Hi Felix
Many thanks for your review. I have modified it according to your comments and suggestion.
Best Regards
Yintian Tao
-----Original Message-----
From: Kuehling, Felix <Felix.Kuehling@xxxxxxx>
Sent: 2020年4月17日 23:39
To: Tao, Yintian <Yintian.Tao@xxxxxxx>; Liu, Monk <Monk.Liu@xxxxxxx>
Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [PATCH] drm/amdgpu: refine kiq read register
Am 2020-04-17 um 2:53 a.m. schrieb Yintian Tao:
> According to the current kiq read register method, there will be race
> condition when using KIQ to read register if multiple clients want to
> read at same time just like the expample below:
> 1. client-A start to read REG-0 throguh KIQ 2. client-A poll the
> seqno-0 3. client-B start to read REG-1 through KIQ 4. client-B poll
> the seqno-1 5. the kiq complete these two read operation 6. client-A
> to read the register at the wb buffer and
> get REG-1 value
>
> Therefore, directly make kiq write the register value at the ring
> buffer then there will be no race condition for the wb buffer.
>
> v2: supply the read_clock and move the reg_val_offs back
>
> Signed-off-by: Yintian Tao <yttao@xxxxxxx>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c | 11 ++++------
> drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.h | 1 -
> drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h | 5 +++--
> drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c | 14 +++++-------
> drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c | 14 +++++-------
> drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 28 ++++++++++++------------
> 6 files changed, 33 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> index ea576b4260a4..4e1c0239e561 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
> @@ -304,10 +304,6 @@ int amdgpu_gfx_kiq_init_ring(struct amdgpu_device
> *adev,
>
> spin_lock_init(&kiq->ring_lock);
>
> - r = amdgpu_device_wb_get(adev, &kiq->reg_val_offs);
> - if (r)
> - return r;
> -
> ring->adev = NULL;
> ring->ring_obj = NULL;
> ring->use_doorbell = true;
> @@ -331,7 +327,6 @@ int amdgpu_gfx_kiq_init_ring(struct amdgpu_device
> *adev,
>
> void amdgpu_gfx_kiq_free_ring(struct amdgpu_ring *ring) {
> - amdgpu_device_wb_free(ring->adev, ring->adev->gfx.kiq.reg_val_offs);
> amdgpu_ring_fini(ring);
> }
>
> @@ -675,12 +670,14 @@ uint32_t amdgpu_kiq_rreg(struct amdgpu_device *adev, uint32_t reg)
> uint32_t seq;
> struct amdgpu_kiq *kiq = &adev->gfx.kiq;
> struct amdgpu_ring *ring = &kiq->ring;
> + uint64_t reg_val_offs = 0;
>
> BUG_ON(!ring->funcs->emit_rreg);
>
> spin_lock_irqsave(&kiq->ring_lock, flags);
> amdgpu_ring_alloc(ring, 32);
> - amdgpu_ring_emit_rreg(ring, reg);
> + reg_val_offs = (ring->wptr & ring->buf_mask) + 30;
I think that should be (ring->wptr + 30) & ring->buf_mask. Otherwise the reg_val_offset can be past the end of the ring.
But that still leaves a problem if another command is submitted to the KIQ before you read the returned reg_val from the ring. Your reg_val can be overwritten by the new command and you get the wrong result. Or the command can be overwritten with the reg_val, which will most likely hang the CP.
You could allocate space on the KIQ ring with a NOP command to prevent that space from being overwritten by other commands.
Regards,
Felix
> + amdgpu_ring_emit_rreg(ring, reg, reg_val_offs);
> amdgpu_fence_emit_polling(ring, &seq);
> amdgpu_ring_commit(ring);
> spin_unlock_irqrestore(&kiq->ring_lock, flags); @@ -707,7 +704,7 @@
> uint32_t amdgpu_kiq_rreg(struct amdgpu_device *adev, uint32_t reg)
> if (cnt > MAX_KIQ_REG_TRY)
> goto failed_kiq_read;
>
> - return adev->wb.wb[kiq->reg_val_offs];
> + return ring->ring[reg_val_offs];
>
> failed_kiq_read:
> pr_err("failed to read reg:%x\n", reg); diff --git
> a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.h
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.h
> index 634746829024..ee698f0246d8 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.h
> @@ -103,7 +103,6 @@ struct amdgpu_kiq {
> struct amdgpu_ring ring;
> struct amdgpu_irq_src irq;
> const struct kiq_pm4_funcs *pmf;
> - uint32_t reg_val_offs;
> };
>
> /*
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> index f61664ee4940..a3d88f2aa9f4 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> @@ -181,7 +181,8 @@ struct amdgpu_ring_funcs {
> void (*end_use)(struct amdgpu_ring *ring);
> void (*emit_switch_buffer) (struct amdgpu_ring *ring);
> void (*emit_cntxcntl) (struct amdgpu_ring *ring, uint32_t flags);
> - void (*emit_rreg)(struct amdgpu_ring *ring, uint32_t reg);
> + void (*emit_rreg)(struct amdgpu_ring *ring, uint32_t reg,
> + uint64_t reg_val_offs);
> void (*emit_wreg)(struct amdgpu_ring *ring, uint32_t reg, uint32_t val);
> void (*emit_reg_wait)(struct amdgpu_ring *ring, uint32_t reg,
> uint32_t val, uint32_t mask); @@ -265,7 +266,7 @@ struct
> amdgpu_ring { #define amdgpu_ring_emit_hdp_flush(r)
> (r)->funcs->emit_hdp_flush((r)) #define
> amdgpu_ring_emit_switch_buffer(r) (r)->funcs->emit_switch_buffer((r))
> #define amdgpu_ring_emit_cntxcntl(r, d)
> (r)->funcs->emit_cntxcntl((r), (d)) -#define amdgpu_ring_emit_rreg(r,
> d) (r)->funcs->emit_rreg((r), (d))
> +#define amdgpu_ring_emit_rreg(r, d, o) (r)->funcs->emit_rreg((r),
> +(d), (o))
> #define amdgpu_ring_emit_wreg(r, d, v) (r)->funcs->emit_wreg((r),
> (d), (v)) #define amdgpu_ring_emit_reg_wait(r, d, v, m)
> (r)->funcs->emit_reg_wait((r), (d), (v), (m)) #define
> amdgpu_ring_emit_reg_write_reg_wait(r, d0, d1, v, m)
> (r)->funcs->emit_reg_write_reg_wait((r), (d0), (d1), (v), (m)) diff
> --git a/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
> b/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
> index 0a03e2ad5d95..7c9a5e440509 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
> @@ -7594,21 +7594,19 @@ static void gfx_v10_0_ring_emit_frame_cntl(struct amdgpu_ring *ring, bool start,
> amdgpu_ring_write(ring, v | FRAME_CMD(start ? 0 : 1)); }
>
> -static void gfx_v10_0_ring_emit_rreg(struct amdgpu_ring *ring,
> uint32_t reg)
> +static void gfx_v10_0_ring_emit_rreg(struct amdgpu_ring *ring, uint32_t reg,
> + uint64_t reg_val_offs)
> {
> - struct amdgpu_device *adev = ring->adev;
> - struct amdgpu_kiq *kiq = &adev->gfx.kiq;
> -
> amdgpu_ring_write(ring, PACKET3(PACKET3_COPY_DATA, 4));
> amdgpu_ring_write(ring, 0 | /* src: register*/
> (5 << 8) | /* dst: memory */
> (1 << 20)); /* write confirm */
> amdgpu_ring_write(ring, reg);
> amdgpu_ring_write(ring, 0);
> - amdgpu_ring_write(ring, lower_32_bits(adev->wb.gpu_addr +
> - kiq->reg_val_offs * 4));
> - amdgpu_ring_write(ring, upper_32_bits(adev->wb.gpu_addr +
> - kiq->reg_val_offs * 4));
> + amdgpu_ring_write(ring, lower_32_bits(ring->gpu_addr +
> + reg_val_offs * 4));
> + amdgpu_ring_write(ring, upper_32_bits(ring->gpu_addr +
> + reg_val_offs * 4));
> }
>
> static void gfx_v10_0_ring_emit_wreg(struct amdgpu_ring *ring,
> uint32_t reg, diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
> b/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
> index fc6c2f2bc76c..8e7eee7838e0 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c
> @@ -6383,21 +6383,19 @@ static void gfx_v8_0_ring_emit_patch_cond_exec(struct amdgpu_ring *ring, unsigne
> ring->ring[offset] = (ring->ring_size >> 2) - offset + cur; }
>
> -static void gfx_v8_0_ring_emit_rreg(struct amdgpu_ring *ring,
> uint32_t reg)
> +static void gfx_v8_0_ring_emit_rreg(struct amdgpu_ring *ring, uint32_t reg,
> + uint64_t reg_val_offs)
> {
> - struct amdgpu_device *adev = ring->adev;
> - struct amdgpu_kiq *kiq = &adev->gfx.kiq;
> -
> amdgpu_ring_write(ring, PACKET3(PACKET3_COPY_DATA, 4));
> amdgpu_ring_write(ring, 0 | /* src: register*/
> (5 << 8) | /* dst: memory */
> (1 << 20)); /* write confirm */
> amdgpu_ring_write(ring, reg);
> amdgpu_ring_write(ring, 0);
> - amdgpu_ring_write(ring, lower_32_bits(adev->wb.gpu_addr +
> - kiq->reg_val_offs * 4));
> - amdgpu_ring_write(ring, upper_32_bits(adev->wb.gpu_addr +
> - kiq->reg_val_offs * 4));
> + amdgpu_ring_write(ring, lower_32_bits(ring->gpu_addr +
> + reg_val_offs * 4));
> + amdgpu_ring_write(ring, upper_32_bits(ring->gpu_addr +
> + reg_val_offs * 4));
> }
>
> static void gfx_v8_0_ring_emit_wreg(struct amdgpu_ring *ring,
> uint32_t reg, diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> index 84fcf842316d..ff279b1f5c24 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> @@ -4046,11 +4046,13 @@ static uint64_t gfx_v9_0_kiq_read_clock(struct amdgpu_device *adev)
> uint32_t seq;
> struct amdgpu_kiq *kiq = &adev->gfx.kiq;
> struct amdgpu_ring *ring = &kiq->ring;
> + uint64_t reg_val_offs = 0;
>
> BUG_ON(!ring->funcs->emit_rreg);
>
> spin_lock_irqsave(&kiq->ring_lock, flags);
> amdgpu_ring_alloc(ring, 32);
> + reg_val_offs = (ring->wptr & ring->buf_mask) + 30;
> amdgpu_ring_write(ring, PACKET3(PACKET3_COPY_DATA, 4));
> amdgpu_ring_write(ring, 9 | /* src: register*/
> (5 << 8) | /* dst: memory */
> @@ -4058,10 +4060,10 @@ static uint64_t gfx_v9_0_kiq_read_clock(struct amdgpu_device *adev)
> (1 << 20)); /* write confirm */
> amdgpu_ring_write(ring, 0);
> amdgpu_ring_write(ring, 0);
> - amdgpu_ring_write(ring, lower_32_bits(adev->wb.gpu_addr +
> - kiq->reg_val_offs * 4));
> - amdgpu_ring_write(ring, upper_32_bits(adev->wb.gpu_addr +
> - kiq->reg_val_offs * 4));
> + amdgpu_ring_write(ring, lower_32_bits(ring->gpu_addr +
> + reg_val_offs * 4));
> + amdgpu_ring_write(ring, upper_32_bits(ring->gpu_addr +
> + reg_val_offs * 4));
> amdgpu_fence_emit_polling(ring, &seq);
> amdgpu_ring_commit(ring);
> spin_unlock_irqrestore(&kiq->ring_lock, flags); @@ -4088,8 +4090,8
> @@ static uint64_t gfx_v9_0_kiq_read_clock(struct amdgpu_device *adev)
> if (cnt > MAX_KIQ_REG_TRY)
> goto failed_kiq_read;
>
> - return (uint64_t)adev->wb.wb[kiq->reg_val_offs] |
> - (uint64_t)adev->wb.wb[kiq->reg_val_offs + 1 ] << 32ULL;
> + return (uint64_t)ring->ring[reg_val_offs] |
> + (uint64_t)ring->ring[reg_val_offs + 1 ] << 32ULL;
>
> failed_kiq_read:
> pr_err("failed to read gpu clock\n"); @@ -5482,21 +5484,19 @@ static
> void gfx_v9_0_ring_emit_patch_cond_exec(struct amdgpu_ring *ring, unsigne
> ring->ring[offset] = (ring->ring_size>>2) - offset + cur; }
>
> -static void gfx_v9_0_ring_emit_rreg(struct amdgpu_ring *ring,
> uint32_t reg)
> +static void gfx_v9_0_ring_emit_rreg(struct amdgpu_ring *ring, uint32_t reg,
> + uint64_t reg_val_offs)
> {
> - struct amdgpu_device *adev = ring->adev;
> - struct amdgpu_kiq *kiq = &adev->gfx.kiq;
> -
> amdgpu_ring_write(ring, PACKET3(PACKET3_COPY_DATA, 4));
> amdgpu_ring_write(ring, 0 | /* src: register*/
> (5 << 8) | /* dst: memory */
> (1 << 20)); /* write confirm */
> amdgpu_ring_write(ring, reg);
> amdgpu_ring_write(ring, 0);
> - amdgpu_ring_write(ring, lower_32_bits(adev->wb.gpu_addr +
> - kiq->reg_val_offs * 4));
> - amdgpu_ring_write(ring, upper_32_bits(adev->wb.gpu_addr +
> - kiq->reg_val_offs * 4));
> + amdgpu_ring_write(ring, lower_32_bits(ring->gpu_addr +
> + reg_val_offs * 4));
> + amdgpu_ring_write(ring, upper_32_bits(ring->gpu_addr +
> + reg_val_offs * 4));
> }
>
> static void gfx_v9_0_ring_emit_wreg(struct amdgpu_ring *ring,
> uint32_t reg,
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