linux-kernel - Re: [PATCH 2/3] perf: require exclude_guest to use PEBS

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Date:	Wed, 12 Sep 2012 22:33:36 -0600
From:	David Ahern <dsahern@...il.com>
To:	Namhyung Kim <namhyung@...nel.org>
CC:	acme@...stprotocols.net, linux-kernel@...r.kernel.org,
	peterz@...radead.org, Ingo Molnar <mingo@...nel.org>,
	Robert Richter <robert.richter@....com>,
	Gleb Natapov <gleb@...hat.com>, Avi Kivity <avi@...hat.com>
Subject: Re: [PATCH 2/3] perf: require exclude_guest to use PEBS - kernel
 side enforcement

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@...radead.org>
>>
>> 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.
>>
> [snip]
>> @@ -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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