Re: [PATCH v1 4/4] vfio/nvgpu: register device memory for poison handling

Alex Williamson
2023-09-28T19:46:50Z

On Wed, 20 Sep 2023 19:32:10 +0530
<ankita@nvidia.com> wrote:

> From: Ankit Agrawal <ankita@nvidia.com>
>
> The nvgrace-gpu-vfio-pci module [1] maps the device memory to the user VA
> (Qemu) using remap_pfn_range() without adding the memory to the kernel.
> The device memory pages are not backed by struct page. Patches 1-3
> implements the mechanism to handle ECC/poison on memory page without
> struct page and expose a registration function. This new mechanism is
> leveraged here.
>
> The module registers its memory region with the kernel MM for ECC handling
> using the register_pfn_address_space() registration API exposed by the
> kernel. It also defines a failure callback function pfn_memory_failure()
> to get the poisoned PFN from the MM.
>
> The module track poisoned PFN as a bitmap with a bit per PFN. The PFN is
> communicated by the kernel MM to the module through the failure function,
> which sets the appropriate bit in the bitmap.
>
> The module also defines a VMA fault ops for the module. It returns
> VM_FAULT_HWPOISON in case the bit for the PFN is set in the bitmap.
>
> [1] https://lore.kernel.org/all/20230915025415.6762-1-ankita@nvidia.com/
>
> Signed-off-by: Ankit Agrawal <ankita@nvidia.com>
> ---
> drivers/vfio/pci/nvgrace-gpu/main.c | 107 +++++++++++++++++++++++++++-
> drivers/vfio/vfio.h | 11 ---
> drivers/vfio/vfio_main.c | 3 +-
> include/linux/vfio.h | 15 ++++
> 4 files changed, 123 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/vfio/pci/nvgrace-gpu/main.c b/drivers/vfio/pci/nvgrace-gpu/main.c
> index ba323f2d8ea1..1c89ce0cc1cc 100644
> --- a/drivers/vfio/pci/nvgrace-gpu/main.c
> +++ b/drivers/vfio/pci/nvgrace-gpu/main.c
> @@ -6,6 +6,10 @@
> #include <linux/pci.h>
> #include <linux/vfio_pci_core.h>
> #include <linux/vfio.h>
> +#ifdef CONFIG_MEMORY_FAILURE
> +#include <linux/bitmap.h>
> +#include <linux/memory-failure.h>
> +#endif
>
> struct nvgrace_gpu_vfio_pci_core_device {
> struct vfio_pci_core_device core_device;
> @@ -13,8 +17,85 @@ struct nvgrace_gpu_vfio_pci_core_device {
> size_t memlength;
> void *memmap;
> struct mutex memmap_lock;
> +#ifdef CONFIG_MEMORY_FAILURE
> + struct pfn_address_space pfn_address_space;
> + unsigned long *pfn_bitmap;
> +#endif
> };
>
> +#ifdef CONFIG_MEMORY_FAILURE
> +void nvgrace_gpu_vfio_pci_pfn_memory_failure(struct pfn_address_space *pfn_space,
> + unsigned long pfn)
> +{
> + struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
> + pfn_space, struct nvgrace_gpu_vfio_pci_core_device, pfn_address_space);
> + unsigned long mem_offset = pfn - pfn_space->node.start;
> +
> + if (mem_offset >= nvdev->memlength)
> + return;
> +
> + /*
> + * MM has called to notify a poisoned page. Track that in the bitmap.
> + */
> + __set_bit(mem_offset, nvdev->pfn_bitmap);
> +}
> +
> +struct pfn_address_space_ops nvgrace_gpu_vfio_pci_pas_ops = {
> + .failure = nvgrace_gpu_vfio_pci_pfn_memory_failure,
> +};
> +
> +static int
> +nvgrace_gpu_vfio_pci_register_pfn_range(struct nvgrace_gpu_vfio_pci_core_device *nvdev,
> + struct vm_area_struct *vma)
> +{
> + unsigned long nr_pages;
> + int ret = 0;
> +
> + nr_pages = nvdev->memlength >> PAGE_SHIFT;
> +
> + nvdev->pfn_address_space.node.start = vma->vm_pgoff;
> + nvdev->pfn_address_space.node.last = vma->vm_pgoff + nr_pages - 1;
> + nvdev->pfn_address_space.ops = &nvgrace_gpu_vfio_pci_pas_ops;
> + nvdev->pfn_address_space.mapping = vma->vm_file->f_mapping;
> +
> + ret = register_pfn_address_space(&(nvdev->pfn_address_space));
> +
> + return ret;
> +}
> +
> +static vm_fault_t nvgrace_gpu_vfio_pci_fault(struct vm_fault *vmf)
> +{
> + unsigned long mem_offset = vmf->pgoff - vmf->vma->vm_pgoff;
> + struct vfio_device *core_vdev;
> + struct nvgrace_gpu_vfio_pci_core_device *nvdev;
> +
> + if (!(vmf->vma->vm_file))
> + goto error_exit;
> +
> + core_vdev = vfio_device_from_file(vmf->vma->vm_file);
> +
> + if (!core_vdev)
> + goto error_exit;
> +
> + nvdev = container_of(core_vdev,
> + struct nvgrace_gpu_vfio_pci_core_device, core_device.vdev);
> +
> + /*
> + * Check if the page is poisoned.
> + */
> + if (mem_offset < (nvdev->memlength >> PAGE_SHIFT) &&
> + test_bit(mem_offset, nvdev->pfn_bitmap))
> + return VM_FAULT_HWPOISON;
> +
> +error_exit:
> + return VM_FAULT_ERROR;
> +}
> +
> +static const struct vm_operations_struct nvgrace_gpu_vfio_pci_mmap_ops = {
> + .fault = nvgrace_gpu_vfio_pci_fault,
> +};
> +#endif
> +
> static int nvgrace_gpu_vfio_pci_open_device(struct vfio_device *core_vdev)
> {
> struct vfio_pci_core_device *vdev =
> @@ -46,6 +127,9 @@ static void nvgrace_gpu_vfio_pci_close_device(struct vfio_device *core_vdev)
>
> mutex_destroy(&nvdev->memmap_lock);
>
> +#ifdef CONFIG_MEMORY_FAILURE
> + unregister_pfn_address_space(&(nvdev->pfn_address_space));
> +#endif
> vfio_pci_core_close_device(core_vdev);
> }
>
> @@ -104,8 +188,12 @@ static int nvgrace_gpu_vfio_pci_mmap(struct vfio_device *core_vdev,
> return ret;
>
> vma->vm_pgoff = start_pfn;
> +#ifdef CONFIG_MEMORY_FAILURE
> + vma->vm_ops = &nvgrace_gpu_vfio_pci_mmap_ops;
>
> - return 0;
> + ret = nvgrace_gpu_vfio_pci_register_pfn_range(nvdev, vma);
> +#endif
> + return ret;
> }
>
> static long
> @@ -406,6 +494,19 @@ nvgrace_gpu_vfio_pci_fetch_memory_property(struct pci_dev *pdev,
>
> nvdev->memlength = memlength;
>
> +#ifdef CONFIG_MEMORY_FAILURE
> + /*
> + * A bitmap is maintained to track the pages that are poisoned. Each
> + * page is represented by a bit. Allocation size in bytes is
> + * determined by shifting the device memory size by PAGE_SHIFT to
> + * determine the number of pages; and further shifted by 3 as each
> + * byte could track 8 pages.
> + */
> + nvdev->pfn_bitmap
> + = vzalloc((nvdev->memlength >> PAGE_SHIFT)/BITS_PER_TYPE(char));
> + if (!nvdev->pfn_bitmap)
> + ret = -ENOMEM;
> +#endif
> return ret;
> }
>
> @@ -442,6 +543,10 @@ static void nvgrace_gpu_vfio_pci_remove(struct pci_dev *pdev)
> struct nvgrace_gpu_vfio_pci_core_device *nvdev = nvgrace_gpu_drvdata(pdev);
> struct vfio_pci_core_device *vdev = &nvdev->core_device;
>
> +#ifdef CONFIG_MEMORY_FAILURE
> + vfree(nvdev->pfn_bitmap);
> +#endif
> +
> vfio_pci_core_unregister_device(vdev);
> vfio_put_device(&vdev->vdev);
> }
> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
> index 307e3f29b527..747094503909 100644
> --- a/drivers/vfio/vfio.h
> +++ b/drivers/vfio/vfio.h
> @@ -16,17 +16,6 @@ struct iommufd_ctx;
> struct iommu_group;
> struct vfio_container;
>
> -struct vfio_device_file {
> - struct vfio_device *device;
> - struct vfio_group *group;
> -
> - u8 access_granted;
> - u32 devid; /* only valid when iommufd is valid */
> - spinlock_t kvm_ref_lock; /* protect kvm field */
> - struct kvm *kvm;
> - struct iommufd_ctx *iommufd; /* protected by struct vfio_device_set::lock */
> -};
> -
> void vfio_device_put_registration(struct vfio_device *device);
> bool vfio_device_try_get_registration(struct vfio_device *device);
> int vfio_df_open(struct vfio_device_file *df);
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 40732e8ed4c6..a7dafd7c64a6 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -1309,7 +1309,7 @@ const struct file_operations vfio_device_fops = {
> .mmap = vfio_device_fops_mmap,
> };
>
> -static struct vfio_device *vfio_device_from_file(struct file *file)
> +struct vfio_device *vfio_device_from_file(struct file *file)
> {
> struct vfio_device_file *df = file->private_data;
>
> @@ -1317,6 +1317,7 @@ static struct vfio_device *vfio_device_from_file(struct file *file)
> return NULL;
> return df->device;
> }
> +EXPORT_SYMBOL_GPL(vfio_device_from_file);
>
> /**
> * vfio_file_is_valid - True if the file is valid vfio file
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 454e9295970c..d88af251e931 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -361,4 +361,19 @@ int vfio_virqfd_enable(void *opaque, int (*handler)(void *, void *),
> struct virqfd **pvirqfd, int fd);
> void vfio_virqfd_disable(struct virqfd **pvirqfd);
>
> +/*
> + * VFIO device file.
> + */
> +struct vfio_device_file {
> + struct vfio_device *device;
> + struct vfio_group *group;
> + u8 access_granted;
> + u32 devid; /* only valid when iommufd is valid */
> + spinlock_t kvm_ref_lock; /* protect kvm field */
> + struct kvm *kvm;
> + struct iommufd_ctx *iommufd; /* protected by struct vfio_device_set::lock */
> +};

What here necessitates moving this to the more public header? Thanks,

Alex

> +
> +struct vfio_device *vfio_device_from_file(struct file *file);
> +
> #endif /* VFIO_H */