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Date: Fri, 12 Apr 2024 01:19:13 -0700
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Subject: Re: [PATCH v2 2/2] KVM: selftests: Add KVM/PV clock selftest to prove
 timer correction
To: Jack Allister <jalliste@amazon.com>
Cc: bp@alien8.de, corbet@lwn.net, dave.hansen@linux.intel.com,
        dwmw2@infradead.org, hpa@zytor.com, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        mingo@redhat.com, paul@xen.org, pbonzini@redhat.com, seanjc@google.com,
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References: <20240408220705.7637-1-jalliste@amazon.com>
 <20240410095244.77109-1-jalliste@amazon.com>
 <20240410095244.77109-3-jalliste@amazon.com>
Content-Language: en-US
From: Dongli Zhang <dongli.zhang@oracle.com>
In-Reply-To: <20240410095244.77109-3-jalliste@amazon.com>
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On 4/10/24 02:52, Jack Allister wrote:
> A VM's KVM/PV clock has an inherent relationship to it's TSC (guest). When
> either the host system live-updates or the VM is live-migrated this pairing
> of the two clock sources should stay the same.
> 

[snip]

> +
> +int main(int argc, char *argv[])
> +{
> +	struct kvm_vcpu *vcpu;
> +	struct kvm_vm *vm;
> +	bool scale_tsc;
> +
> +	scale_tsc = argc > 1 && (!strncmp(argv[1], "-s", 3) ||
> +				 !strncmp(argv[1], "--scale-tsc", 10));
> +
> +	TEST_REQUIRE(sys_clocksource_is_based_on_tsc());
> +
> +	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
> +
> +	configure_pvclock(vm, vcpu);
> +
> +	if (scale_tsc)
> +		configure_scaled_tsc(vcpu);
> +
> +	run_test(vm, vcpu);
> +
> +	return 0;
> +}

David suggested make the scale_tsc automatically based on the availability of
the feature.

Therefore, if there is going to be v3, I suggest add kvm_vm_free() explicitly
(similar to close(fd)).

Thank you very much!

Dongli Zhang