linux

iv/linux

History

Vitaly Kuznetsov 77fcbe823f KVM: x86: Prevent 'hv_clock->system_time' from going negative in kvm_guest_time_update()

When guest time is reset with KVM_SET_CLOCK(0), it is possible for
'hv_clock->system_time' to become a small negative number. This happens
because in KVM_SET_CLOCK handling we set 'kvm->arch.kvmclock_offset' based
on get_kvmclock_ns(kvm) but when KVM_REQ_CLOCK_UPDATE is handled,
kvm_guest_time_update() does (masterclock in use case):

hv_clock.system_time = ka->master_kernel_ns + v->kvm->arch.kvmclock_offset;

And 'master_kernel_ns' represents the last time when masterclock
got updated, it can precede KVM_SET_CLOCK() call. Normally, this is not a
problem, the difference is very small, e.g. I'm observing
hv_clock.system_time = -70 ns. The issue comes from the fact that
'hv_clock.system_time' is stored as unsigned and 'system_time / 100' in
compute_tsc_page_parameters() becomes a very big number.

Use 'master_kernel_ns' instead of get_kvmclock_ns() when masterclock is in
use and get_kvmclock_base_ns() when it's not to prevent 'system_time' from
going negative.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210331124130.337992-2-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2021-04-01 05:14:19 -04:00

alpha

io_uring-worker.v3-2021-02-25

2021-02-27 08:29:02 -08:00

arc

arch: setup PF_IO_WORKER threads like PF_KTHREAD

2021-02-21 17:25:22 -07:00

arm

ARM: SoC fixes for v5.12

2021-03-26 11:19:38 -07:00

arm64

KVM/arm64 fixes for 5.12, take #3