英文:
VFIO PCIe BAR write won't work. Register value falls back when program execution finished
问题
我使用以下代码来通过VFIO_PCI API测试PCIe BAR寄存器的写入。
然而,只有在程序仍在运行时,写入才会生效。在程序执行完成后,该值总是回退。
我已验证这不是因为缓存,因为只要程序仍在运行,我可以在FPGA中看到寄存器值的变化。
我的问题是:我应该怎么做才能使我的写入持久化?
英文:
I am using the following code to test a PCIe BAR register write through VFIO_PCI APIs.
` struct vfio_group_status group_status = { .argsz = sizeof(group_status) };
struct vfio_device_info device_info = { .argsz = sizeof(device_info) };
struct vfio_region_info reg = { .argsz = sizeof(reg) };
int container = open("/dev/vfio/vfio", O_RDWR);
int group = open("/dev/vfio/17", O_RDWR);
/* Add the group to the container */
ioctl(group, VFIO_GROUP_SET_CONTAINER, &container);
/* Enable the IOMMU model we want */
ioctl(container, VFIO_SET_IOMMU, VFIO_TYPE1_IOMMU);
int dev = ioctl(group, VFIO_GROUP_GET_DEVICE_FD, "0000:02:00.0");
void* ptr;
ptr = mmap(0, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, dev, ( 0UL << 40));
cout << *((unsigned int *)ptr + 0x202) << endl; //this always print out 0
*((unsigned int *)ptr + 0x202) = 4; //write 4
cout << *((unsigned int *)ptr + 0x202) << endl;` //this always print out 4
However, the write will take effect only if the program is still running. After the program execution finished, the value always falls back.
I have verified this is not because of cache, because I can see the register value change in the FPGA while the program is still running.
My question is: what can I do to make my write persistent?
答案1
得分: 0
我发现了这个相关帖子。显然,这是一种预期的行为:如果使用VFIO-PCI来控制PCIe设备。 "vfio_pci_try_bus_reset"将在进程完成时被调用。导致设备被重置。如帖子中所述,如果可以添加一个模块参数来绕过重置,那将非常好。但到目前为止,似乎还没有这个参数。
英文:
For any one who might encouter with this in the future.
I found this related post. Apparently, this is an expected behavior: if VFIO-PCI is used to control a PCIe device. "vfio_pci_try_bus_reset" will be called upon a process finished. Causing the device to be reset. As mentioned in the post, it would be nice if a module parameter can be added to by pass the reset. But so far it seems that the parameter is not there yet.
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库,让每个人都能够通过互相帮助和分享经验来进步。
评论