When I was doing PTP_SYS_OFFSET_PRECISE ioctl in VM which has 128 vCPUs, I got error returned occasionally. Then I checked the routine of "getcrosststamp". I found in kvm_arch_ptp_get_crosststamp() of x86, pvclock vcpu time info was got from hv_clock arrary which has only 64 elements. Hence this ioctl is executed on vCPU > 64, a wild/dangling pointer will be got, which had casued the error. To confirm this finding, I wrote a simple PTP_SYS_OFFSET_PRECISE ioctl test and used "taskset -c n" to run the test, when it was executed on vCPUs >= 64 it returned error. This patchset exposes this_cpu_pvti() to get per cpu pvclock vcpu time info of vCPUs >= 64 insdead of getting them from hv_clock arrary.
Zelin Deng (2): x86/kvmclock: Move this_cpu_pvti into kvmclock.h ptp: Fix ptp_kvm_getcrosststamp issue for x86 ptp_kvm
arch/x86/include/asm/kvmclock.h | 14 ++++++++++++++ arch/x86/kernel/kvmclock.c | 13 ++----------- drivers/ptp/ptp_kvm_x86.c | 9 ++------- 3 files changed, 18 insertions(+), 18 deletions(-)