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authorAlexey Kardashevskiy <aik@ozlabs.ru>2018-12-19 19:52:29 +1100
committerMichael Ellerman <mpe@ellerman.id.au>2018-12-21 16:20:46 +1100
commit58629c0dc34904d135af944d120eb23165ec3b61 (patch)
treec6e96ae78213fc95c6f7181047ee68210d6440d1 /arch/powerpc
parent135ef954051b102870a8d47a8eb822af1f1b1ec1 (diff)
powerpc/powernv/npu: Fault user page into the hypervisor's pagetable
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> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/platforms/powernv/npu-dma.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
index b713727663e2..d7f742ed48ba 100644
--- a/arch/powerpc/platforms/powernv/npu-dma.c
+++ b/arch/powerpc/platforms/powernv/npu-dma.c
@@ -1132,6 +1132,8 @@ 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;
@@ -1144,18 +1146,17 @@ 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]);
}