Re: [PATCH RFC 3/3] xtf: add minimal HPET functionality test

[Wei Liu <wei.liu2@citrix.com>]

On Fri, Feb 23, 2018 at 01:27:43PM +0000, Roger Pau Monne wrote:
> Add a basic HPET functionality test, note that this test requires the
> HPET to support level triggered interrupts.
> 
> Further improvements should add support for interrupt delivery, and
> testing all the available timers.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> ---
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
>  arch/x86/include/arch/lib.h |  14 ++++
>  docs/all-tests.dox          |   2 +
>  tests/hpet/Makefile         |   9 +++
>  tests/hpet/main.c           | 187 ++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 212 insertions(+)
>  create mode 100644 tests/hpet/Makefile
>  create mode 100644 tests/hpet/main.c
> 
> diff --git a/arch/x86/include/arch/lib.h b/arch/x86/include/arch/lib.h
> index 6714bdc..3400890 100644
> --- a/arch/x86/include/arch/lib.h
> +++ b/arch/x86/include/arch/lib.h
> @@ -392,6 +392,20 @@ static inline void write_xcr0(uint64_t xcr0)
>      xsetbv(0, xcr0);
>  }
>  
> +static inline uint64_t rdtsc(void)
> +{
> +    uint32_t low, high;
> +
> +    asm volatile ("rdtsc" : "=a" (low), "=d" (high));
> +

You probably need to add lfence or mfence. See rdtsc_ordered in Xen.

> +    return ((uint64_t)high << 32) | low;
> +}
> +
[...]
> +static void set_freq(void)
> +{
> +    uint32_t eax, ebx, ecx, edx, base;
> +    bool found = false;
> +
> +    /* Get tsc frequency from cpuid. */
> +    for ( base = XEN_CPUID_FIRST_LEAF;
> +          base < XEN_CPUID_FIRST_LEAF + 0x10000; base += 0x100 )
> +    {
> +        cpuid(base, &eax, &ebx, &ecx, &edx);
> +
> +        if ( (ebx == XEN_CPUID_SIGNATURE_EBX) &&
> +             (ecx == XEN_CPUID_SIGNATURE_ECX) &&
> +             (edx == XEN_CPUID_SIGNATURE_EDX) &&
> +             ((eax - base) >= 2) )
> +        {
> +            found = true;
> +            break;
> +        }
> +    }
> +
> +    if ( !found )
> +        panic("Unable to locate Xen CPUID leaves\n");
> +

Finding Xen leaves should live in its own function and move to common
code if possible.

> +    cpuid_count(base + 3, 0, &eax, &ebx, &freq, &edx);
> +    printk("TSC frequency %ukHz\n", freq);
> +}
> +
> +/* Busy-wait implementation based on tsc value. */
> +static void wait(unsigned int ms)
> +{
> +    uint64_t end = rdtsc() + (uint64_t)ms * (uint64_t)freq;
> +
> +    while ( rdtsc() < end )
> +        pause();
> +}

Rename to mdelay and move to a helper file?

> +
> +void test_main(void)
> +{
[...]
> +    HPET_REG(HPET_Tn_CFG(nr)) &= ~HPET_TN_LEVEL;
> +    HPET_REG(HPET_STATUS) = 1 << nr;
> +    wait(200);
> +    if ( ((HPET_REG(HPET_STATUS) >> nr) & 1) )
> +        return xtf_failure("Fail: Status bit set for edge interrupt in periodic mode\n");
> +

Is it possible to use shorter time in the test? This test as-is will run
for 1 or 2 seconds which is a bit long as micro-kernel testing.

Wei.

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