| Message ID | 20160617154914.660326-1-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 17/06/2016 17:48, Arnd Bergmann wrote: > 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> > --- > arch/x86/kvm/x86.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 53241618e3c9..f79c86510408 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1163,7 +1163,7 @@ 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; > @@ -1186,13 +1186,13 @@ 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; > > Queued, thanks. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 53241618e3c9..f79c86510408 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1163,7 +1163,7 @@ 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; @@ -1186,13 +1186,13 @@ 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;
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> --- arch/x86/kvm/x86.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)