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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-19 10:09:22 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-19 10:09:22 -0700 |
| commit | f4cdf7ca9a1fdcca413157df19753f388a5a224e (patch) | |
| tree | 60a31895b2446cd7fa27514e8c2843534a0de0da /tools/virtio/ringtest/ring.c | |
| download | linux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.tar.gz linux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.zip | |
Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-mediagrafted
Pull media updates from Mauro Carvalho Chehab:
- v4l2-core: added ISP statistics support and per-block validation
- v4l2-core: Allow unknown HDR10 white point and luminance
- New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor
- New codec: Milos: VPU v2.0 codec support
- isp driver: gained support for Dreamchip RPPX1 ISP framework
- vsp1 driver: gained support for RZ/T2H and RZ/N2H
- Novalake driver: gained CVS support for new NVL hardware
- dvb-core: fix feed leak on failed DMX_ADD_PID
- several driver fixes, cleanups and minor improvements
* tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits)
media: ipu-bridge: check all DMI entries when overriding sensor rotation
media: v4l2-async: avoid deleting unlinked ASC entry on link error
media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement
media: intel/ipu6: fix async notifier cleanup leak on parse error
media: staging/ipu7: fix async notifier UAF on probe error path
media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path
media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem()
media: rcar-isp: Fix VSPX reference leaks
media: rcar-isp: Release ISPCORE resources
media: i2c: imx415: Release runtime PM reference on VBLANK error
media: i2c: imx415: Return test pattern write errors
media: renesas: vsp1: Declare index variables in for loop statement
media: renesas: vsp1: Make reset control optional to support platforms without a reset line
media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs
media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs
media: nxp: imx8-isi: Add additional 32-bit RGB format support
media: nxp: imx8-isi: Add 16-bit raw Bayer format support
media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams
media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks
media: nxp: imx8-isi: Correct color map between V4L2 and ISI
...
Diffstat (limited to 'tools/virtio/ringtest/ring.c')
| -rw-r--r-- | tools/virtio/ringtest/ring.c | 270 |
1 files changed, 270 insertions, 0 deletions
diff --git a/tools/virtio/ringtest/ring.c b/tools/virtio/ringtest/ring.c new file mode 100644 index 000000000..58e7d33bd --- /dev/null +++ b/tools/virtio/ringtest/ring.c @@ -0,0 +1,270 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2016 Red Hat, Inc. + * Author: Michael S. Tsirkin <mst@redhat.com> + * + * Simple descriptor-based ring. virtio 0.9 compatible event index is used for + * signalling, unconditionally. + */ +#define _GNU_SOURCE +#include "main.h" +#include <stdlib.h> +#include <stdio.h> +#include <string.h> + +/* Next - Where next entry will be written. + * Prev - "Next" value when event triggered previously. + * Event - Peer requested event after writing this entry. + */ +static inline bool need_event(unsigned short event, + unsigned short next, + unsigned short prev) +{ + return (unsigned short)(next - event - 1) < (unsigned short)(next - prev); +} + +/* Design: + * Guest adds descriptors with unique index values and DESC_HW in flags. + * Host overwrites used descriptors with correct len, index, and DESC_HW clear. + * Flags are always set last. + */ +#define DESC_HW 0x1 + +struct desc { + unsigned short flags; + unsigned short index; + unsigned len; + unsigned long long addr; +}; + +/* how much padding is needed to avoid false cache sharing */ +#define HOST_GUEST_PADDING 0x80 + +/* Mostly read */ +struct event { + unsigned short kick_index; + unsigned char reserved0[HOST_GUEST_PADDING - 2]; + unsigned short call_index; + unsigned char reserved1[HOST_GUEST_PADDING - 2]; +}; + +struct data { + void *buf; /* descriptor is writeable, we can't get buf from there */ + void *data; +} *data; + +struct desc *ring; +struct event *event; + +struct guest { + unsigned avail_idx; + unsigned last_used_idx; + unsigned num_free; + unsigned kicked_avail_idx; + unsigned char reserved[HOST_GUEST_PADDING - 12]; +} guest; + +struct host { + /* we do not need to track last avail index + * unless we have more than one in flight. + */ + unsigned used_idx; + unsigned called_used_idx; + unsigned char reserved[HOST_GUEST_PADDING - 4]; +} host; + +/* implemented by ring */ +void alloc_ring(void) +{ + int ret; + int i; + + ret = posix_memalign((void **)&ring, 0x1000, ring_size * sizeof *ring); + if (ret) { + perror("Unable to allocate ring buffer.\n"); + exit(3); + } + event = calloc(1, sizeof(*event)); + if (!event) { + perror("Unable to allocate event buffer.\n"); + exit(3); + } + guest.avail_idx = 0; + guest.kicked_avail_idx = -1; + guest.last_used_idx = 0; + host.used_idx = 0; + host.called_used_idx = -1; + for (i = 0; i < ring_size; ++i) { + struct desc desc = { + .index = i, + }; + ring[i] = desc; + } + guest.num_free = ring_size; + data = calloc(ring_size, sizeof(*data)); + if (!data) { + perror("Unable to allocate data buffer.\n"); + exit(3); + } +} + +/* guest side */ +int add_inbuf(unsigned len, void *buf, void *datap) +{ + unsigned head, index; + + if (!guest.num_free) + return -1; + + guest.num_free--; + head = (ring_size - 1) & (guest.avail_idx++); + + /* Start with a write. On MESI architectures this helps + * avoid a shared state with consumer that is polling this descriptor. + */ + ring[head].addr = (unsigned long)(void*)buf; + ring[head].len = len; + /* read below might bypass write above. That is OK because it's just an + * optimization. If this happens, we will get the cache line in a + * shared state which is unfortunate, but probably not worth it to + * add an explicit full barrier to avoid this. + */ + barrier(); + index = ring[head].index; + data[index].buf = buf; + data[index].data = datap; + /* Barrier A (for pairing) */ + smp_release(); + ring[head].flags = DESC_HW; + + return 0; +} + +void *get_buf(unsigned *lenp, void **bufp) +{ + unsigned head = (ring_size - 1) & guest.last_used_idx; + unsigned index; + void *datap; + + if (ring[head].flags & DESC_HW) + return NULL; + /* Barrier B (for pairing) */ + smp_acquire(); + *lenp = ring[head].len; + index = ring[head].index & (ring_size - 1); + datap = data[index].data; + *bufp = data[index].buf; + data[index].buf = NULL; + data[index].data = NULL; + guest.num_free++; + guest.last_used_idx++; + return datap; +} + +bool used_empty() +{ + unsigned head = (ring_size - 1) & guest.last_used_idx; + + return (ring[head].flags & DESC_HW); +} + +void disable_call() +{ + /* Doing nothing to disable calls might cause + * extra interrupts, but reduces the number of cache misses. + */ +} + +bool enable_call() +{ + event->call_index = guest.last_used_idx; + /* Flush call index write */ + /* Barrier D (for pairing) */ + smp_mb(); + return used_empty(); +} + +void kick_available(void) +{ + bool need; + + /* Flush in previous flags write */ + /* Barrier C (for pairing) */ + smp_mb(); + need = need_event(event->kick_index, + guest.avail_idx, + guest.kicked_avail_idx); + + guest.kicked_avail_idx = guest.avail_idx; + if (need) + kick(); +} + +/* host side */ +void disable_kick() +{ + /* Doing nothing to disable kicks might cause + * extra interrupts, but reduces the number of cache misses. + */ +} + +bool enable_kick() +{ + event->kick_index = host.used_idx; + /* Barrier C (for pairing) */ + smp_mb(); + return avail_empty(); +} + +bool avail_empty() +{ + unsigned head = (ring_size - 1) & host.used_idx; + + return !(ring[head].flags & DESC_HW); +} + +bool use_buf(unsigned *lenp, void **bufp) +{ + unsigned head = (ring_size - 1) & host.used_idx; + + if (!(ring[head].flags & DESC_HW)) + return false; + + /* make sure length read below is not speculated */ + /* Barrier A (for pairing) */ + smp_acquire(); + + /* simple in-order completion: we don't need + * to touch index at all. This also means we + * can just modify the descriptor in-place. + */ + ring[head].len--; + /* Make sure len is valid before flags. + * Note: alternative is to write len and flags in one access - + * possible on 64 bit architectures but wmb is free on Intel anyway + * so I have no way to test whether it's a gain. + */ + /* Barrier B (for pairing) */ + smp_release(); + ring[head].flags = 0; + host.used_idx++; + return true; +} + +void call_used(void) +{ + bool need; + + /* Flush in previous flags write */ + /* Barrier D (for pairing) */ + smp_mb(); + + need = need_event(event->call_index, + host.used_idx, + host.called_used_idx); + + host.called_used_idx = host.used_idx; + + if (need) + call(); +} |
