Am 19.01.2017 um 14:51 schrieb Grazvydas Ignotas: > On Thu, Jan 19, 2017 at 11:10 AM, Christian König > <deathsimple at vodafone.de> wrote: >> Am 18.01.2017 um 12:42 schrieb Monk Liu: >>> @@ -6743,6 +6741,15 @@ static void gfx_v8_ring_emit_cntxcntl(struct >>> amdgpu_ring *ring, uint32_t flags) >>> if (amdgpu_sriov_vf(ring->adev)) >>> gfx_v8_0_ring_emit_de_meta_init(ring, >>> (flags & AMDGPU_VM_DOMAIN) ? AMDGPU_CSA_VADDR : >>> ring->adev->virt.csa_vmid0_addr); >>> + >>> + /* We need to pad some NOPs before emit_ib to prevent CE run ahead >>> of >>> + * vm_flush, which may trigger VM fault. */ >>> + if (ring->wptr > ring->last_vm_flush_pos) /* no wptr wrapping to >>> RB head */ >>> + amdgpu_ring_insert_nop(ring, 128 - (ring->wptr - >>> ring->last_vm_flush_pos)); >> >> This can easily result in a negative number, couldn't it? >> >>> + else >>> + if (ring->ptr_mask + 1 - ring->last_vm_flush_pos + >>> ring->wptr < 128) >>> + amdgpu_ring_insert_nop(ring, >>> + 128 - (ring->ptr_mask + 1 - >>> ring->last_vm_flush_pos + ring->wptr)); >> >> I think it would be cleaner if you calculate the number of NOPs needed first >> for both cases and then check if the number isn't negative for both cases. > What about this: > 128 - ((ring->wptr - ring->last_vm_flush_pos) & 127) That won't handle the case for negative nop count correctly either. See when we already emitted more than 128 dw we don't want to add some more. Christian. > > Gražvydas
