Re: [edk2-devel][PATCH v2 0/2] Add Volatile Keyword to NvmExpress Passthru CQs

["Wu, Hao A" <hao.a.wu@intel.com>]

Pushed via:
PR - https://github.com/tianocore/edk2/pull/4353
Commits:
https://github.com/tianocore/edk2/commit/293b97d0c4624c13a4e934294d2c4b161a09a91b
https://github.com/tianocore/edk2/commit/8dbf868e02c71b407e31f9b41b5266169c702812

Best Regards,
Hao Wu

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Wu, Hao A
> Sent: Thursday, May 4, 2023 10:20 AM
> To: devel@edk2.groups.io; osde@linux.microsoft.com
> Cc: Ni, Ray <ray.ni@intel.com>; Wang, Jian J <jian.j.wang@intel.com>; Gao,
> Liming <gaoliming@byosoft.com.cn>; Michael Kubacki
> <mikuback@linux.microsoft.com>; Sean Brogan <sean.brogan@microsoft.com>
> Subject: Re: [edk2-devel][PATCH v2 0/2] Add Volatile Keyword to NvmExpress
> Passthru CQs
> 
> For the series:
> Reviewed-by: Hao A Wu <hao.a.wu@intel.com>
> 
> Will wait a couple of days before merging to see if comments from other
> reviewers.
> 
> Best Regards,
> Hao Wu
> 
> > -----Original Message-----
> > From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Oliver
> > Smith-Denny
> > Sent: Friday, April 28, 2023 1:36 AM
> > To: devel@edk2.groups.io
> > Cc: Wu, Hao A <hao.a.wu@intel.com>; Ni, Ray <ray.ni@intel.com>; Wang,
> > Jian J <jian.j.wang@intel.com>; Gao, Liming
> > <gaoliming@byosoft.com.cn>; Michael Kubacki
> > <mikuback@linux.microsoft.com>; Sean Brogan
> > <sean.brogan@microsoft.com>
> > Subject: [edk2-devel][PATCH v2 0/2] Add Volatile Keyword to NvmExpress
> > Passthru CQs
> >
> > NVMe CQs are hardware queues mapped to EFI memory.
> > In the NVMExpress Passthru implementations in PEI and DXE, it has been
> > observed that NVMe CQs are not marked volatile, meaning the compiler
> > has significant leeway to optimize accesses to these structures.
> >
> > This led to an issue where the passthru driver waited for a timeout
> > period for an NVMe CQ to mark that it was finished with a transaction,
> > but the compiler had optimized away the read to the actual HW mapped
> > memory, so the transaction had completed but the timeout continued.
> >
> > Marking the CQs as volatile fixes this issue as the reads happen to
> > the actual HW.
> >
> > Personal GitHub PR: https://github.com/tianocore/edk2/pull/4320
> > Github branch: https://github.com/os-d/edk2/tree/osde/volatile_cq_v2
> >
> > Changes v1 => v2:
> > =================
> > - Remove volatile keyword from SQ
> >
> > Cc: Hao A Wu <hao.a.wu@intel.com>
> > Cc: Ray Ni <ray.ni@intel.com>
> > Cc: Jian J Wang <jian.j.wang@intel.com>
> > Cc: Liming Gao <gaoliming@byosoft.com.cn>
> > Cc: Michael Kubacki <mikuback@linux.microsoft.com>
> > Cc: Sean Brogan <sean.brogan@microsoft.com>
> >
> >
> > Oliver Smith-Denny (2):
> >   Add the volatile keyword to NvmExpressDxe's Passthru CQ
> >   Add volatile keyword to NvmExpressPei's Passthru CQ
> >
> >  MdeModulePkg/Bus/Pci/NvmExpressDxe/NvmExpressPassthru.c    | 6 +++---
> >  MdeModulePkg/Bus/Pci/NvmExpressPei/NvmExpressPeiPassThru.c | 6 +++---
> >  2 files changed, 6 insertions(+), 6 deletions(-)
> >
> > --
> > 2.40.0
> >
> >
> >
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