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KVM: PPC: Book3S HV: Fix case where HDEC is treated as 32-bit on POWER9

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Commit 2f2724630f ("KVM: PPC: Book3S HV: Cope with host using large
decrementer mode", 2017-05-22) added code to treat the hypervisor
decrementer (HDEC) as a 64-bit value on POWER9 rather than 32-bit.
Unfortunately, that commit missed one place where HDEC is treated
as a 32-bit value.  This fixes it.

This bug should not have any user-visible consequences that I can
think of, beyond an occasional unnecessary exit to the host kernel.
If the hypervisor decrementer has gone negative, then the bottom
32 bits will be negative for about 4 seconds after that, so as
long as we get out of the guest within those 4 seconds we won't
conclude that the HDEC interrupt is spurious.

Reported-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Fixes: 2f2724630f ("KVM: PPC: Book3S HV: Cope with host using large decrementer mode")
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Paul Mackerras 2017-08-25 19:52:12 +10:00
parent 0bfa33c7f7
commit a4faf2e77a
1 changed files with 2 additions and 1 deletions
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3
arch/powerpc/kvm/book3s_hv_rmhandlers.S
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@ -1280,7 +1280,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
cmpwi r12,BOOK3S_INTERRUPT_HV_DECREMENTER
bne 2f
mfspr r3,SPRN_HDEC
cmpwi r3,0
EXTEND_HDEC(r3)
cmpdi r3,0
mr r4,r9
bge fast_guest_return
2: