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Re: [Minios-devel] [UNIKRAFT PATCHv4 23/43] plat/kvm: Add Arm64 virtual timer library to provide ticks





On 10/07/18 09:23, Wei Chen wrote:
Hi Julien,

Hi Wei,

diff --git a/plat/kvm/arm/time.c b/plat/kvm/arm/time.c
new file mode 100644
index 0000000..ab4968f
--- /dev/null
+++ b/plat/kvm/arm/time.c

The timer is generic on Arm. How about moving that to common arm64 code?


I am re-implementing a timer library for Arm64 to support scheduler.
Current timer library just to provide ukplat_monotonic_clock to
make uk_printd can print timestamp.

I will place the new library to common code.

You can probably place it in common Arm (32-bit and 64-bit) code.


@@ -0,0 +1,127 @@
+/* SPDX-License-Identifier: BSD-3-Clause */

Same remark as before for SPDX.

+/*
+ * Authors: Wei Chen <Wei.Chen@xxxxxxx>
+ *
+ * Copyright (c) 2018, Arm Ltd. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS
BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THIS HEADER MAY NOT BE EXTRACTED OR MODIFIED IN ANY WAY.
+ */
+#include <stdlib.h>
+#include <uk/assert.h>
+#include <uk/plat/time.h>
+
+static uint64_t cntvct_at_init;

How about boot_ticks here?

Not a big problem, OK.


+static uint32_t counter_freq;
+/*
+ * Shift factor for TSC scaling multiplier; referred to as S in the
following

TSC has no meaning on Arm.

Time Stamp Counter is a neutral word, I don't think it has obvious
architecture characteristic. But if you think the abbreviation TSC
is conflict/confused with x86's RDTSC, I would not use the abbreviation.

To be honest I never heard that word outside of x86 until your e-mail :). And wikipedia seems to disagree with you:

https://en.wikipedia.org/wiki/Time_Stamp_Counter

[...]


I don't understand it either ; ) This comment existed in mini-os arm32
timer originally. And have been copied to lots of projects, I just copied
it from one of these projects.

My advice about Mini-OS arm32: Don't trust it! :)

Cheers,

--
Julien Grall

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