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powerpc/time: Fix KVM host re-arming a timer beyond decrementer range

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If the next host timer is beyond decrementer range, timer_rearm_host_dec
will leave decrementer not programmed. This will not cause a problem for
the host it will just set the decrementer correctly when the decrementer
interrupt hits, it seems safer not to leave the next host decrementer
interrupt timing able to be influenced by a guest.

This code is only used in the P9 KVM paths so it's unlikely to be hit
practically unless large decrementer is force disabled in the host.

Fixes: 25aa145856 ("powerpc/time: add API for KVM to re-arm the host timer/decrementer")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220124143930.3923442-2-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2022-01-25 00:39:29 +10:00 committed by Michael Ellerman
parent 9d71165d39
commit cf74ff52e3
1 changed files with 3 additions and 2 deletions
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5
arch/powerpc/kernel/time.c
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@ -582,8 +582,9 @@ void timer_rearm_host_dec(u64 now)
local_paca->irq_happened |= PACA_IRQ_DEC;
} else {
now = *next_tb - now;
if (now <= decrementer_max)
set_dec_or_work(now);
if (now > decrementer_max)
now = decrementer_max;
set_dec_or_work(now);
}
}
EXPORT_SYMBOL_GPL(timer_rearm_host_dec);