Re: [PATCH 2/3] perf: require exclude_guest to use PEBS - kernelside enforcement

From: David Ahern
Date: Thu Sep 13 2012 - 00:33:35 EST

On 9/12/12 8:38 PM, Namhyung Kim wrote:
Hi David,

On Wed, 12 Sep 2012 09:16:29 -0600, David Ahern wrote:
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

Per Peter:
"Intel PEBS in VT-x context uses the DS address as a guest linear address,
even though its programmed by the host as a host linear address. This
either results in guest memory corruption and or the hardware faulting and
'crashing' the virtual machine. Therefore we have to disable PEBS on VT-x
enter and re-enable on VT-x exit, enforcing a strict exclude_guest.

This patch enforces exclude_guest kernel side.

@@ -380,6 +383,9 @@ int x86_pmu_hw_config(struct perf_event *event)
if (event->attr.precise_ip) {
int precise = 0;

+ if (!event->attr.exclude_guest)
+ return -EOPNOTSUPP;

I see a whitespace problem here. :)

grr.... an extra freaking tab.

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