| Message ID | 20220420150942.31235-10-jgross@suse.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xen: simplify frontend side ring setup | expand |
On 4/20/22 11:09 AM, Juergen Gross wrote: > > +/* > + * xenbus_setup_ring > + * @dev: xenbus device > + * @vaddr: pointer to starting virtual address of the ring > + * @nr_pages: number of pages to be granted > + * @grefs: grant reference array to be filled in > + * > + * Allocate physically contiguous pages for a shared ring buffer and grant it > + * to the peer of the given device. The ring buffer is initially filled with > + * zeroes. The virtual address of the ring is stored at @vaddr and the > + * grant references are stored in the @grefs array. In case of error @vaddr > + * will be set to NULL and @grefs will be filled with INVALID_GRANT_REF. > + */ > +int xenbus_setup_ring(struct xenbus_device *dev, gfp_t gfp, void **vaddr, > + unsigned int nr_pages, grant_ref_t *grefs) > +{ > + unsigned long ring_size = nr_pages * XEN_PAGE_SIZE; > + unsigned int i; > + int ret; > + > + *vaddr = alloc_pages_exact(ring_size, gfp | __GFP_ZERO); > + if (!*vaddr) { > + ret = -ENOMEM; > + goto err; > + } > + > + ret = xenbus_grant_ring(dev, *vaddr, nr_pages, grefs); > + if (ret) > + goto err; > + > + return 0; > + > + err: > + if (*vaddr) > + free_pages_exact(*vaddr, ring_size); > + for (i = 0; i < nr_pages; i++) > + grefs[i] = INVALID_GRANT_REF; > + *vaddr = NULL; > + > + return ret; > +} We can create a wrapper around this function that will also call SHARED_RING_INIT() and FRONT_RING_INIT(). A bunch of drivers do that. -boris
On 20.04.22 20:44, Boris Ostrovsky wrote: > > On 4/20/22 11:09 AM, Juergen Gross wrote: >> +/* >> + * xenbus_setup_ring >> + * @dev: xenbus device >> + * @vaddr: pointer to starting virtual address of the ring >> + * @nr_pages: number of pages to be granted >> + * @grefs: grant reference array to be filled in >> + * >> + * Allocate physically contiguous pages for a shared ring buffer and grant it >> + * to the peer of the given device. The ring buffer is initially filled with >> + * zeroes. The virtual address of the ring is stored at @vaddr and the >> + * grant references are stored in the @grefs array. In case of error @vaddr >> + * will be set to NULL and @grefs will be filled with INVALID_GRANT_REF. >> + */ >> +int xenbus_setup_ring(struct xenbus_device *dev, gfp_t gfp, void **vaddr, >> + unsigned int nr_pages, grant_ref_t *grefs) >> +{ >> + unsigned long ring_size = nr_pages * XEN_PAGE_SIZE; >> + unsigned int i; >> + int ret; >> + >> + *vaddr = alloc_pages_exact(ring_size, gfp | __GFP_ZERO); >> + if (!*vaddr) { >> + ret = -ENOMEM; >> + goto err; >> + } >> + >> + ret = xenbus_grant_ring(dev, *vaddr, nr_pages, grefs); >> + if (ret) >> + goto err; >> + >> + return 0; >> + >> + err: >> + if (*vaddr) >> + free_pages_exact(*vaddr, ring_size); >> + for (i = 0; i < nr_pages; i++) >> + grefs[i] = INVALID_GRANT_REF; >> + *vaddr = NULL; >> + >> + return ret; >> +} > > > We can create a wrapper around this function that will also call > SHARED_RING_INIT() and FRONT_RING_INIT(). A bunch of drivers do that. This wrapper would need to be a macro, so I decided not to do that. It would make sense to merge the call of SHARED_RING_INIT() into FRONT_RING_INIT() (or better, have a new macro combining the two), though, as there is no use case of FRONT_RING_INIT() without a call of SHARED_RING_INIT() directly before it. Juergen
diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c index df6890681231..1a2e0d94ccd1 100644 --- a/drivers/xen/xenbus/xenbus_client.c +++ b/drivers/xen/xenbus/xenbus_client.c @@ -407,6 +407,75 @@ int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr, } EXPORT_SYMBOL_GPL(xenbus_grant_ring); +/* + * xenbus_setup_ring + * @dev: xenbus device + * @vaddr: pointer to starting virtual address of the ring + * @nr_pages: number of pages to be granted + * @grefs: grant reference array to be filled in + * + * Allocate physically contiguous pages for a shared ring buffer and grant it + * to the peer of the given device. The ring buffer is initially filled with + * zeroes. The virtual address of the ring is stored at @vaddr and the + * grant references are stored in the @grefs array. In case of error @vaddr + * will be set to NULL and @grefs will be filled with INVALID_GRANT_REF. + */ +int xenbus_setup_ring(struct xenbus_device *dev, gfp_t gfp, void **vaddr, + unsigned int nr_pages, grant_ref_t *grefs) +{ + unsigned long ring_size = nr_pages * XEN_PAGE_SIZE; + unsigned int i; + int ret; + + *vaddr = alloc_pages_exact(ring_size, gfp | __GFP_ZERO); + if (!*vaddr) { + ret = -ENOMEM; + goto err; + } + + ret = xenbus_grant_ring(dev, *vaddr, nr_pages, grefs); + if (ret) + goto err; + + return 0; + + err: + if (*vaddr) + free_pages_exact(*vaddr, ring_size); + for (i = 0; i < nr_pages; i++) + grefs[i] = INVALID_GRANT_REF; + *vaddr = NULL; + + return ret; +} +EXPORT_SYMBOL_GPL(xenbus_setup_ring); + +/* + * xenbus_teardown_ring + * @vaddr: starting virtual address of the ring + * @nr_pages: number of pages + * @grefs: grant reference array + * + * Remove grants for the shared ring buffer and free the associated memory. + * On return the grant reference array is filled with INVALID_GRANT_REF. + */ +void xenbus_teardown_ring(void **vaddr, unsigned int nr_pages, + grant_ref_t *grefs) +{ + unsigned int i; + + for (i = 0; i < nr_pages; i++) { + if (grefs[i] != INVALID_GRANT_REF) { + gnttab_end_foreign_access(grefs[i], 0); + grefs[i] = INVALID_GRANT_REF; + } + } + + if (*vaddr) + free_pages_exact(*vaddr, nr_pages * XEN_PAGE_SIZE); + *vaddr = NULL; +} +EXPORT_SYMBOL_GPL(xenbus_teardown_ring); /** * Allocate an event channel for the given xenbus_device, assigning the newly diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h index b13eb86395e0..b533b4adc835 100644 --- a/include/xen/xenbus.h +++ b/include/xen/xenbus.h @@ -226,6 +226,10 @@ int xenbus_watch_pathfmt(struct xenbus_device *dev, struct xenbus_watch *watch, int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state new_state); int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr, unsigned int nr_pages, grant_ref_t *grefs); +int xenbus_setup_ring(struct xenbus_device *dev, gfp_t gfp, void **vaddr, + unsigned int nr_pages, grant_ref_t *grefs); +void xenbus_teardown_ring(void **vaddr, unsigned int nr_pages, + grant_ref_t *grefs); int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs, unsigned int nr_grefs, void **vaddr);
Most PV device frontends share very similar code for setting up shared ring buffers: - allocate page(s) - init the ring admin data - give the backend access to the ring via grants Tearing down the ring requires similar actions in all frontends again: - remove grants - free the page(s) Provide service functions xenbus_setup_ring() and xenbus_teardown_ring() for that purpose. Signed-off-by: Juergen Gross <jgross@suse.com> --- drivers/xen/xenbus/xenbus_client.c | 69 ++++++++++++++++++++++++++++++ include/xen/xenbus.h | 4 ++ 2 files changed, 73 insertions(+)