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kvm: x86: Disable KVM_HC_CLOCK_PAIRING if tsc is in always catchup mode 

If vcpu has tsc_always_catchup set each request updates pvclock data.
KVM_HC_CLOCK_PAIRING consumers such as ptp_kvm_x86 rely on tsc read on
host's side and do hypercall inside pvclock_read_retry loop leading to
infinite loop in such situation.

v3:
    Removed warn
    Changed return code to KVM_EFAULT
v2:
    Added warn

Signed-off-by: Anton Romanov <romanton@google.com>
Message-Id: <20220216182653.506850-1-romanton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Anton Romanov 2022-02-16 18:26:54 +00:00 committed by Paolo Bonzini
parent 4cb9a998b1
commit 3a55f72924
1 changed files with 7 additions and 0 deletions
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7
arch/x86/kvm/x86.c
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@ -8943,6 +8943,13 @@ static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
return -KVM_EOPNOTSUPP;
/*
* When tsc is in permanent catchup mode guests won't be able to use
* pvclock_read_retry loop to get consistent view of pvclock
*/
if (vcpu->arch.tsc_always_catchup)
return -KVM_EOPNOTSUPP;
if (!kvm_get_walltime_and_clockread(&ts, &cycle))
return -KVM_EOPNOTSUPP;