From: Anton Romanov romanton@google.com
[ Upstream commit 3a55f729240a686aa8af00af436306c0cd532522 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kvm/x86.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c6eb3e45e3d8..e8f495b9ae10 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8770,6 +8770,13 @@ 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;