| Message ID | 20201230160208.18877-1-andrew.cooper3@citrix.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | x86/hpet: Fix return value of hpet_setup() | expand |
On Wed, Dec 30, 2020 at 04:02:08PM +0000, Andrew Cooper wrote: > hpet_setup() is idempotent if the rate has already been calculated, and > returns the cached value. However, this only works correctly when the return > statements are identical. > > Use a sensibly named local variable, rather than a dead one with a bad name. > > Fixes: a60bb68219 ("x86/time: reduce rounding errors in calculations") > Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com> Thanks, Roger.
diff --git a/xen/arch/x86/hpet.c b/xen/arch/x86/hpet.c index a55e68e6f7..e6fab8acd8 100644 --- a/xen/arch/x86/hpet.c +++ b/xen/arch/x86/hpet.c @@ -759,7 +759,7 @@ u64 __init hpet_setup(void) { static u64 __initdata hpet_rate; u32 hpet_id, hpet_period; - unsigned int last; + unsigned int last, rem; if ( hpet_rate ) return hpet_rate; @@ -789,9 +789,11 @@ u64 __init hpet_setup(void) hpet_resume(hpet_boot_cfg); hpet_rate = 1000000000000000ULL; /* 10^15 */ - last = do_div(hpet_rate, hpet_period); + rem = do_div(hpet_rate, hpet_period); + if ( (rem * 2) > hpet_period ) + hpet_rate++; - return hpet_rate + (last * 2 > hpet_period); + return hpet_rate; } void hpet_resume(u32 *boot_cfg)
hpet_setup() is idempotent if the rate has already been calculated, and returns the cached value. However, this only works correctly when the return statements are identical. Use a sensibly named local variable, rather than a dead one with a bad name. Fixes: a60bb68219 ("x86/time: reduce rounding errors in calculations") Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> --- CC: Jan Beulich <JBeulich@suse.com> CC: Roger Pau Monné <roger.pau@citrix.com> CC: Wei Liu <wl@xen.org> --- xen/arch/x86/hpet.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)