[nvmewin] Driver provided alignment for RMW?

Freyensee, James P james.p.freyensee at intel.com
Mon Jun 25 16:38:02 PDT 2012

Thanks for this.

Yes, we'd be interested in 4K debug code for HW bring-ups as well.  If there is a bug in the HW 1st gen, then we can still have SW provide the boundry.

From: Luse, Paul E
Sent: Monday, June 25, 2012 4:35 PM
To: Freyensee, James P; nvmewin at lists.openfabrics.org
Subject: RE: Driver provided alignment for RMW?

If you look at the defines for DBL_BUFFER (or in the patch I just sent DUMB_DRIVER) you'll see debug code for 4K alignments.   I say debug because it does so via double buffering (copying data in/out of our own 4K aligned buffers) because storport will only allow you to specify up to double dword alignment in the config structure you return from findAdapter (element name is AlignmentMask).  I added the 4K debug code because the initial implementation of the software emulator that we used only supported 4K aligned transfers and kept it in there to help with HW bring-ups where this seemed like a common restriction.  For production, you'd want to ask Mssft about changing what alignments a storport miniport can request.

From: nvmewin-bounces at lists.openfabrics.org<mailto:nvmewin-bounces at lists.openfabrics.org> [mailto:nvmewin-bounces at lists.openfabrics.org]<mailto:[mailto:nvmewin-bounces at lists.openfabrics.org]> On Behalf Of Freyensee, James P
Sent: Monday, June 25, 2012 4:30 PM
To: nvmewin at lists.openfabrics.org<mailto:nvmewin at lists.openfabrics.org>
Subject: [nvmewin] Driver provided alignment for RMW?


Could I ask a 'what if'/brainstorming question?  Does the nvme driver provide some type of data alignment on Read-Modify-Writes? Could the driver enforce 4K alignments?  Where would I look/modify in the code?

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