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// SPDX-License-Identifier: BSD-3-Clause
/*
* frame_producer.cu - render an animated frame on the guest GPU and publish
* it into the ivshmem (kvmfr) BAR so the host can see a real GPU-rendered
* frame from the guest.
*
* Path: CUDA kernel -> device buffer -> host buffer -> ivshmem BAR
* (/sys/bus/pci/devices/0000:00:03.0/resource2, the 128 MiB kvmfr
* device QEMU backs with /dev/shm/kvmfr-<uuid>).
*
* Layout in the BAR (offset 0x100000, clear of the kvmfr protocol header):
* struct frame_hdr { magic, version, width, height, stride, format, seq }
* then width*height*4 bytes of RGBA8.
*
* Usage: sudo ./frame_producer [frames] [width] [height] [fps]
* Prints: FRAME seq=<n> ms=<render+copy ms> (one line per frame, first 5 and
* every 30th) and FRAME_DONE frames=<n>.
*/
#include <cstdio>
#include <cstdlib>
#include <cstdint>
#include <cstring>
#include <ctime>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <cuda_runtime.h>
#define CHECK(x) \
do { \
cudaError_t e_ = (x); \
if (e_ != cudaSuccess) { \
printf("CUDA_ERROR %s at line %d\n", \
cudaGetErrorString(e_), __LINE__); \
return 1; \
} \
} while (0)
#define FRAME_OFFSET 0x100000UL
#define HDR_MAGIC 0x4b564d46u /* "FMVK" little-endian-ish */
struct frame_hdr {
uint32_t magic;
uint32_t version;
uint32_t width;
uint32_t height;
uint32_t stride;
uint32_t format; /* 0 = RGBA8 */
uint32_t seq;
uint32_t reserved;
uint64_t timestamp_ns;
};
__global__ void render_julia(uchar4 *fb, int w, int h, float t)
{
int x = blockIdx.x * blockDim.x + threadIdx.x;
int y = blockIdx.y * blockDim.y + threadIdx.y;
if (x >= w || y >= h)
return;
float fx = (x - w * 0.5f) / (h * 0.45f);
float fy = (y - h * 0.5f) / (h * 0.45f);
float cr = 0.7885f * cosf(t);
float ci = 0.7885f * sinf(t);
float zr = fx, zi = fy;
int it = 0;
const int maxit = 96;
while (zr * zr + zi * zi < 4.0f && it < maxit) {
float nzr = zr * zr - zi * zi + cr;
float nzi = 2.0f * zr * zi + ci;
zr = nzr;
zi = nzi;
it++;
}
{
float v = (float)it / (float)maxit;
unsigned char r = (unsigned char)(255.0f * v);
unsigned char g = (unsigned char)(255.0f * (1.0f - v) * v * 4.0f);
unsigned char b = (unsigned char)(255.0f * (1.0f - v));
unsigned char a = 255;
fb[y * w + x] = make_uchar4(r, g, b, a);
}
}
static uint64_t now_ns(void)
{
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
return (uint64_t)ts.tv_sec * 1000000000ull + ts.tv_nsec;
}
int main(int argc, char **argv)
{
int frames = argc > 1 ? atoi(argv[1]) : 60;
int w = argc > 2 ? atoi(argv[2]) : 800;
int h = argc > 3 ? atoi(argv[3]) : 600;
int fps = argc > 4 ? atoi(argv[4]) : 10;
const char *bar_path =
"/sys/bus/pci/devices/0000:00:03.0/resource2";
size_t fb_bytes = (size_t)w * h * 4;
uchar4 *d_fb = NULL, *h_fb = NULL;
unsigned char *bar;
struct frame_hdr *hdr;
volatile uint32_t *seqp;
int fd, i;
setvbuf(stdout, NULL, _IONBF, 0);
fd = open(bar_path, O_RDWR | O_SYNC);
if (fd < 0) {
printf("OPEN_FAIL %s\n", bar_path);
return 1;
}
bar = (unsigned char *)mmap(NULL, 128UL << 20, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);
if (bar == MAP_FAILED) {
printf("MMAP_FAIL\n");
return 1;
}
hdr = (struct frame_hdr *)(bar + FRAME_OFFSET);
seqp = &hdr->seq;
CHECK(cudaMalloc(&d_fb, fb_bytes));
h_fb = (uchar4 *)malloc(fb_bytes);
if (!h_fb) {
printf("HOST_ALLOC_FAIL\n");
return 1;
}
hdr->magic = HDR_MAGIC;
hdr->version = 1;
hdr->width = (uint32_t)w;
hdr->height = (uint32_t)h;
hdr->stride = (uint32_t)w * 4;
hdr->format = 0;
for (i = 0; i < frames; i++) {
uint64_t t0 = now_ns();
float phase = (float)i * 0.15f;
dim3 block(16, 16);
dim3 grid((w + 15) / 16, (h + 15) / 16);
render_julia<<<grid, block>>>(d_fb, w, h, phase);
CHECK(cudaGetLastError());
CHECK(cudaDeviceSynchronize());
CHECK(cudaMemcpy(h_fb, d_fb, fb_bytes,
cudaMemcpyDeviceToHost));
memcpy(bar + FRAME_OFFSET + sizeof(struct frame_hdr), h_fb,
fb_bytes);
hdr->timestamp_ns = now_ns();
__sync_synchronize();
*seqp = (uint32_t)(i + 1);
__sync_synchronize();
if (i < 5 || (i % 30) == 29)
printf("FRAME seq=%d ms=%.1f\n", i + 1,
(double)(now_ns() - t0) / 1e6);
if (fps > 0)
usleep((useconds_t)(1000000 / fps));
}
printf("FRAME_DONE frames=%d %dx%d\n", frames, w, h);
CHECK(cudaFree(d_fb));
free(h_fb);
munmap(bar, 128UL << 20);
close(fd);
return 0;
}
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