search for: descriptors

On 2017?09?10? 13:06, Michael S. Tsirkin wrote: > This is an update from v2 version. > Changes: > - update event suppression mechanism > - add wrap counter: DESC_WRAP flag in addition to > DESC_DRIVER flag used for validity so device does not have to > write out all used descriptors. Do we have benchmark result to show the advantage of DESC_DRIVER over e.g avail/used index? > - more options especially helpful for hardware implementations > - in-order processing option due to popular demand > - list of TODO items to consider as a follow-up, only two are > open...

...separate options for indirect and direct s/g - lots of new features --- Performance analysis of this is in my kvm forum 2016 presentation. The idea is to have a r/w descriptor in a ring structure, replacing the used and available ring, index and descriptor buffer. * Descriptor ring: Guest adds descriptors with unique index values and DESC_HW set in flags. Host overwrites used descriptors with correct len, index, and DESC_HW clear. Flags are always set/cleared last. #define DESC_HW 0x0080 struct desc { __le64 addr; __le32 len; __le16 index; __le16 flags; }; When DE...

...separate options for indirect and direct s/g - lots of new features --- Performance analysis of this is in my kvm forum 2016 presentation. The idea is to have a r/w descriptor in a ring structure, replacing the used and available ring, index and descriptor buffer. * Descriptor ring: Guest adds descriptors with unique index values and DESC_HW set in flags. Host overwrites used descriptors with correct len, index, and DESC_HW clear. Flags are always set/cleared last. #define DESC_HW 0x0080 struct desc { __le64 addr; __le32 len; __le16 index; __le16 flags; }; When DE...

Greetings all, Anyone done any work on these products? I have several (a couple of different models) that are rebranded Ultra in the US. Using explore with usbhid returns some significant quantities of data and I've done some captures with usbsnoop. I've also asked Ultra to get me the HID definition that was used for them, in the hopes I don't have to usbsniff all the setting

...tio-dev at lists.oasis-open.org] On > Behalf Of Michael S. Tsirkin > Sent: Sunday, September 10, 2017 1:06 PM > To: virtio-dev at lists.oasis-open.org > Cc: virtualization at lists.linux-foundation.org > Subject: [virtio-dev] packed ring layout proposal v3 > [...] > * Batching descriptors: > > virtio 1.0 allows passing a batch of descriptors in both directions, by incrementing > the used/avail index by values > 1. > At the moment only batching of used descriptors is used. > > We can support this by chaining a list of device descriptors through > VRING_DESC_...

...escriptor. >Thus driver uses DESC_DRIVER to detect that device data in >descriptor is valid. Basically DESC_HW from v2 split in two? > >DESC_WRAP: used by device to poll. Driver sets it to a *different* >value every time it overwrites a descriptor. >How to achieve it? >since descriptors are written out in ring order, >simply maintain the current value internally (start value 1) and flip it >every time you overwrite the first descriptor. >Device leaves it intact when overwriting a descriptor. This is confusing me a bit. My understanding is: 1. the internally kept wrap v...

...escriptor. >Thus driver uses DESC_DRIVER to detect that device data in >descriptor is valid. Basically DESC_HW from v2 split in two? > >DESC_WRAP: used by device to poll. Driver sets it to a *different* >value every time it overwrites a descriptor. >How to achieve it? >since descriptors are written out in ring order, >simply maintain the current value internally (start value 1) and flip it >every time you overwrite the first descriptor. >Device leaves it intact when overwriting a descriptor. This is confusing me a bit. My understanding is: 1. the internally kept wrap v...

...t; > And I think something related to this in the spec isn't very > > clear currently. > > > > In the spec, there are below words: > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > """ > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > is reserved and is ignored by the device. > > """ > > > > So when device writes back an used descriptor in this case, > > device may not set the VIRTQ_DESC_F_WRITE flag as the flag > > is reser...

...t; > And I think something related to this in the spec isn't very > > clear currently. > > > > In the spec, there are below words: > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > """ > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > is reserved and is ignored by the device. > > """ > > > > So when device writes back an used descriptor in this case, > > device may not set the VIRTQ_DESC_F_WRITE flag as the flag > > is reser...

...new features > > --- > > Performance analysis of this is in my kvm forum 2016 presentation. > The idea is to have a r/w descriptor in a ring structure, > replacing the used and available ring, index and descriptor > buffer. > > * Descriptor ring: > > Guest adds descriptors with unique index values and DESC_HW set in flags. > Host overwrites used descriptors with correct len, index, and DESC_HW > clear. Flags are always set/cleared last. > > #define DESC_HW 0x0080 > > struct desc { > __le64 addr; > __le32 len; > __...

...ry > > > > clear currently. > > > > > > > > In the spec, there are below words: > > > > > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > > > """ > > > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > > > is reserved and is ignored by the device. > > > > """ > > > > > > > > So when device writes back an used descriptor in this case, > > > > device may not set the VIRT...

...ry > > > > clear currently. > > > > > > > > In the spec, there are below words: > > > > > > > > https://github.com/oasis-tcs/virtio-spec/blob/d4fec517dfcf/packed-ring.tex#L272 > > > > """ > > > > In descriptors with VIRTQ_DESC_F_INDIRECT set VIRTQ_DESC_F_WRITE > > > > is reserved and is ignored by the device. > > > > """ > > > > > > > > So when device writes back an used descriptor in this case, > > > > device may not set the VIRT...

...ng a > > > descriptor. Device clears it when overwriting a descriptor. > > > Thus driver uses DESC_DRIVER to detect that device data in > > > descriptor is valid. > > > > Basically DESC_HW from v2 split in two? > > Yes in order to avoid overwriting all descriptors. > > > > > > > DESC_WRAP: used by device to poll. Driver sets it to a *different* > > > value every time it overwrites a descriptor. How to achieve it? > > > since descriptors are written out in ring order, simply maintain the > > > current value int...

...ng a > > > descriptor. Device clears it when overwriting a descriptor. > > > Thus driver uses DESC_DRIVER to detect that device data in > > > descriptor is valid. > > > > Basically DESC_HW from v2 split in two? > > Yes in order to avoid overwriting all descriptors. > > > > > > > DESC_WRAP: used by device to poll. Driver sets it to a *different* > > > value every time it overwrites a descriptor. How to achieve it? > > > since descriptors are written out in ring order, simply maintain the > > > current value int...

...bit to change. > > Now driver sees that DRIVER bit has been cleared, so it nows that id is valid. I > sees id 1, therefore id 0 and 1 has been read and are safe to overwrite. > > So it writes it out. It wrapped around to beginning of ring, so it flips the > WRAP bit to 0 on all descriptors now: > > DESC[0].addr = 9ABC > DESC[0].id = 0 > DESC[0].flags = DESC_DRIVER | DESC_NEXT > > > DESC[0].addr = DEF0 > DESC[0].id = 1 > DESC[0].flags = DESC_DRIVER > > > Next round wrap will be 1 again. > > > To summarise: > > DRIVER bit is us...

...bit to change. > > Now driver sees that DRIVER bit has been cleared, so it nows that id is valid. I > sees id 1, therefore id 0 and 1 has been read and are safe to overwrite. > > So it writes it out. It wrapped around to beginning of ring, so it flips the > WRAP bit to 0 on all descriptors now: > > DESC[0].addr = 9ABC > DESC[0].id = 0 > DESC[0].flags = DESC_DRIVER | DESC_NEXT > > > DESC[0].addr = DEF0 > DESC[0].id = 1 > DESC[0].flags = DESC_DRIVER > > > Next round wrap will be 1 again. > > > To summarise: > > DRIVER bit is us...

...; Sent: Sunday, September 10, 2017 1:06 PM > > To: virtio-dev at lists.oasis-open.org > > Cc: virtualization at lists.linux-foundation.org > > Subject: [virtio-dev] packed ring layout proposal v3 > > > [...] > > * Descriptor ring: > > > > Driver writes descriptors with unique index values and DESC_DRIVER set in > > flags. > > Descriptors are written in a ring order: from start to end of ring, wrapping > > around to the beginning. > > Device writes used descriptors with correct len, index, and DESC_HW clear. > > Again descriptors...

...; Sent: Sunday, September 10, 2017 1:06 PM > > To: virtio-dev at lists.oasis-open.org > > Cc: virtualization at lists.linux-foundation.org > > Subject: [virtio-dev] packed ring layout proposal v3 > > > [...] > > * Descriptor ring: > > > > Driver writes descriptors with unique index values and DESC_DRIVER set in > > flags. > > Descriptors are written in a ring order: from start to end of ring, wrapping > > around to the beginning. > > Device writes used descriptors with correct len, index, and DESC_HW clear. > > Again descriptors...

...d virtio layout that might be appropriate for > af_packet as well. Here's the repost (slightly cut down) sorry about the duplicates. The idea is to have a r/w descriptor in a ring structure, replacing the used and available ring, index and descriptor buffer. * Descriptor ring: Guest adds descriptors with unique index values and DESC_HW set in flags. Host overwrites used descriptors with correct len, index, and DESC_HW clear. Flags are always set/cleared last. #define DESC_HW 0x0080 struct desc { __le64 addr; __le32 len; __le16 index; __le16 flags; }; When DE...

...d virtio layout that might be appropriate for > af_packet as well. Here's the repost (slightly cut down) sorry about the duplicates. The idea is to have a r/w descriptor in a ring structure, replacing the used and available ring, index and descriptor buffer. * Descriptor ring: Guest adds descriptors with unique index values and DESC_HW set in flags. Host overwrites used descriptors with correct len, index, and DESC_HW clear. Flags are always set/cleared last. #define DESC_HW 0x0080 struct desc { __le64 addr; __le32 len; __le16 index; __le16 flags; }; When DE...