From: Jason Wang <jasowang@redhat.com> To: "Michael S. Tsirkin" <mst@redhat.com> Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, shahafs@mellanox.com Subject: Re: [PATCH V2 02/14] virtio-pci: switch to use devres for modern devices Date: Fri, 27 Nov 2020 10:54:14 +0800 [thread overview] Message-ID: <9638da54-394c-98f1-ad0e-12f3f0ddf17e@redhat.com> (raw) In-Reply-To: <20201126084708-mutt-send-email-mst@kernel.org> On 2020/11/26 下午9:57, Michael S. Tsirkin wrote: > On Thu, Nov 26, 2020 at 05:25:52PM +0800, Jason Wang wrote: >> This patch tries to convert the modern device to use devres to manage >> its resources (iomaps). Before this patch the IO address is mapped >> individually according to the capability. After this patch, we simply >> map the whole BAR. > I think the point of mapping capability was e.g. for devices with > huge BARs. We don't want to waste virtual memory for e.g. 32 bit guests. > > And in particular the spec says: > > The drivers SHOULD only map part of configuration structure large enough for device operation. The drivers > MUST handle an unexpectedly large length, but MAY check that length is large enough for device operation. Good point, so I will stick to devres but not use the shortcut like whole BAR mapping. > > I also wonder how would this interact with cases where device memory is > mapped for different reasons, such as for MSI table access, into userspace > as it has resources such as virtio mem, etc. I think it depends on the driver, e.g for virtio-pci and vDPA, the upper layer driver (virtio bus or vDPA bus) know nothing about transport specific thing. It should be ok. > E.g. don't e.g. intel CPUs disallow mapping the same address twice > with different attributes? Do you mean it doesn't allow one VA is mapped as UC but the other is not? I don't know. But anyhow my understanding is that virtio-pci/vp_vdpa tries to hide the details so we can not have two mappings here. Thanks >
WARNING: multiple messages have this Message-ID (diff)
From: Jason Wang <jasowang@redhat.com> To: "Michael S. Tsirkin" <mst@redhat.com> Cc: shahafs@mellanox.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH V2 02/14] virtio-pci: switch to use devres for modern devices Date: Fri, 27 Nov 2020 10:54:14 +0800 [thread overview] Message-ID: <9638da54-394c-98f1-ad0e-12f3f0ddf17e@redhat.com> (raw) In-Reply-To: <20201126084708-mutt-send-email-mst@kernel.org> On 2020/11/26 下午9:57, Michael S. Tsirkin wrote: > On Thu, Nov 26, 2020 at 05:25:52PM +0800, Jason Wang wrote: >> This patch tries to convert the modern device to use devres to manage >> its resources (iomaps). Before this patch the IO address is mapped >> individually according to the capability. After this patch, we simply >> map the whole BAR. > I think the point of mapping capability was e.g. for devices with > huge BARs. We don't want to waste virtual memory for e.g. 32 bit guests. > > And in particular the spec says: > > The drivers SHOULD only map part of configuration structure large enough for device operation. The drivers > MUST handle an unexpectedly large length, but MAY check that length is large enough for device operation. Good point, so I will stick to devres but not use the shortcut like whole BAR mapping. > > I also wonder how would this interact with cases where device memory is > mapped for different reasons, such as for MSI table access, into userspace > as it has resources such as virtio mem, etc. I think it depends on the driver, e.g for virtio-pci and vDPA, the upper layer driver (virtio bus or vDPA bus) know nothing about transport specific thing. It should be ok. > E.g. don't e.g. intel CPUs disallow mapping the same address twice > with different attributes? Do you mean it doesn't allow one VA is mapped as UC but the other is not? I don't know. But anyhow my understanding is that virtio-pci/vp_vdpa tries to hide the details so we can not have two mappings here. Thanks > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2020-11-27 2:54 UTC|newest] Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-11-26 9:25 [PATCH V2 00/14] vDPA driver for virtio-pci device Jason Wang 2020-11-26 9:25 ` Jason Wang 2020-11-26 9:25 ` [PATCH V2 01/14] virtio-pci: do not access iomem via virtio_pci_device directly Jason Wang 2020-11-26 9:25 ` Jason Wang 2020-11-26 13:46 ` Michael S. Tsirkin 2020-11-26 13:46 ` Michael S. Tsirkin 2020-11-27 2:50 ` Jason Wang 2020-11-27 2:50 ` Jason Wang 2020-11-26 9:25 ` [PATCH V2 02/14] virtio-pci: switch to use devres for modern devices Jason Wang 2020-11-26 9:25 ` Jason Wang 2020-11-26 13:57 ` Michael S. Tsirkin 2020-11-26 13:57 ` Michael S. Tsirkin 2020-11-27 2:54 ` Jason Wang [this message] 2020-11-27 2:54 ` Jason Wang 2020-11-26 9:25 ` [PATCH V2 03/14] virtio-pci: split out modern device Jason Wang 2020-11-26 9:25 ` Jason Wang 2020-11-26 9:25 ` [PATCH V2 04/14] virtio-pci: move the notification sanity check to vp_modern_probe() Jason Wang 2020-11-26 9:25 ` Jason Wang 2020-11-26 9:25 ` [PATCH V2 05/14] virtio-pci-modern: introduce vp_modern_set_queue_vector() Jason Wang 2020-11-26 9:25 ` Jason Wang 2020-11-26 9:25 ` [PATCH V2 06/14] virtio-pci-modern: introduce vp_modern_queue_address() Jason Wang 2020-11-26 9:25 ` Jason Wang 2020-11-26 9:25 ` [PATCH V2 07/14] virtio-pci-modern: introduce helper to set/get queue_enable Jason Wang 2020-11-26 9:25 ` Jason Wang 2020-11-26 9:25 ` [PATCH V2 08/14] virtio-pci-modern: introduce helper for setting/geting queue size Jason Wang 2020-11-26 9:25 ` Jason Wang 2020-11-26 9:25 ` [PATCH V2 09/14] virtio-pci-modern: introduce helper for getting queue nums Jason Wang 2020-11-26 9:25 ` Jason Wang 2020-11-26 9:26 ` [PATCH V2 10/14] virtio-pci-modern: introduce helper to get notification offset Jason Wang 2020-11-26 9:26 ` Jason Wang 2020-11-26 9:26 ` [PATCH V2 11/14] virtio-pci: introduce modern device module Jason Wang 2020-11-26 9:26 ` Jason Wang 2020-11-26 9:26 ` [PATCH V2 12/14] vdpa: set the virtqueue num during register Jason Wang 2020-11-26 9:26 ` Jason Wang 2020-11-26 9:26 ` [PATCH V2 13/14] virtio_vdpa: don't warn when fail to disable vq Jason Wang 2020-11-26 9:26 ` Jason Wang 2020-11-26 9:26 ` [PATCH V2 14/14] vdpa: introduce virtio pci driver Jason Wang 2020-11-26 9:26 ` Jason Wang
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