On 2/18/21 10:57 AM, Jan Beulich wrote: > On 18.02.2021 16:52, Roger Pau Monné wrote: >> On Thu, Feb 18, 2021 at 12:54:13PM +0100, Jan Beulich wrote: >>> On 18.02.2021 11:42, Roger Pau Monné wrote: >>>> Not that you need to implement the full thing now, but maybe we could >>>> have something like: >>>> >>>> " >>>> =item B<ignore_msrs=[ "MSR_RANGE, "MSR_RANGE", ..]> >>>> >>>> Specify a list of MSR ranges that will be ignored by the hypervisor: >>>> reads will return zeros and writes will be discarded without raising a >>>> #GP. >>>> >>>> Each MSR_RANGE is given in hexadecimal format and may be a range, e.g. >>>> c00102f0-c00102f1 (inclusive), or a single MSR, e.g. c00102f1. >>>> " >>>> >>>> Then you can print the messages in the hypervisor using a guest log >>>> level and modify it on demand in order to get more verbose output? >>> "Modify on demand"? Irrespective of what you mean with this, ... >>> >>>> I don't think selecting whether the messages are printed or not from >>>> xl is that helpful as the same could be achieved using guest_loglvl. >>> ... controlling this via guest_loglvl would affect various other >>> log messages' visibility. >> Right, but do we really need this level of per-guest log control, >> implemented in this way exclusively for MSRs?
In a multi-tenant environment we may need to figure out why a particular guest is failing to boot, without affecting behavior of other guests. If we had per-guest log level in general then what you are suggesting would be the right thing to do IMO. Maybe that's what we should add? -boris >> >> We don't have a way for other parts of the code to have such >> fine-grained control about what messages should be printed, and I >> don't think MSR should be an exception. I assume this would be used to >> detect which MSRs a guest is trying to access, and I would be fine >> just using guest_loglvl to that end, the more that it can be modified >> at run time now. > I can certainly see your point. The problem is that for guests > heavily accessing such MSRs, all other messages may disappear > due to rate limiting. That's not going to be helpful.
