[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH 1/2] x86/VPMU: Disable VPMU when NMI watchdog is on

On 01/28/2015 05:41 PM, Andrew Cooper wrote:
On 28/01/2015 22:33, Boris Ostrovsky wrote:
On 01/28/2015 04:49 PM, Andrew Cooper wrote:
On 28/01/2015 19:56, Boris Ostrovsky wrote:
NMI watchdog sets APIC_LVTPC register to generate an NMI when PMU
overflow occurs. This may be overwritten by VPMU code later,
turning off the watchdog.

We should disable VPMU when NMI watchdog is running.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

I completely agree with the aim, but this patch is clunky and you have
missed the case where neither 'watchdog' nor 'vpmu' is specified on the
command line, but the booleans have been tweaked (which is the XenServer
way of choosing defaults while keeping the length of the command line

You mean binary patching? Or does XenServer change those flags before
compilation? Yes, I haven't thought about this.

We patch the source before compiling.


How does this enable NMI watchdog? This patch sets watchdog_force but that alone doesn't enable anything. Or are there other changes that set opt_watchdog (which I was going to test as you suggested below).


A more simple approach, which doesn't involve exposing opt_vpmu_enabled
or changing any nmi code, would be to have a check in vpmu_initialise()
which checks for opt_watchdog and opt_vpmu_enabled and bail.

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.