[PATCH v2] Bug fix - Integer overflow when cpu frequency > u32 max value.

[Neowutran <xen@xxxxxxxxxxxxx>]

xen/x86: prevent overflow with high frequency TSCs

Promote tsc_khz to a 64-bit type before multiplying by 1000 to avoid a
'overflow before widen' bug.
Otherwise just above 4.294GHz the value will overflow.
Processors with clocks this high are now in production and require this to work
correctly.

Signed-off-by: Neowutran <xen@xxxxxxxxxxxxx>
---
Changed since v1:
 * smaller commit message
 * using uint64_t instead of u64
 * added signed-off-by tag
---
 xen/arch/x86/time.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index b01acd390d..c71e79e019 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -2585,7 +2585,7 @@ int tsc_set_info(struct domain *d,
     case TSC_MODE_ALWAYS_EMULATE:
         d->arch.vtsc_offset = get_s_time() - elapsed_nsec;
         d->arch.tsc_khz = gtsc_khz ?: cpu_khz;
-        set_time_scale(&d->arch.vtsc_to_ns, d->arch.tsc_khz * 1000);
+        set_time_scale(&d->arch.vtsc_to_ns, (uint64_t)d->arch.tsc_khz * 1000);
 
         /*
          * In default mode use native TSC if the host has safe TSC and
-- 
2.38.1