linux-kernel - Re: [PATCH v3 06/27] ocxl: Tally up the LPC memory on a link & allow it to be mapped

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Date:   Mon, 24 Feb 2020 16:25:18 +1100
From:   Andrew Donnellan <ajd@...ux.ibm.com>
To:     "Alastair D'Silva" <alastair@....ibm.com>, alastair@...ilva.org
Cc:     "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        "Oliver O'Halloran" <oohall@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>,
        Anton Blanchard <anton@...abs.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Cédric Le Goater <clg@...d.org>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kurz <groug@...d.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 06/27] ocxl: Tally up the LPC memory on a link & allow
 it to be mapped

On 21/2/20 2:26 pm, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@...ilva.org>
> 
> Tally up the LPC memory on an OpenCAPI link & allow it to be mapped
> 
> Signed-off-by: Alastair D'Silva <alastair@...ilva.org>

This commit message is a bit short and could do with some further 
explanation.

In particular - it's worth explaining why the tracking of available LPC 
memory needs to be done at a link level, because a single OpenCAPI card 
can have multiple PCI functions, each with multiple AFUs which define an 
amount of LPC memory they have, even if the common case is expected to 
be a single function with a single AFU and thus one LPC area per link.

Snowpatch has a few checkpatch issues to report:

https://openpower.xyz/job/snowpatch/job/snowpatch-linux-checkpatch/11800//artifact/linux/checkpatch.log

The code generally looks okay to me.

> diff --git a/drivers/misc/ocxl/ocxl_internal.h b/drivers/misc/ocxl/ocxl_internal.h
> index 198e4e4bc51d..d0c8c4838f42 100644
> --- a/drivers/misc/ocxl/ocxl_internal.h
> +++ b/drivers/misc/ocxl/ocxl_internal.h
> @@ -142,4 +142,37 @@ int ocxl_irq_offset_to_id(struct ocxl_context *ctx, u64 offset);
>   u64 ocxl_irq_id_to_offset(struct ocxl_context *ctx, int irq_id);
>   void ocxl_afu_irq_free_all(struct ocxl_context *ctx);
>   
> +/**
> + * ocxl_link_add_lpc_mem() - Increment the amount of memory required by an OpenCAPI link
> + *
> + * @link_handle: The OpenCAPI link handle
> + * @offset: The offset of the memory to add
> + * @size: The amount of memory to increment by
> + *
> + * Returns 0 on success, negative on overflow
> + */

I think "amount of memory required" isn't the best way to express this.

Might as well explicitly say -EINVAL on overflow.

-- 
Andrew Donnellan              OzLabs, ADL Canberra
ajd@...ux.ibm.com             IBM Australia Limited