From: Bijan Mottahedeh <bijan.mottahedeh@oracle.com>
To: Richard Henderson <richard.henderson@linaro.org>, qemu-devel@nongnu.org
Cc: kvmarm@lists.cs.columbia.edu, Karl Heubaum <karl.heubaum@oracle.com>
Subject: Re: [Qemu-devel] [RFC QEMU 1/2] arm/virt: Initialize generic timer scale factor dynamically
Date: Fri, 9 Nov 2018 19:12:08 -0800 [thread overview]
Message-ID: <7cfea6b6-b0eb-f276-edc7-da2e7f77ded0@oracle.com> (raw)
In-Reply-To: <47f78310-56e7-ba5e-0fb1-99830750e49b@linaro.org>
On 11/8/2018 6:21 AM, Richard Henderson wrote:
> On 11/7/18 7:48 PM, Bijan Mottahedeh wrote:
>>
>> +static void set_system_clock_scale(void)
>> +{
>> + unsigned long cntfrq_el0;
>> +
>> + asm volatile("mrs %0, cntfrq_el0" : "=r"(cntfrq_el0));
>> +
>> + if (cntfrq_el0 == 0) {
>> + cntfrq_el0 = GTIMER_SCALE_DEF;
>> + }
>> +
>> + system_clock_scale = NANOSECONDS_PER_SECOND / (int)cntfrq_el0;
>> +}
> This only works for kvm.
>
> For TCG you need to use the default always. In particular, it won't even
> compile for an x86 host.
>
>
> r~
Is it ok to ifdef the asm statement with CONFIG_KVM, or what would be
the correct way to account for TCG vs. KVM?
Thanks.
--bijan
next prev parent reply other threads:[~2018-11-10 3:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-07 18:48 [Qemu-devel] [RFC QEMU 0/2] arm/virt: Account for guest pause time Bijan Mottahedeh
2018-11-07 18:48 ` [Qemu-devel] [RFC QEMU 1/2] arm/virt: Initialize generic timer scale factor dynamically Bijan Mottahedeh
2018-11-08 14:21 ` Richard Henderson
2018-11-10 3:12 ` Bijan Mottahedeh [this message]
2018-11-07 18:48 ` [Qemu-devel] [RFC QEMU 2/2] arm/virt: Account for guest pause time Bijan Mottahedeh
2018-11-08 14:32 ` [Qemu-devel] [RFC QEMU 0/2] " no-reply
2018-11-08 14:34 ` no-reply
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