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kvm: x86: use getboottime64

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KVM reads the current boottime value as a struct timespec in order to
calculate the guest wallclock time, resulting in an overflow in 2038
on 32-bit systems.

The data then gets passed as an unsigned 32-bit number to the guest,
and that in turn overflows in 2106.

We cannot do much about the second overflow, which affects both 32-bit
and 64-bit hosts, but we can ensure that they both behave the same
way and don't overflow until 2106, by using getboottime64() to read
a timespec64 value.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Arnd Bergmann 2016-06-17 17:48:56 +02:00 committed by Paolo Bonzini
parent c45dcc71b7
commit 87aeb54f1b
1 changed files with 5 additions and 5 deletions
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10
arch/x86/kvm/x86.c
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@ -1165,7 +1165,7 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
int version;
int r;
struct pvclock_wall_clock wc;
struct timespec boot;
struct timespec64 boot;
if (!wall_clock)
return;
@ -1188,13 +1188,13 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
* wall clock specified here. guest system time equals host
* system time for us, thus we must fill in host boot time here.
*/
getboottime(&boot);
getboottime64(&boot);
if (kvm->arch.kvmclock_offset) {
struct timespec ts = ns_to_timespec(kvm->arch.kvmclock_offset);
boot = timespec_sub(boot, ts);
struct timespec64 ts = ns_to_timespec64(kvm->arch.kvmclock_offset);
boot = timespec64_sub(boot, ts);
}
wc.sec = boot.tv_sec;
wc.sec = (u32)boot.tv_sec; /* overflow in 2106 guest time */
wc.nsec = boot.tv_nsec;
wc.version = version;