> -----Original Message----- > From: Greg KH [mailto:g...@kroah.com] > Sent: Friday, January 06, 2017 11:43 PM > To: Long Li <lon...@microsoft.com> > Cc: KY Srinivasan <k...@microsoft.com>; Haiyang Zhang > <haiya...@microsoft.com>; de...@linuxdriverproject.org; linux- > ker...@vger.kernel.org > Subject: Re: [PATCH v2] hv: retry infinitely on hypercall transient failures > > On Sat, Jan 07, 2017 at 07:23:14AM +0000, Long Li wrote: > > > -----Original Message----- > > > From: Greg KH [mailto:g...@kroah.com] > > > Sent: Wednesday, January 04, 2017 11:48 PM > > > To: Long Li <lon...@microsoft.com> > > > Cc: KY Srinivasan <k...@microsoft.com>; Haiyang Zhang > > > <haiya...@microsoft.com>; de...@linuxdriverproject.org; linux- > > > ker...@vger.kernel.org > > > Subject: Re: [PATCH v2] hv: retry infinitely on hypercall transient > > > failures > > > > > > On Wed, Jan 04, 2017 at 06:12:20PM -0800, Long Li wrote: > > > > From: Long Li <lon...@microsoft.com> > > > > > > > > Hyper-v host guarantees that a hypercall will finish in reasonable time. > > > > Retry infinitely on transient failures to avoid returning error to upper > layer. > > > > > > Again, never retry "forever", always have a way out, otherwise you will > crash. > > > > > > And again, why are you making this change? What problem does it solve? > > > > The problem it tries to solve is that in this code we are returning > > error prematurely on transient failures. The hypercall is used mostly > > in channel establishment. If we return a transient failure, the VM may > > not boot or not useful after boot due to some devices missing. > > > > Another approach is to increase the number of retries. But we don't > > know how many retries is safe, and Windows host side expects the guest > > retry infinitely and not return error on transient failures. > > That implies a lot of trust in the host side, don't you think? > > Worse case, make the delay a minute or so, but give the system a way out > incase there's a bug in the host. As there will be bugs in the host, just > like > there are bugs in the client :)
This makes sense. 1 minute is a long time for a hypercall. I will send V3. > > thanks, > > greg k-h
