++++----- > > 1 file changed, 26 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c > > index a9bc5e0fb353..fa05e065ff69 100644 > > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c > > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c > > @@ -24,6 +24,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > @@ -72,6 +73,23 @@ struct vdpasim { > > u64 features; > > }; > > +/* TODO: cross-endian support */ > > +static inline bool vdpasim_is_little_endian(struct vdpasim *vdpasim) > > +{ > > + return virtio_legacy_is_little_endian() || > > + (vdpasim->features & (1ULL << VIRTIO_F_VERSION_1)); > > +} > > + > > +static inline u16 vdpasim16_to_cpu(struct vdpasim *vdpasim, __virtio16 val) > > +{ > > + return __virtio16_to_cpu(vdpasim_is_little_endian(vdpasim), val); > > +} > > + > > +static inline __virtio16 cpu_to_vdpasim16(struct vdpasim *vdpasim, u16 val) > > +{ > > + return __cpu_to_virtio16(vdpasim_is_little_endian(vdpasim), val); > > +} > > + > > static struct vdpasim *vdpasim_dev; > > static struct vdpasim *vdpa_to_sim(struct vdpa_device *vdpa) > > @@ -306,7 +324,6 @@ static const struct vdpa_config_ops vdpasim_net_config_ops; > > static struct vdpasim *vdpasim_create(void) > > { > > - struct virtio_net_config *config; > > struct vdpasim *vdpasim; > > struct device *dev; > > int ret = -ENOMEM; > > @@ -331,10 +348,7 @@ static struct vdpasim *vdpasim_create(void) > > if (!vdpasim->buffer) > > goto err_iommu; > > - config = &vdpasim->config; > > - config->mtu = 1500; > > - config->status = VIRTIO_NET_S_LINK_UP; > > - eth_random_addr(config->mac); > > + eth_random_addr(vdpasim->config.mac); > > vringh_set_iotlb(&vdpasim->vqs[0].vring, vdpasim->iommu); > > vringh_set_iotlb(&vdpasim->vqs[1].vring, vdpasim->iommu); > > @@ -448,6 +462,7 @@ static u64 vdpasim_get_features(struct vdpa_device *vdpa) > > static int vdpasim_set_features(struct vdpa_device *vdpa, u64 features) > > { > > struct vdpasim *vdpasim = vdpa_to_sim(vdpa); > > + struct virtio_net_config *config = &vdpasim->config; > > /* DMA mapping must be done by driver */ > > if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM))) > > @@ -455,6 +470,12 @@ static int vdpasim_set_features(struct vdpa_device *vdpa, u64 features) > > vdpasim->features = features & vdpasim_features; > > + /* We only know whether guest is using the legacy interface here, so > > + * that's the earliest we can set config fields. > > + */ > > > We check whether or not ACCESS_PLATFORM is set before which is probably a > hint that only modern device is supported. So I wonder just force LE and > fail if VERSION_1 is not set is better? > > Thanks So how about I add a comment along the lines of /* * vdpasim ATM requires VIRTIO_F_ACCESS_PLATFORM, so we don't need to * support legacy guests. Keep transitional device code around for * the benefit of people who might copy-and-paste this into transitional * device code. */ > > > + > > + config->mtu = cpu_to_vdpasim16(vdpasim, 1500); > > + config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP); > > return 0; > > }