Re: [PATCH 0/2] Notify NVME HW when system reset happens

["Ni, Ruiyu" <ruiyu.ni@intel.com>]

The NVME controller requires notification for shutdown as part of its management of internal structures.  Even with FUA, failing to notify the NVME controller to shutdown power off causes the NVME controller to take quite some time to organize its tables on the next power on.  This time exceeds the normal timeout, so we would fail to boot the NVME disk. 

I will put above explanation into the commit message as well.

Thanks/Ray

> -----Original Message-----
> From: Wu, Hao A
> Sent: Monday, August 7, 2017 3:14 PM
> To: Ni, Ruiyu <ruiyu.ni@intel.com>; edk2-devel@lists.01.org
> Subject: RE: [edk2] [PATCH 0/2] Notify NVME HW when system reset
> happens
> 
> Hi Ray,
> 
> Just for curiosity, I checked the NVME spec for the purpose of a shutdown
> notification to the controller when there is a power-off for the device. And
> found the following:
> 
> 1. Will increase the field 'Unsafe Shutdowns' in the SMART/Health
> Information data (Section 5.10.1.2).
> 
> 2. Subsequent reads for locations written to the volatile write cache that
> were not written to non-volatile storage may return older data. (Section
> 6.4.2.1)
> 
> For 2, the implementation of the NVME driver always sets the Force Unit
> Access (FUA) bit for write operations. Hence, the read operation will reflect
> the latest data on device.
> 
> So missing the shutdown notification will increase the number of 'Unsafe
> Shutdowns' tracked by the controller. Is there any other issue being
> introduced by missing the notification?
> 
> Besides, the change is good for me.
> 
> 
> Best Regards,
> Hao Wu
> 
> > -----Original Message-----
> > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> > Ruiyu Ni
> > Sent: Monday, August 07, 2017 11:32 AM
> > To: edk2-devel@lists.01.org
> > Subject: [edk2] [PATCH 0/2] Notify NVME HW when system reset happens
> >
> > Per NVM Express Spec, software should notify NVME HW when shutdown
> > occurs.
> >
> > The host should set the Shutdown Notification (CC.SHN) field to 01b to
> > indicate a normal shutdown operation. The controller indicates when
> > shutdown processing is completed by updating the Shutdown Status
> > (CSTS.SHST) field to 10b.
> >
> > Ruiyu Ni (2):
> >   MdePkg/Nvme: Add NVME shutdown notification related macros
> >   MdeModulePkg/NvmExpressDxe: Notify NVME HW when system reset
> happens
> >
> >  MdeModulePkg/Bus/Pci/NvmExpressDxe/NvmExpress.c    |   7 +-
> >  MdeModulePkg/Bus/Pci/NvmExpressDxe/NvmExpress.h    |  23 ++-
> >  .../Bus/Pci/NvmExpressDxe/NvmExpressDxe.inf        |   3 +-
> >  MdeModulePkg/Bus/Pci/NvmExpressDxe/NvmExpressHci.c | 181
> > ++++++++++++++++++++-
> >  MdePkg/Include/IndustryStandard/Nvme.h             |   6 +-
> >  5 files changed, 215 insertions(+), 5 deletions(-)
> >
> > --
> > 2.12.2.windows.2
> >
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