On Sun, Jul 28, 2019 at 02:28:18PM +0300, Oded Gabbay wrote:
> This patch removes the limitation of a single process that can open the
> device.
>
> Now, there is no limitation on the number of processes that can open the
> device and have a valid FD.
>
> However, only a single process can perform compute operations. This is
> enforced by allowing only a single process to have a compute context.
>
> Signed-off-by: Oded Gabbay <oded.gab...@gmail.com>
> ---
> drivers/misc/habanalabs/context.c | 100 +++++++++++++++------
> drivers/misc/habanalabs/device.c | 18 ++--
> drivers/misc/habanalabs/habanalabs.h | 1 -
> drivers/misc/habanalabs/habanalabs_drv.c | 8 --
> drivers/misc/habanalabs/habanalabs_ioctl.c | 7 +-
> 5 files changed, 85 insertions(+), 49 deletions(-)
>
> diff --git a/drivers/misc/habanalabs/context.c
> b/drivers/misc/habanalabs/context.c
> index 57bbe59da9b6..f64220fc3a55 100644
> --- a/drivers/misc/habanalabs/context.c
> +++ b/drivers/misc/habanalabs/context.c
> @@ -56,7 +56,7 @@ void hl_ctx_do_release(struct kref *ref)
> kfree(ctx);
> }
>
> -int hl_ctx_create(struct hl_device *hdev, struct hl_fpriv *hpriv)
> +static int hl_ctx_create(struct hl_device *hdev, struct hl_fpriv *hpriv)
> {
> struct hl_ctx_mgr *mgr = &hpriv->ctx_mgr;
> struct hl_ctx *ctx;
> @@ -89,9 +89,6 @@ int hl_ctx_create(struct hl_device *hdev, struct hl_fpriv
> *hpriv)
> /* TODO: remove for multiple contexts per process */
> hpriv->ctx = ctx;
>
> - /* TODO: remove the following line for multiple process support */
> - hdev->compute_ctx = ctx;
> -
> return 0;
>
> remove_from_idr:
> @@ -206,13 +203,22 @@ bool hl_ctx_is_valid(struct hl_fpriv *hpriv, bool
> requires_compute_ctx)
> int rc;
>
> /* First thing, to minimize latency impact, check if context exists.
> - * Also check if it matches the requirements. If so, exit immediately
> + * This is relevant for the "steady state", where a process context
> + * already exists, and we want to minimize the latency in command
> + * submissions. In that case, we want to see if we can quickly exit
> + * with a valid answer.
> + *
> + * If a context doesn't exists, we must grab the mutex. Otherwise,
> + * there can be nasty races in case of multi-threaded application.
> + *
> + * So, if the context exists and we don't need a compute context,
> + * that's fine. If it exists and the context we have is the compute
> + * context, that's also fine. Other then that, we can't check anything
> + * without the mutex.
> */
> - if (hpriv->ctx) {
> - if ((requires_compute_ctx) && (hdev->compute_ctx != hpriv->ctx))
> - return false;
> + if ((hpriv->ctx) && ((!requires_compute_ctx) ||
> + (hdev->compute_ctx == hpriv->ctx)))
> return true;
> - }
>
> mutex_lock(&hdev->lazy_ctx_creation_lock);
>
> @@ -222,35 +228,73 @@ bool hl_ctx_is_valid(struct hl_fpriv *hpriv, bool
> requires_compute_ctx)
> * creation of a context
> */
> if (hpriv->ctx) {
> - if ((requires_compute_ctx) && (hdev->compute_ctx != hpriv->ctx))
> + if ((!requires_compute_ctx) ||
> + (hdev->compute_ctx == hpriv->ctx))
> + goto unlock_mutex;
> +
> + if (hdev->compute_ctx) {
> valid = false;
> - goto unlock_mutex;
> - }
> + goto unlock_mutex;
> + }
>
> - /* If we already have a compute context, there is no point
> - * of creating one in case we are called from ioctl that needs
> - * a compute context
> - */
> - if ((hdev->compute_ctx) && (requires_compute_ctx)) {
> + /* If we reached here, it means we have a non-compute context,
> + * but there is no compute context on the device. Therefore,
> + * we can try to "upgrade" the existing context to a compute
> + * context
> + */
> + dev_dbg_ratelimited(hdev->dev,
> + "Non-compute context %d exists\n",
> + hpriv->ctx->asid);
> +
> + } else if ((hdev->compute_ctx) && (requires_compute_ctx)) {
> +
> + /* If we already have a compute context in the device, there is
> + * no point of creating one in case we are called from ioctl
> + * that needs a compute context
> + */
> dev_err(hdev->dev,
> "Can't create new compute context as one already
> exists\n");
> valid = false;
> goto unlock_mutex;
> - }
> + } else {
> + /* If we reached here it is because there isn't a context for
> + * the process AND there is no compute context or compute
> + * context wasn't required. In any case, must create a context
> + * for the process
> + */
>
> - rc = hl_ctx_create(hdev, hpriv);
> - if (rc) {
> - dev_err(hdev->dev, "Failed to create context %d\n", rc);
> - valid = false;
> - goto unlock_mutex;
> + rc = hl_ctx_create(hdev, hpriv);
> + if (rc) {
> + dev_err(hdev->dev, "Failed to create context %d\n", rc);
> + valid = false;
> + goto unlock_mutex;
> + }
> +
> + dev_dbg_ratelimited(hdev->dev, "Created context %d\n",
> + hpriv->ctx->asid);
> }
>
> - /* Device is IDLE at this point so it is legal to change PLLs.
> - * There is no need to check anything because if the PLL is
> - * already HIGH, the set function will return without doing
> - * anything
> + /* If we reached here then either we have a new context, or we can
> + * upgrade a non-compute context to a compute context. Do the upgrade
> + * only if the caller required a compute context
> */
> - hl_device_set_frequency(hdev, PLL_HIGH);
> + if (requires_compute_ctx) {
> + WARN(hdev->compute_ctx,
> + "Compute context exists but driver is setting a new
> one");
This will trigger syzbot and will reboot machines that have
'panic-on-warn' set (i.e. all cloud systems). So be _VERY_ careful
about this.
If a user can trigger this, do not use WARN(), that's not what it is
for.
thanks,
greg k-h
