Re: [PATCH v2] vfio: allow secondary process to query IOMMU type

[Thomas Monjalon <thomas@monjalon.net>]

21/01/2019 11:13, Burakov, Anatoly:
> On 19-Jan-19 3:23 AM, Wang, Xiao W wrote:
> > Hi Anatoly,
> > 
> > From: Burakov, Anatoly
> >>
> >> It is only possible to know IOMMU type of a given VFIO container
> >> by attempting to initialize it. Since secondary process never
> >> attempts to set up VFIO container itself (because they're shared
> >> between primary and secondary), it never knows which IOMMU type
> >> the container is using, and never sets up the appropriate config
> >> structures. This results in inability to perform DMA mappings in
> >> secondary process.
> >>
> >> Fix this by allowing secondary process to query IOMMU type of
> >> primary's default container at device initialization.
> >>
> >> Note that this fix is assuming we're only interested in default
> >> container.
> >>
> >> Bugzilla ID: 174
> >>
> >> Fixes: 6bcb7c95fe14 ("vfio: share default container in multi-process")
> >> Cc: dariusz.stojaczyk@intel.com
> >> Cc: stable@dpdk.org
> >>
> >> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
> >> ---
> >>
> >> Notes:
> >>      v2:
> >>      - Check if we found our IOMMU type within list of IOMMU types
> >>      - Don't request new default container fd as this should have
> >>        been done during rte_vfio_enable()
> >>
> >>   lib/librte_eal/linuxapp/eal/eal_vfio.c        | 88 +++++++++++++++++++
> >>   lib/librte_eal/linuxapp/eal/eal_vfio.h        | 12 ++-
> >>   .../linuxapp/eal/eal_vfio_mp_sync.c           | 16 ++++
> >>   3 files changed, 115 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/lib/librte_eal/linuxapp/eal/eal_vfio.c
> >> b/lib/librte_eal/linuxapp/eal/eal_vfio.c
> >> index 72cc65151..c821e8382 100644
> >> --- a/lib/librte_eal/linuxapp/eal/eal_vfio.c
> >> +++ b/lib/librte_eal/linuxapp/eal/eal_vfio.c
> >> @@ -549,6 +549,65 @@ vfio_mem_event_callback(enum rte_mem_event
> >> type, const void *addr, size_t len,
> >>   	}
> >>   }
> >>
> >> +static int
> >> +vfio_sync_default_container(void)
> >> +{
> >> +	struct rte_mp_msg mp_req, *mp_rep;
> >> +	struct rte_mp_reply mp_reply;
> >> +	struct timespec ts = {.tv_sec = 5, .tv_nsec = 0};
> >> +	struct vfio_mp_param *p = (struct vfio_mp_param *)mp_req.param;
> >> +	int iommu_type_id;
> >> +	unsigned int i;
> >> +
> >> +	/* cannot be called from primary */
> >> +	if (rte_eal_process_type() != RTE_PROC_SECONDARY)
> >> +		return -1;
> >> +
> >> +	/* default container fd should have been opened in rte_vfio_enable()
> >> */
> >> +	if (!default_vfio_cfg->vfio_enabled ||
> >> +			default_vfio_cfg->vfio_container_fd < 0) {
> >> +		RTE_LOG(ERR, EAL, "VFIO support is not initialized\n");
> >> +		return -1;
> >> +	}
> >> +
> >> +	/* find default container's IOMMU type */
> >> +	p->req = SOCKET_REQ_IOMMU_TYPE;
> > 
> > Since this function is to sync IOMMU type for the default container, should we make the req type as
> > SOCKET_REQ_DEFAULT_IOMMU_TYPE?
> 
> Hi,
> 
> Sure, that can be done. However, i don't think it warrants a respin 
> unless there's more important stuff to fix also. This patch is a 
> stop-gap, and this stuff will be rewritten for 19.05, so getting this 
> right is not that important :).

Anatoly,
I don't understand what is the use case.
It does not look critical enough to be merged late in 19.02.