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From: Thomas Monjalon <thomas@monjalon.net>
To: Shijith Thotton <sthotton@marvell.com>
Cc: dev@dpdk.org, pbhagavatula@marvell.com,
Shijith Thotton <sthotton@marvell.com>, Honnappa.Nagarahalli@arm.com,
bruce.richardson@intel.com, jerinj@marvell.com, mb@smartsharesystems.com,
olivier.matz@6wind.com, stephen@networkplumber.org, david.marchand@redhat.com
Subject: Re: [PATCH v3 2/5] mbuf: add second dynamic field member for VA only
build
Date: Wed, 28 Sep 2022 09:24:51 +0200
Message-ID: <5861713.UjTJXf6HLC@thomas>
In-Reply-To: <cc80e7e37896d5076f6e73f1515558b11dfd7e9c.1663767715.git.sthotton@marvell.com>
References: <20220907134340.3629224-1-sthotton@marvell.com>
<cover.1663767715.git.sthotton@marvell.com>
<cc80e7e37896d5076f6e73f1515558b11dfd7e9c.1663767715.git.sthotton@marvell.com>
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Errors-To: dev-bounces@dpdk.org
21/09/2022 15:56, Shijith Thotton:
> mbuf physical address field is not used in builds which only uses VA. It
> is used to expand the dynamic field area.
>
> Signed-off-by: Shijith Thotton <sthotton@marvell.com>
We cannot condition the use of the dynamic field.
I think it is enough justification to reject this patch.
And about adding a compilation option for IOVA in the first patch of this series,
I think it is not the direction the majority wants DPDK to go.
We tend to avoid compilation options.
> @@ -579,15 +579,23 @@ struct rte_mbuf {
> RTE_MARKER cacheline0;
>
> void *buf_addr; /**< Virtual address of segment buffer. */
> - /**
> - * Physical address of segment buffer.
> - * This field is invalid if the build is configured to use only
> - * virtual address as IOVA (i.e. RTE_IOVA_AS_VA is 1).
> - * Force alignment to 8-bytes, so as to ensure we have the exact
> - * same mbuf cacheline0 layout for 32-bit and 64-bit. This makes
> - * working on vector drivers easier.
> - */
> - rte_iova_t buf_iova __rte_aligned(sizeof(rte_iova_t));
> + RTE_STD_C11
> + union {
> + /**
> + * Physical address of segment buffer.
> + * This field is invalid if the build is configured to use only
> + * virtual address as IOVA (i.e. RTE_IOVA_AS_VA is 1).
> + * Force alignment to 8-bytes, so as to ensure we have the exact
> + * same mbuf cacheline0 layout for 32-bit and 64-bit. This makes
> + * working on vector drivers easier.
> + */
> + rte_iova_t buf_iova __rte_aligned(sizeof(rte_iova_t));
> + /**
> + * Reserved for dynamic field in builds where physical address
> + * field is invalid.
> + */
> + uint64_t dynfield2;
> + };