[RFC PATCH v2] drm/amdgpu/ttm: optimize vram access in amdgpu_ttm_access_memory()
Wang, Kevin(Yang)
Kevin1.Wang at amd.com
Tue Jul 13 08:32:06 UTC 2021
[AMD Official Use Only]
<comments inline>
________________________________
From: Christian König <ckoenig.leichtzumerken at gmail.com>
Sent: Tuesday, July 13, 2021 3:11 PM
To: Wang, Kevin(Yang) <Kevin1.Wang at amd.com>; amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
Cc: Lazar, Lijo <Lijo.Lazar at amd.com>; Deucher, Alexander <Alexander.Deucher at amd.com>; Min, Frank <Frank.Min at amd.com>; Koenig, Christian <Christian.Koenig at amd.com>; Zhang, Hawking <Hawking.Zhang at amd.com>
Subject: Re: [RFC PATCH v2] drm/amdgpu/ttm: optimize vram access in amdgpu_ttm_access_memory()
Am 13.07.21 um 05:23 schrieb Kevin Wang:
> 1. using vram aper to access vram if possible
> 2. avoid MM_INDEX/MM_DATA is not working when mmio protect feature is
> enabled.
>
> Signed-off-by: Kevin Wang <kevin1.wang at amd.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 126 +++++++++++++++++-------
> 1 file changed, 89 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 2aa2eb5de37a..8f6f605bc459 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1407,6 +1407,91 @@ static bool amdgpu_ttm_bo_eviction_valuable(struct ttm_buffer_object *bo,
> return ttm_bo_eviction_valuable(bo, place);
> }
>
> +static void amdgpu_ttm_vram_mm_align_access(struct amdgpu_device *adev, loff_t pos,
> + uint32_t *value, bool write)
Please drop the _vram_ and _align_ part from the name. Just
amdgpu_device_mm_access.
[kevin]: I will correct it in next patch.
> +{
> + unsigned long flags;
> +
> + BUG_ON(!IS_ALIGNED(pos, 4));
> +
> + spin_lock_irqsave(&adev->mmio_idx_lock, flags);
> + WREG32_NO_KIQ(mmMM_INDEX, ((uint32_t)pos) | 0x80000000);
> + WREG32_NO_KIQ(mmMM_INDEX_HI, pos >> 31);
> + if (write)
> + WREG32_NO_KIQ(mmMM_DATA, *value);
> + else
> + *value = RREG32_NO_KIQ(mmMM_DATA);
> + spin_unlock_irqrestore(&adev->mmio_idx_lock, flags);
> +}
That should still be in amdgpu_device.c and you completely messed up the
drm_dev_enter()/drm_dev_exit() annotation.
Looks like you are working on an old branch where that is not yet merged?
[kevin]: yes, I'm working on amd-staging-drm-next branch, the following patch (from drm-next-misc) is not merged into this branch.
drm/amdgpu: Guard against write accesses after device removal
This should prevent writing to memory or IO ranges possibly
already allocated for other uses after our device is removed.
v5:
Protect more places wher memcopy_to/form_io takes place
Protect IB submissions
v6: Switch to !drm_dev_enter instead of scoping entire code
with brackets.
v7:
Drop guard of HW ring commands emission protection since they
are in GART and not in MMIO.
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky at amd.com>
Reviewed-by: Alex Deucher <alexander.deucher at amd.com>
> +
> +static void amdgpu_ttm_vram_mm_access(struct amdgpu_device *adev, loff_t pos,
> + void *buf, size_t size, bool write)
> +{
> + while (size) {
> + uint64_t aligned_pos = ALIGN_DOWN(pos, 4);
> + uint64_t bytes = 4 - (pos & 0x3);
> + uint32_t shift = (pos & 0x3) * 8;
> + uint32_t mask = 0xffffffff << shift;
> + uint32_t value = 0;
> +
> + if (size < bytes) {
> + mask &= 0xffffffff >> (bytes - size) * 8;
> + bytes = size;
> + }
> +
> + if (mask != 0xffffffff) {
> + amdgpu_ttm_vram_mm_align_access(adev, aligned_pos, &value, false);
> + if (write) {
> + value &= ~mask;
> + value |= (*(uint32_t *)buf << shift) & mask;
> + amdgpu_ttm_vram_mm_align_access(adev, aligned_pos, &value, true);
> + } else {
> + value = (value & mask) >> shift;
> + memcpy(buf, &value, bytes);
> + }
> + } else {
> + amdgpu_ttm_vram_mm_align_access(adev, aligned_pos, buf, write);
> + }
> +
> + pos += bytes;
> + buf += bytes;
> + size -= bytes;
> + }
> +}
> +
> +static void amdgpu_ttm_vram_access(struct amdgpu_device *adev, loff_t pos,
> + void *buf, size_t size, bool write)
> +{
> + uint64_t last;
> +
> +#ifdef CONFIG_64BIT
> + last = min(pos + size, adev->gmc.visible_vram_size);
> + if (last > pos) {
> + void __iomem *addr = adev->mman.aper_base_kaddr + pos;
> + size_t count = last - pos;
> +
> + if (write) {
> + memcpy_toio(addr, buf, count);
> + mb();
> + amdgpu_device_flush_hdp(adev, NULL);
> + } else {
> + amdgpu_device_invalidate_hdp(adev, NULL);
> + mb();
> + memcpy_fromio(buf, addr, count);
> + }
> +
> + if (count == size)
> + return;
> +
> + pos += count;
> + buf += count;
> + size -= count;
> + }
> +#endif
I would put this as a separate function into amdgpu_device.c.
But all of this should only be the second step since we need a much
smaller patch for backporting first.
> +
> + amdgpu_ttm_vram_mm_access(adev, pos, buf, size, write);
> +}
> +
> /**
> * amdgpu_ttm_access_memory - Read or Write memory that backs a buffer object.
> *
> @@ -1426,8 +1511,6 @@ static int amdgpu_ttm_access_memory(struct ttm_buffer_object *bo,
> struct amdgpu_bo *abo = ttm_to_amdgpu_bo(bo);
> struct amdgpu_device *adev = amdgpu_ttm_adev(abo->tbo.bdev);
> struct amdgpu_res_cursor cursor;
> - unsigned long flags;
> - uint32_t value = 0;
> int ret = 0;
>
> if (bo->mem.mem_type != TTM_PL_VRAM)
> @@ -1435,41 +1518,10 @@ static int amdgpu_ttm_access_memory(struct ttm_buffer_object *bo,
>
> amdgpu_res_first(&bo->mem, offset, len, &cursor);
> while (cursor.remaining) {
> - uint64_t aligned_pos = cursor.start & ~(uint64_t)3;
> - uint64_t bytes = 4 - (cursor.start & 3);
> - uint32_t shift = (cursor.start & 3) * 8;
> - uint32_t mask = 0xffffffff << shift;
> -
> - if (cursor.size < bytes) {
> - mask &= 0xffffffff >> (bytes - cursor.size) * 8;
> - bytes = cursor.size;
> - }
> -
> - if (mask != 0xffffffff) {
> - spin_lock_irqsave(&adev->mmio_idx_lock, flags);
> - WREG32_NO_KIQ(mmMM_INDEX, ((uint32_t)aligned_pos) | 0x80000000);
> - WREG32_NO_KIQ(mmMM_INDEX_HI, aligned_pos >> 31);
> - value = RREG32_NO_KIQ(mmMM_DATA);
> - if (write) {
> - value &= ~mask;
> - value |= (*(uint32_t *)buf << shift) & mask;
> - WREG32_NO_KIQ(mmMM_DATA, value);
> - }
> - spin_unlock_irqrestore(&adev->mmio_idx_lock, flags);
> - if (!write) {
> - value = (value & mask) >> shift;
> - memcpy(buf, &value, bytes);
> - }
This here is the problematic part and should use
amdgpu_ttm_vram_access() instead.
That should be implemented first since we might need to backport that.
Regards,
Christian.
> - } else {
> - bytes = cursor.size & ~0x3ULL;
> - amdgpu_device_vram_access(adev, cursor.start,
> - (uint32_t *)buf, bytes,
> - write);
> - }
> -
> - ret += bytes;
> - buf = (uint8_t *)buf + bytes;
> - amdgpu_res_next(&cursor, bytes);
> + amdgpu_ttm_vram_access(adev, cursor.start, buf, cursor.size, write);
> + ret += cursor.size;
> + buf += cursor.size;
> + amdgpu_res_next(&cursor, cursor.size);
> }
>
> return ret;
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