mftb is serialising (dispatch next-to-complete) so it is heavy weight
for a mfspr. Avoid reading it multiple times in the entry or exit paths.
A small number of cycles delay to timers is tolerable.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-7-npiggin@gmail.com
*
* XXX: Another day's problem.
*/
- mtspr(SPRN_DEC, vcpu->arch.dec_expires - mftb());
+ mtspr(SPRN_DEC, vcpu->arch.dec_expires - tb);
if (kvmhv_on_pseries()) {
/*
vc->in_guest = 0;
next_timer = timer_get_next_tb();
- set_dec(next_timer - mftb());
+ set_dec(next_timer - tb);
/* We may have raced with new irq work */
if (test_irq_work_pending())
set_dec(1);
unsigned long host_dawr1;
unsigned long host_dawrx1;
- hdec = time_limit - mftb();
+ tb = mftb();
+ hdec = time_limit - tb;
if (hdec < 0)
return BOOK3S_INTERRUPT_HV_DECREMENTER;
vcpu->arch.ceded = 0;
if (vc->tb_offset) {
- u64 new_tb = mftb() + vc->tb_offset;
+ u64 new_tb = tb + vc->tb_offset;
mtspr(SPRN_TBU40, new_tb);
tb = mftb();
if ((tb & 0xffffff) < (new_tb & 0xffffff))