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author | Keir Fraser <keir.fraser@citrix.com> | 2008-10-20 15:11:19 +0100 |
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committer | Keir Fraser <keir.fraser@citrix.com> | 2008-10-20 15:11:19 +0100 |
commit | 4fe64c10cb285a270ba9a7b630ed33b009f0c633 (patch) | |
tree | a6fb5de4a07bf28dd3fadcac7d72b5ab1375a854 /xen/arch/x86/nmi.c | |
parent | 942da08c6c66aa8ebd0db4d7cbe0b06426bc6c53 (diff) | |
download | xen-4fe64c10cb285a270ba9a7b630ed33b009f0c633.tar.gz xen-4fe64c10cb285a270ba9a7b630ed33b009f0c633.tar.bz2 xen-4fe64c10cb285a270ba9a7b630ed33b009f0c633.zip |
NMI watchdog: don't try to run too slow.
The way MSR writes of performance counters works means that Intel
CPUs running faster than about 2.1GHz can't set the NMI timer to 1Hz.
Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
Diffstat (limited to 'xen/arch/x86/nmi.c')
-rw-r--r-- | xen/arch/x86/nmi.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/xen/arch/x86/nmi.c b/xen/arch/x86/nmi.c index 47e53b2a2a..edc323cd38 100644 --- a/xen/arch/x86/nmi.c +++ b/xen/arch/x86/nmi.c @@ -122,10 +122,17 @@ int __init check_nmi_watchdog (void) printk("\n"); - /* now that we know it works we can reduce NMI frequency to - something more reasonable; makes a difference in some configs */ + /* + * Now that we know it works we can reduce NMI frequency to + * something more reasonable; makes a difference in some configs. + * There's a limit to how slow we can go because writing the perfctr + * MSRs only sets the low 32 bits, with the top 8 bits sign-extended + * from those, so it's not possible to set up a delay larger than + * 2^31 cycles and smaller than (2^40 - 2^31) cycles. + * (Intel SDM, section 18.22.2) + */ if ( nmi_watchdog == NMI_LOCAL_APIC ) - nmi_hz = 1; + nmi_hz = max(1ul, cpu_khz >> 20); return 0; } |