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Re: [Qemu-devel] [PATCH] timer.h: Provide monotonic time for ARM guests

From: Pranith Kumar
Subject: Re: [Qemu-devel] [PATCH] timer.h: Provide monotonic time for ARM guests
Date: Tue, 18 Apr 2017 15:19:16 -0400

On Tue, Apr 18, 2017 at 5:56 AM, Paolo Bonzini <address@hidden> wrote:
> On 17/04/2017 20:55, Pranith Kumar wrote:
>>>> +/* ARM does not have a user-space readble cycle counter available.
>>>> + * This is a compromise to get monotonically increasing time.
>>>> + */
>>>> +static inline int64_t cpu_get_host_ticks(void)
>>>> +{
>>>> +    return get_clock();
>>>> +}
>>> This doesn't look like it should be ARM-specific. Is it
>>> better than the current default implementation? If so,
>>> why not make this the default implementation?
>> I think we can do that...
> Yes, it is always better for emulation accuracy.  It may be much slower,
> depending on your OS (especially if get_clock requires a
> user->kernel->user transition), but the current code is quite broken.

OK, I sent an updated patch using get_clock() for all other cases.


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