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Message-ID: <bc650fac-702c-e554-43ca-9cd3cfed9696@codeaurora.org> Date: Wed, 6 Dec 2017 16:19:24 -0500 From: "Leeder, Neil" <nleeder@...eaurora.org> To: Mark Rutland <mark.rutland@....com> Cc: nleeder@...eaurora.org, Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, Mark Langsdorf <mlangsdo@...hat.com>, Mark Salter <msalter@...hat.com>, Jon Masters <jcm@...hat.com>, Timur Tabi <timur@...eaurora.org>, Mark Brown <broonie@...nel.org> Subject: Re: [PATCH] perf: qcom_l2_pmu: don't allow guest access On 12/6/2017 11:11 AM, Mark Rutland wrote: > On Wed, Dec 06, 2017 at 10:55:33AM -0500, Neil Leeder wrote: >> Guests cannot access IMPDEF system registers, which are used >> by this driver. Disable the driver if it's running in a guest VM. >> >> Signed-off-by: Neil Leeder <nleeder@...eaurora.org> >> --- >> drivers/perf/qcom_l2_pmu.c | 4 ++++ >> 1 file changed, 4 insertions(+) > > Hi Neil, > > I'm a little confused by this. Why is this hypervisor providing a > QCOM8130 device to the guest that it cannot use? > > Could you elaborate on what's going on? > Hi Mark, While there's an argument that the guest shouldn't be loading the driver in the first place, we can't control everyone's guest configuration or what their hypervisor does. >> >> diff --git a/drivers/perf/qcom_l2_pmu.c b/drivers/perf/qcom_l2_pmu.c >> index 4fdc848..49dc954 100644 >> --- a/drivers/perf/qcom_l2_pmu.c >> +++ b/drivers/perf/qcom_l2_pmu.c >> @@ -1057,6 +1057,10 @@ static int __init register_l2_cache_pmu_driver(void) >> { >> int err; >> >> + /* Don't enable driver if running as guest */ >> + if (!is_hyp_mode_available()) >> + return 0; >> + >> err = cpuhp_setup_state_multi(CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE, >> "AP_PERF_ARM_QCOM_L2_ONLINE", >> l2cache_pmu_online_cpu, >> -- >> Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies Inc. >> Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, >> a Linux Foundation Collaborative Project. >> Neil -- Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
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