Commit 55626ca9 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Paolo Bonzini
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selftests: kvm: Check that TSC page value is small after KVM_SET_CLOCK(0) 



Add a test for the issue when KVM_SET_CLOCK(0) call could cause
TSC page value to go very big because of a signedness issue around
hv_clock->system_time.

Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210326155551.17446-3-vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 77fcbe82

tools/testing/selftests/kvm/x86_64/hyperv_clock.c

+11 −2
Original line number Diff line number Diff line
@@ -80,19 +80,24 @@ static inline void check_tsc_msr_rdtsc(void) 
	GUEST_ASSERT(delta_ns * 100 < (t2 - t1) * 100);

}



static inline u64 get_tscpage_ts(struct ms_hyperv_tsc_page *tsc_page)

{

	return mul_u64_u64_shr64(rdtsc(), tsc_page->tsc_scale) + tsc_page->tsc_offset;

}



static inline void check_tsc_msr_tsc_page(struct ms_hyperv_tsc_page *tsc_page)

{

	u64 r1, r2, t1, t2;



	/* Compare TSC page clocksource with HV_X64_MSR_TIME_REF_COUNT */

	t1 = mul_u64_u64_shr64(rdtsc(), tsc_page->tsc_scale) + tsc_page->tsc_offset;

	t1 = get_tscpage_ts(tsc_page);

	r1 = rdmsr(HV_X64_MSR_TIME_REF_COUNT);



	/* 10 ms tolerance */

	GUEST_ASSERT(r1 >= t1 && r1 - t1 < 100000);

	nop_loop();



	t2 = mul_u64_u64_shr64(rdtsc(), tsc_page->tsc_scale) + tsc_page->tsc_offset;

	t2 = get_tscpage_ts(tsc_page);

	r2 = rdmsr(HV_X64_MSR_TIME_REF_COUNT);

	GUEST_ASSERT(r2 >= t1 && r2 - t2 < 100000);

}
@@ -130,7 +135,11 @@ static void guest_main(struct ms_hyperv_tsc_page *tsc_page, vm_paddr_t tsc_page_ 


	tsc_offset = tsc_page->tsc_offset;

	/* Call KVM_SET_CLOCK from userspace, check that TSC page was updated */



	GUEST_SYNC(7);

	/* Sanity check TSC page timestamp, it should be close to 0 */

	GUEST_ASSERT(get_tscpage_ts(tsc_page) < 100000);



	GUEST_ASSERT(tsc_page->tsc_offset != tsc_offset);



	nop_loop();