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kvm: kvmclock: let KVM_GET_CLOCK return whether the master clock is in use

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Userspace can read the exact value of kvmclock by reading the TSC
and fetching the timekeeping parameters out of guest memory.  This
however is brittle and not necessary anymore with KVM 4.11.  Provide
a mechanism that lets userspace know if the new KVM_GET_CLOCK
semantics are in effect, and---since we are at it---if the clock
is stable across all VCPUs.

Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Paolo Bonzini
2016-11-09 17:48:15 +01:00
committed by Radim Krčmář
parent 1650b4ebc9
commit e3fd9a93a1
3 changed files with 25 additions and 3 deletions
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7
include/uapi/linux/kvm.h
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@@ -972,12 +972,19 @@ struct kvm_irqfd {
__u8 pad[16];
};
/* For KVM_CAP_ADJUST_CLOCK */
/* Do not use 1, KVM_CHECK_EXTENSION returned it before we had flags. */
#define KVM_CLOCK_TSC_STABLE 2
struct kvm_clock_data {
__u64 clock;
__u32 flags;
__u32 pad[9];
};
/* For KVM_CAP_SW_TLB */
#define KVM_MMU_FSL_BOOKE_NOHV 0
#define KVM_MMU_FSL_BOOKE_HV 1