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Message-ID: <1d109f0f-e866-4f87-b8f9-06595dbc51ff@quicinc.com>
Date: Wed, 16 Apr 2025 23:08:55 +0530
From: Akhil P Oommen <quic_akhilpo@...cinc.com>
To: Rob Clark <robdclark@...il.com>, <dri-devel@...ts.freedesktop.org>
CC: <freedreno@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
"Rob
Clark" <robdclark@...omium.org>, Sean Paul <sean@...rly.run>,
Konrad Dybcio
<konradybcio@...nel.org>,
Abhinav Kumar <quic_abhinavk@...cinc.com>,
"Dmitry
Baryshkov" <lumag@...nel.org>,
Marijn Suijten
<marijn.suijten@...ainline.org>,
David Airlie <airlied@...il.com>, Simona
Vetter <simona@...ll.ch>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 14/34] drm/msm: Lazily create context VM
On 3/19/2025 8:22 PM, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
>
> In the next commit, a way for userspace to opt-in to userspace managed
> VM is added. For this to work, we need to defer creation of the VM
> until it is needed.
>
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
> drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 3 ++-
> drivers/gpu/drm/msm/adreno/adreno_gpu.c | 14 +++++++-----
> drivers/gpu/drm/msm/msm_drv.c | 29 ++++++++++++++++++++-----
> drivers/gpu/drm/msm/msm_gem_submit.c | 2 +-
> drivers/gpu/drm/msm/msm_gpu.h | 9 +++++++-
> 5 files changed, 43 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 4811be5a7c29..0b1e2ba3539e 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -112,6 +112,7 @@ static void a6xx_set_pagetable(struct a6xx_gpu *a6xx_gpu,
> {
> bool sysprof = refcount_read(&a6xx_gpu->base.base.sysprof_active) > 1;
> struct msm_context *ctx = submit->queue->ctx;
> + struct drm_gpuvm *vm = msm_context_vm(submit->dev, ctx);
> struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
> phys_addr_t ttbr;
> u32 asid;
> @@ -120,7 +121,7 @@ static void a6xx_set_pagetable(struct a6xx_gpu *a6xx_gpu,
> if (ctx->seqno == ring->cur_ctx_seqno)
> return;
>
> - if (msm_iommu_pagetable_params(to_msm_vm(ctx->vm)->mmu, &ttbr, &asid))
> + if (msm_iommu_pagetable_params(to_msm_vm(vm)->mmu, &ttbr, &asid))
> return;
>
> if (adreno_gpu->info->family >= ADRENO_7XX_GEN1) {
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> index 0f71703f6ec7..e4d895dda051 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> @@ -351,6 +351,8 @@ int adreno_get_param(struct msm_gpu *gpu, struct msm_context *ctx,
> {
> struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> struct drm_device *drm = gpu->dev;
> + /* Note ctx can be NULL when called from rd_open(): */
> + struct drm_gpuvm *vm = ctx ? msm_context_vm(drm, ctx) : NULL;
>
> /* No pointer params yet */
> if (*len != 0)
> @@ -396,8 +398,8 @@ int adreno_get_param(struct msm_gpu *gpu, struct msm_context *ctx,
> *value = 0;
> return 0;
> case MSM_PARAM_FAULTS:
> - if (ctx->vm)
> - *value = gpu->global_faults + to_msm_vm(ctx->vm)->faults;
> + if (vm)
> + *value = gpu->global_faults + to_msm_vm(vm)->faults;
> else
> *value = gpu->global_faults;
> return 0;
> @@ -405,14 +407,14 @@ int adreno_get_param(struct msm_gpu *gpu, struct msm_context *ctx,
> *value = gpu->suspend_count;
> return 0;
> case MSM_PARAM_VA_START:
> - if (ctx->vm == gpu->vm)
> + if (vm == gpu->vm)
> return UERR(EINVAL, drm, "requires per-process pgtables");
> - *value = ctx->vm->mm_start;
> + *value = vm->mm_start;
> return 0;
> case MSM_PARAM_VA_SIZE:
> - if (ctx->vm == gpu->vm)
> + if (vm == gpu->vm)
> return UERR(EINVAL, drm, "requires per-process pgtables");
> - *value = ctx->vm->mm_range;
> + *value = vm->mm_range;
> return 0;
> case MSM_PARAM_HIGHEST_BANK_BIT:
> *value = adreno_gpu->ubwc_config.highest_bank_bit;
> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> index 6ef29bc48bb0..6fd981ee6aee 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/drivers/gpu/drm/msm/msm_drv.c
> @@ -214,10 +214,29 @@ static void load_gpu(struct drm_device *dev)
> mutex_unlock(&init_lock);
> }
>
> +/**
> + * msm_context_vm - lazily create the context's VM
> + *
> + * @dev: the drm device
> + * @ctx: the context
> + *
> + * The VM is lazily created, so that userspace has a chance to opt-in to having
> + * a userspace managed VM before the VM is created.
> + *
> + * Note that this does not return a reference to the VM. Once the VM is created,
> + * it exists for the lifetime of the context.
> + */
> +struct drm_gpuvm *msm_context_vm(struct drm_device *dev, struct msm_context *ctx)
> +{
> + struct msm_drm_private *priv = dev->dev_private;
> + if (!ctx->vm)
hmm. This is racy and it is in a userspace accessible path!
-Akhil
> + ctx->vm = msm_gpu_create_private_vm(priv->gpu, current);
> + return ctx->vm;
> +}
> +
> static int context_init(struct drm_device *dev, struct drm_file *file)
> {
> static atomic_t ident = ATOMIC_INIT(0);
> - struct msm_drm_private *priv = dev->dev_private;
> struct msm_context *ctx;
>
> ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
> @@ -230,7 +249,6 @@ static int context_init(struct drm_device *dev, struct drm_file *file)
> kref_init(&ctx->ref);
> msm_submitqueue_init(dev, ctx);
>
> - ctx->vm = msm_gpu_create_private_vm(priv->gpu, current);
> file->driver_priv = ctx;
>
> ctx->seqno = atomic_inc_return(&ident);
> @@ -408,7 +426,7 @@ static int msm_ioctl_gem_info_iova(struct drm_device *dev,
> * Don't pin the memory here - just get an address so that userspace can
> * be productive
> */
> - return msm_gem_get_iova(obj, ctx->vm, iova);
> + return msm_gem_get_iova(obj, msm_context_vm(dev, ctx), iova);
> }
>
> static int msm_ioctl_gem_info_set_iova(struct drm_device *dev,
> @@ -417,18 +435,19 @@ static int msm_ioctl_gem_info_set_iova(struct drm_device *dev,
> {
> struct msm_drm_private *priv = dev->dev_private;
> struct msm_context *ctx = file->driver_priv;
> + struct drm_gpuvm *vm = msm_context_vm(dev, ctx);
>
> if (!priv->gpu)
> return -EINVAL;
>
> /* Only supported if per-process address space is supported: */
> - if (priv->gpu->vm == ctx->vm)
> + if (priv->gpu->vm == vm)
> return UERR(EOPNOTSUPP, dev, "requires per-process pgtables");
>
> if (should_fail(&fail_gem_iova, obj->size))
> return -ENOMEM;
>
> - return msm_gem_set_iova(obj, ctx->vm, iova);
> + return msm_gem_set_iova(obj, vm, iova);
> }
>
> static int msm_ioctl_gem_info_set_metadata(struct drm_gem_object *obj,
> diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> index c65f3a6a5256..9731ad7993cf 100644
> --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> @@ -63,7 +63,7 @@ static struct msm_gem_submit *submit_create(struct drm_device *dev,
>
> kref_init(&submit->ref);
> submit->dev = dev;
> - submit->vm = queue->ctx->vm;
> + submit->vm = msm_context_vm(dev, queue->ctx);
> submit->gpu = gpu;
> submit->cmd = (void *)&submit->bos[nr_bos];
> submit->queue = queue;
> diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
> index d8425e6d7f5a..c15aad288552 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.h
> +++ b/drivers/gpu/drm/msm/msm_gpu.h
> @@ -362,7 +362,12 @@ struct msm_context {
> */
> int queueid;
>
> - /** @vm: the per-process GPU address-space */
> + /**
> + * @vm:
> + *
> + * The per-process GPU address-space. Do not access directly, use
> + * msm_context_vm().
> + */
> struct drm_gpuvm *vm;
>
> /** @kref: the reference count */
> @@ -447,6 +452,8 @@ struct msm_context {
> atomic64_t ctx_mem;
> };
>
> +struct drm_gpuvm *msm_context_vm(struct drm_device *dev, struct msm_context *ctx);
> +
> /**
> * msm_gpu_convert_priority - Map userspace priority to ring # and sched priority
> *
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