Re: [PATCH 0/4] hw/nvme: add support for TP4084

[Klaus Jensen <its@irrelevant.dk>]

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On Jun  8 03:28, Niklas Cassel via wrote:
> Hello there,
> 
> considering that Linux v5.19-rc1 is out which includes support for
> NVMe TP4084:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/nvme/host/core.c?id=354201c53e61e493017b15327294b0c8ab522d69
> 
> I thought that it might be nice to have QEMU support for the same.
> 
> TP4084 adds a new mode, CC.CRIME, that can be used to mark a namespace
> as ready independently from the controller.
> 
> When CC.CRIME is 0 (default), things behave as before, all namespaces
> are ready when CSTS.RDY gets set to 1.
> 
> Add a new "ready_delay" namespace device parameter, in order to emulate
> different ready latencies for namespaces when CC.CRIME is 1.
> 
> The patch series also adds a "crwmt" controller parameter, in order to
> be able to expose the worst case timeout that the host should wait for
> all namespaces to become ready.
> 
> 
> Example qemu cmd line for the new options:
> 
> # delay in s (20s)
> NS1_DELAY_S=20
> # convert to units of 500ms
> NS1_DELAY=$((NS1_DELAY_S*2))
> 
> # delay in s (60s)
> NS2_DELAY_S=60
> # convert to units of 500ms
> NS2_DELAY=$((NS2_DELAY_S*2))
> 
> # timeout in s (120s)
> CRWMT_S=120
> # convert to units of 500ms
> CRWMT=$((CRWMT_S*2))
> 
>              -device nvme,serial=deadbeef,crwmt=$CRWMT \
>              -drive file=$NS1_DATA,id=nvm-1,format=raw,if=none \
>              -device nvme-ns,drive=nvm-1,ready_delay=$NS1_DELAY \
>              -drive file=$NS2_DATA,id=nvm-2,format=raw,if=none \
>              -device nvme-ns,drive=nvm-2,ready_delay=$NS2_DELAY \
> 
> 
> Niklas Cassel (4):
>   hw/nvme: claim NVMe 2.0 compliance
>   hw/nvme: store a pointer to the NvmeSubsystem in the NvmeNamespace
>   hw/nvme: add support for ratified TP4084
>   hw/nvme: add new never_ready parameter to test the DNR bit
> 
>  hw/nvme/ctrl.c       | 151 +++++++++++++++++++++++++++++++++++++++++--
>  hw/nvme/ns.c         |  17 +++++
>  hw/nvme/nvme.h       |   9 +++
>  hw/nvme/trace-events |   1 +
>  include/block/nvme.h |  60 ++++++++++++++++-
>  5 files changed, 233 insertions(+), 5 deletions(-)
> 
> -- 
> 2.36.1
> 
> 

Hi Niklas,

I've been going back and forth on my position on this.

I'm not straight up against it, but this only seems useful as a one-off
patch to test the kernel support for this. Considering the limitations
you state and the limited use case, I fear this is a little bloaty to
carry upstream.

But I totally acknowledge that this is a horrible complicated behavior
to implement on the driver side, so I guess we might all benefit from
this.

Keith, do you have an opinion on this?

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