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    SubjectRe: [ofa-general] Re: [ewg] Re: [PATCH] IB/ehca: Serialize HCA-related hCalls on POWER5
    Date wrote on 13.12.2007 20:22:49:

    > On Dec 13, 2007 12:30 AM, Or Gerlitz <> wrote:
    > > The current implementation of the open iscsi initiator makes sure to
    > > issue commands in thread (sleepable) context, see iscsi_xmitworker and
    > > references to it in drivers/scsi/libiscsi.c , so this keeps ehca users
    > > safe for the time being.

    > I agree, *some* form of FMR support is important for iSER (and probably
    > for NFS over RDMA as well). Rather than adding a crippled NO FMR
    > mode it would make more sense to add support for FMR Work Requests.
    > I'm not certain what, if any, impact that would have on the Power5
    > but that's certainly a cleaner path for iWARP.

    Well, FMR WRs wouldn't change the eHCA issue -- the driver would have to
    make an hCall in any case, and the architecture says that the hCalls used
    in this scenario might return H_LONG_BUSY, causing the driver to sleep. No
    way around that. Because of this, eHCA's FMRs are actually standard MRs
    with a different API.

    If, as Or said, the iSCSI initiator issues commands in sleepable context
    anyway, nothing would be lost by using standard MRs as a fallback solution
    if FMRs aren't available, would it?


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