https://github.com/torvalds/linux
Revision 77fcbe823f002ad18426545351fa2fb94f8d5e61 authored by Vitaly Kuznetsov on 31 March 2021, 12:41:29 UTC, committed by Paolo Bonzini on 01 April 2021, 09:14:19 UTC
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>
1 parent a83829f
Tip revision: 77fcbe823f002ad18426545351fa2fb94f8d5e61 authored by Vitaly Kuznetsov on 31 March 2021, 12:41:29 UTC
KVM: x86: Prevent 'hv_clock->system_time' from going negative in kvm_guest_time_update()
KVM: x86: Prevent 'hv_clock->system_time' from going negative in kvm_guest_time_update()
Tip revision: 77fcbe8
File | Mode | Size |
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arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
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.cocciconfig | -rw-r--r-- | 59 bytes |
.get_maintainer.ignore | -rw-r--r-- | 71 bytes |
.gitattributes | -rw-r--r-- | 62 bytes |
.gitignore | -rw-r--r-- | 1.9 KB |
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COPYING | -rw-r--r-- | 496 bytes |
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MAINTAINERS | -rw-r--r-- | 577.0 KB |
Makefile | -rw-r--r-- | 64.7 KB |
README | -rw-r--r-- | 727 bytes |
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