linux-kernel - Re: [PATCH v5 5/7] ocxl: Expose the thread

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Date:   Thu, 31 May 2018 14:42:28 +1000
From:   Andrew Donnellan <andrew.donnellan@....ibm.com>
To:     "Alastair D'Silva" <alastair@....ibm.com>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        mikey@...ling.org, vaibhav@...ux.vnet.ibm.com,
        aneesh.kumar@...ux.vnet.ibm.com, malat@...ian.org,
        felix@...ux.vnet.ibm.com, pombredanne@...b.com,
        sukadev@...ux.vnet.ibm.com, npiggin@...il.com,
        gregkh@...uxfoundation.org, arnd@...db.de,
        fbarrat@...ux.vnet.ibm.com, corbet@....net,
        "Alastair D'Silva" <alastair@...ilva.org>
Subject: Re: [PATCH v5 5/7] ocxl: Expose the thread_id needed for wait on
 POWER9

On 11/05/18 16:13, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@...ilva.org>
> 
> In order to successfully issue as_notify, an AFU needs to know the TID
> to notify, which in turn means that this information should be
> available in userspace so it can be communicated to the AFU.
> 
> Signed-off-by: Alastair D'Silva <alastair@...ilva.org>

Acked-by: Andrew Donnellan <andrew.donnellan@....ibm.com>

Comments below.

> +#ifdef CONFIG_PPC64
> +static long afu_ioctl_enable_p9_wait(struct ocxl_context *ctx,
> +		struct ocxl_ioctl_p9_wait __user *uarg)
> +{
> +	struct ocxl_ioctl_p9_wait arg;
> +
> +	memset(&arg, 0, sizeof(arg));
> +
> +	if (cpu_has_feature(CPU_FTR_P9_TIDR)) {
> +		enum ocxl_context_status status;
> +
> +		// Locks both status & tidr
> +		mutex_lock(&ctx->status_mutex);
> +		if (!ctx->tidr) {
> +			if (set_thread_tidr(current))
> +				return -ENOENT;
> +
> +			ctx->tidr = current->thread.tidr;
> +		}
> +
> +		status = ctx->status;
> +		mutex_unlock(&ctx->status_mutex);
> +
> +		if (status == ATTACHED) {
> +			int rc;
> +			struct link *link = ctx->afu->fn->link;
> +
> +			rc = ocxl_link_update_pe(link, ctx->pasid, ctx->tidr);
> +			if (rc)
> +				return rc;
> +		}
> +
> +		arg.thread_id = ctx->tidr;
> +	} else
> +		return -ENOENT;

I didn't pick this up before - please please please use braces on both 
sides of the if here.

> +
> +	if (copy_to_user(uarg, &arg, sizeof(arg)))
> +		return -EFAULT;
> +
> +	return 0;
> +}
> +#endif

> diff --git a/include/misc/ocxl.h b/include/misc/ocxl.h
> index 51ccf76db293..9ff6ddc28e22 100644
> --- a/include/misc/ocxl.h
> +++ b/include/misc/ocxl.h
> @@ -188,6 +188,15 @@ extern int ocxl_link_add_pe(void *link_handle, int pasid, u32 pidr, u32 tidr,
>   		void (*xsl_err_cb)(void *data, u64 addr, u64 dsisr),
>   		void *xsl_err_data);
>   
> +/**
> + * Update values within a Process Element
> + *
> + * link_handle: the link handle associated with the process element
> + * pasid: the PASID for the AFU context
> + * tid: the new thread id for the process element
> + */
> +extern int ocxl_link_update_pe(void *link_handle, int pasid, __u16 tid);

My earlier comment about __u16 vs u16 applies for this declaration (and 
the body declaration) as well

-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan@....ibm.com  IBM Australia Limited