@@ -1133,6 +1133,8 @@ int pnv_npu2_handle_fault(struct npu_context *context, uintptr_t *ea,
u64 rc = 0, result = 0;
int i, is_write;
struct page *page[1];
+ const char __user *u;
+ char c;
/* mmap_sem should be held so the struct_mm must be present */
struct mm_struct *mm = context->mm;
@@ -1145,18 +1147,17 @@ int pnv_npu2_handle_fault(struct npu_context *context, uintptr_t *ea,
is_write ? FOLL_WRITE : 0,
page, NULL, NULL);
- /*
- * To support virtualised environments we will have to do an
- * access to the page to ensure it gets faulted into the
- * hypervisor. For the moment virtualisation is not supported in
- * other areas so leave the access out.
- */
if (rc != 1) {
status[i] = rc;
result = -EFAULT;
continue;
}
+ /* Make sure partition scoped tree gets a pte */
+ u = page_address(page[0]);
+ if (__get_user(c, u))
+ result = -EFAULT;
+
status[i] = 0;
put_page(page[0]);
}
When a page fault happens in a GPU, the GPU signals the OS and the GPU driver calls the fault handler which populated a page table; this allows the GPU to complete an ATS request. On the bare metal get_user_pages() is enough as it adds a pte to the kernel page table but under KVM the partition scope tree does not get updated so ATS will still fail. This reads a byte from an effective address which causes HV storage interrupt and KVM updates the partition scope tree. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> --- arch/powerpc/platforms/powernv/npu-dma.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)