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Re: [Qemu-devel] arm64 qemu tests failing in linux-next since 'arm64: ke
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From: |
Peter Maydell |
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Subject: |
Re: [Qemu-devel] arm64 qemu tests failing in linux-next since 'arm64: kernel: enforce pmuserenr_el0 initialization and restore' |
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Date: |
Thu, 7 Jan 2016 15:58:15 +0000 |
On 7 January 2016 at 15:53, Lorenzo Pieralisi <address@hidden> wrote:
> On Thu, Jan 07, 2016 at 01:25:35PM +0000, Peter Maydell wrote:
>> We had previously been relying on the kernel not attempting to
>> touch the PMU if the ID_AA64DFR0_EL1 PMUVer bits read 0000
>> ("Performance Monitors extension System registers not implemented").
>
> Ok, thanks for looking into this. I wonder why reading pmcr_el0 does
> not suffer from the same problem though.
Just a pragmatic thing on QEMU's end, I expect -- the kernel already
touched PMCR_EL0 and we wanted to be able to boot it, so we have an
implementation of it.
thanks
-- PMM