linux-kernel - Re: [kvm-unit-tests PATCH] x86: pmu: Test full-width counter writes support

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Date:   Tue, 16 Jun 2020 14:28:51 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Thomas Huth <thuth@...hat.com>, Like Xu <like.xu@...ux.intel.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [kvm-unit-tests PATCH] x86: pmu: Test full-width counter writes
 support

On 16/06/20 12:49, Thomas Huth wrote:
> On 29/05/2020 09.43, Like Xu wrote:
>> When the full-width writes capability is set, use the alternative MSR
>> range to write larger sign counter values (up to GP counter width).
>>
>> Signed-off-by: Like Xu <like.xu@...ux.intel.com>
>> ---
>>  lib/x86/msr.h |   1 +
>>  x86/pmu.c     | 125 ++++++++++++++++++++++++++++++++++++++++----------
>>  2 files changed, 102 insertions(+), 24 deletions(-)
> [...]
>> @@ -452,6 +468,66 @@ static void check_running_counter_wrmsr(void)
>>  	report_prefix_pop();
>>  }
>>  
>> +static void check_counters(void)
>> +{
>> +	check_gp_counters();
>> +	check_fixed_counters();
>> +	check_rdpmc();
>> +	check_counters_many();
>> +	check_counter_overflow();
>> +	check_gp_counter_cmask();
>> +	check_running_counter_wrmsr();
>> +}
>> +
>> +static void do_unsupported_width_counter_write(void *index)
>> +{
>> +	wrmsr(MSR_IA32_PMC0 + *((int *) index), 0xffffff0123456789ull);
>> +}
>> +
>> +static void  check_gp_counters_write_width(void)
>> +{
>> +	u64 val_64 = 0xffffff0123456789ull;
>> +	u64 val_32 = val_64 & ((1ul << 32) - 1);
>  Hi,
> 
> this broke compilation on 32-bit hosts:
> 
>  https://travis-ci.com/github/huth/kvm-unit-tests/jobs/349654654#L710
> 
> Fix should be easy, I guess - either use 1ull or specify the mask
> 0xffffffff directly.

Or

u64 val_32 = (u64)(u32) val_64;

I'll send a patch.

Paolo