Re: [PATCH] KVM: x86: Allow suppressing prints on RDMSR/WRMSR of unhandled MSRs

["Radim Krčmář" <rkrcmar@redhat.com>]

2017-11-09 19:30+0100, Paolo Bonzini:
> On 09/11/2017 16:22, Radim Krčmář wrote:
> > 2017-11-08 14:32+0200, Eyal Moscovici:
> >> Some guests use these unhandled MSRs very frequently.
> >> This cause dmesg to be populated with lots of aggregated messages on
> >> usage of ignored MSRs. As ignore_msrs=true means that the user is
> >> well-aware his guest use ignored MSRs, allow to also disable the
> >> prints on their usage.
> >>
> >> An example of such guest is ESXi which tends to access a lot to MSR
> >> 0x34 (MSR_SMI_COUNT) very frequently.
> >>
> >> In addition, we have observed this to cause unnecessary delays to
> >> guest execution. Such an example is ESXi which experience networking
> >> delays in it's guests (L2 guests) because of these prints (even when
> >> prints are rate-limited). This can easily be reproduced by pinging
> >> from one L2 guest to another.  Once in a while, a peak in ping RTT
> >> will be observed. Removing these unhandled MSR prints solves the
> >> issue.
> >>
> >> Because these prints can help diagnose issues with guests,
> >> this commit only suppress them by a module parameter instead of
> >> removing them from code entirely.
> >>
> >> Signed-off-by: Eyal Moscovici <eyal.moscovici@oracle.com>
> >> Reviewed-by: Liran Alon <liran.alon@oracle.com>
> >> Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> >> Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> >> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> >> ---
> >>  arch/x86/kvm/x86.c | 17 +++++++++++++----
> >>  1 file changed, 13 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> >> index 03869eb..21c0059 100644
> >> --- a/arch/x86/kvm/x86.c
> >> +++ b/arch/x86/kvm/x86.c
> >> @@ -107,6 +107,9 @@
> >>  static bool __read_mostly ignore_msrs = 0;
> >>  module_param(ignore_msrs, bool, S_IRUGO | S_IWUSR);
> >>  
> >> +static bool __read_mostly suppress_ignore_msrs_prints = false;
> >> +module_param(suppress_ignore_msrs_prints, bool, S_IRUGO | S_IWUSR);
> > 
> > What about calling it 'print_ignored_msrs' and default to true?
> 
> Makes sense! s/print/report/ perhaps?

s/suppress_ignore_msrs_prints/report_ignored_msrs/ and applied, thanks.