Am 2022-09-09 um 11:42 schrieb Philip Yang:
On 2022-09-09 11:13, Felix Kuehling wrote:
Am 2022-09-09 um 09:12 schrieb Philip Yang:
migrate_vma_setup shows below warning because we don't hold another
process mm mmap_lock. We should use current vmf->vma->vm_mm instead,
the
caller already hold current mmap lock inside CPU page fault handler.
WARNING: CPU: 10 PID: 3054 at include/linux/mmap_lock.h:155 find_vma
Call Trace:
walk_page_range+0x76/0x150
migrate_vma_setup+0x18a/0x640
svm_migrate_vram_to_ram+0x245/0xa10 [amdgpu]
svm_migrate_to_ram+0x36f/0x470 [amdgpu]
do_swap_page+0xcfe/0xec0
__handle_mm_fault+0x96b/0x15e0
handle_mm_fault+0x13f/0x3e0
do_user_addr_fault+0x1e7/0x690
Fixes: 5e5bbf36a2c0 ("drm/amdkfd: handle CPU fault on COW mapping")
Signed-off-by: Philip Yang <Philip.Yang@xxxxxxx>
For a quick fix, this looks OK.
Reviewed-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
For a better fix, I notice that svm_migrate_vram_to_ram only uses the
mm to look up the vma. But you already know the vma here, so that
look up is completely unnecessary. So could you just call
svm_migrate_vma_to_ram directly? Then you don't need the mm at all
and you save yourself an unnecessary vma lookup from the virtual
address.
Thanks, call svm_migrate_vma_to_ram directly works, that was my first
approach, but the prange we want to migrate may include multiple vma,
it is safer to call svm_migrate_vram_to_ram to handle this case.
Is that because we always try to migrate 2MB at a time, which may span
more than one VMA? I think we could probably limit this to a single VMA
for the page fault case. Separate VMAs are most likely separate
allocations. Migrating them together due to a single page fault is
likely unintentional.
But I agree, that should be a separate patch if we want to change that.
We can tackle that as part of a bigger migration optimization. There is
another item on my TODO list to get rid of splitting ranges by
granularity and use partial migrations instead.
Thanks,
Felix
Regards,
Philip
Regards,
Felix
---
drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
index f62c4561f0f4..1cfa4fcd28b3 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
@@ -947,7 +947,8 @@ static vm_fault_t svm_migrate_to_ram(struct
vm_fault *vmf)
goto out_unlock_prange;
}
- r = svm_migrate_vram_to_ram(prange, mm,
KFD_MIGRATE_TRIGGER_PAGEFAULT_CPU);
+ r = svm_migrate_vram_to_ram(prange, vmf->vma->vm_mm,
+ KFD_MIGRATE_TRIGGER_PAGEFAULT_CPU);
if (r)
pr_debug("failed %d migrate svms 0x%p range 0x%p [0x%lx
0x%lx]\n",
r, prange->svms, prange, prange->start, prange->last);
