> >> If you want to share an updated megaraid sas driver patch based on > >> that, then that's fine. I can incorporate that change in the patch > >> where we add host_tagset to the scsi host template. > > If you share git repo link of next submission, I can send you > > megaraid_sas driver patch which you can include in series. > > So this is my work-en-progress branch: > > https://github.com/hisilicon/kernel-dev/commits/private-topic-blk-mq- > shared-tags-rfc-v8 I tested this repo + megaraid_sas shared hosttag driver. This repo (5.8-rc) has CPU hotplug patch. " bf0beec0607d blk-mq: drain I/O when all CPUs in a hctx are offline" Looking at description of above patch and changes, it looks like megaraid_sas driver can still work without shared host tag for this feature. I observe CPU hotplug works irrespective of shared host tag in megaraid_sas on 5.8-rc. Without shared host tag, megaraid driver will expose single hctx and all the CPU will be mapped to hctx0. Any CPU offline event will have " blk_mq_hctx_notify_offline" callback in blk-mq module. If we do not have this callback/patch, we will see IO timeout. blk_mq_hctx_notify_offline callback will make sure all the outstanding on hctx0 is cleared and only after it is cleared, CPU will go offline. megaraid_sas driver has internal reply_queue mapping which helps to get IO completion on same cpu. Driver get msix index from that table based on " raw_smp_processor_id". If table is mapped correctly at probe time, It is not possible to pick entry of offline CPU. Am I missing anything ? If you can help me to understand why we need shared host tag for CPU hotplug, I can try to frame some test case for possible reproduction. > > I just updated to include the change to have Scsi_Host.host_tagset in > 4291f617a02b commit ("scsi: Add host and host template flag > 'host_tagset'") > > megaraid sas support is not on the branch yet, but I think everything else > required is. And it is mutable, so I'd clone it now if I were you - or > just replace > the required patch onto your v7 branch. I am working on this. > > Thanks, > John
