On Tue, 2017-07-25 at 07:46 -0700, Dan Williams wrote: > On Tue, Jul 25, 2017 at 7:27 AM, Pankaj Gupta <pagupta@xxxxxxxxxx> > wrote: > > > > Looks like only way to send flush(blk dev) from guest to host with > > nvdimm > > is using flush hint addresses. Is this the correct interface I am > > looking? > > > > blkdev_issue_flush > > submit_bio_wait > > submit_bio > > generic_make_request > > pmem_make_request > > ... > > if (bio->bi_opf & REQ_FLUSH) > > nvdimm_flush(nd_region); > > I would inject a paravirtualized version of pmem_make_request() that > sends an async flush operation over virtio to the host. Don't try to > use flush hint addresses for this, they don't have the proper > semantics. The guest should be allowed to issue the flush and receive > the completion asynchronously rather than taking a vm exist and > blocking on that request. That is my feeling, too. A slower IO device benefits greatly from an asynchronous flush mechanism. -- All rights reversed
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