| Message ID | d018f50f439c4d8dff8add022d28698a2af3c320.1671365645.git.xen@neowutran.ovh (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] Bug fix - Integer overflow when cpu frequency > u32 max value. | expand |
On Sun, Dec 18, 2022 at 01:14:07PM +0100, Neowutran wrote: > 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@neowutran.ovh> Needing a bit of word-wrapping, but that can be adjusted during commit to the Xen tree. This strikes me as urgent for an updated Xen release. In the past 3 months, both large manufacturers of desktop processors have released processors with sufficient clock speed to require this patch. This WILL trigger *massive* numbers of bug reports very soon. Similarly I suggest all Linux distributions which distribute Xen will want to issue updates urgently.
On 18.12.2022 22:47, Elliott Mitchell wrote: > On Sun, Dec 18, 2022 at 01:14:07PM +0100, Neowutran wrote: >> 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@neowutran.ovh> > > Needing a bit of word-wrapping, but that can be adjusted during commit to > the Xen tree. Right - also the first line of the body really wants to be the title. I'd be happy to make edits while committing, but as said in reply to v1 I also would prefer to suffix the literal "1000" instead of adding a cast. I'd also be happy to make that adjustment (including to the description), but I'd prefer to do so with your agreement. Jan
On 2022-12-19 09:12, Jan Beulich wrote: > On 18.12.2022 22:47, Elliott Mitchell wrote: > > On Sun, Dec 18, 2022 at 01:14:07PM +0100, Neowutran wrote: > >> xen/x86: prevent overflow with high frequency TSCs > >> > >> Pr
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
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@neowutran.ovh> --- 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(-)