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KVM: PPC: Book3S HV: Fix trap number return from __kvmppc_vcore_entry

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commit a8b48a4dccea77e29462e59f1dbf0d5aa1ff167c upstream.

This fixes a bug where the trap number that is returned by
__kvmppc_vcore_entry gets corrupted.  The effect of the corruption
is that IPIs get ignored on POWER9 systems when the IPI is sent via
a doorbell interrupt to a CPU which is executing in a KVM guest.
The effect of the IPI being ignored is often that another CPU locks
up inside smp_call_function_many() (and if that CPU is holding a
spinlock, other CPUs then lock up inside raw_spin_lock()).

The trap number is currently held in register r12 for most of the
assembly-language part of the guest exit path.  In that path, we
call kvmppc_subcore_exit_guest(), which is a C function, without
restoring r12 afterwards.  Depending on the kernel config and the
compiler, it may modify r12 or it may not, so some config/compiler
combinations see the bug and others don't.

To fix this, we arrange for the trap number to be stored on the
stack from the 'guest_bypass:' label until the end of the function,
then the trap number is loaded and returned in r12 as before.

Cc: stable@vger.kernel.org # v4.8+
Fixes: fd7bacbca47a ("KVM: PPC: Book3S HV: Fix TB corruption in guest exit path on HMI interrupt")
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paul Mackerras 2018-03-07 22:17:20 +11:00 committed by Greg Kroah-Hartman
parent 683b4520d0
commit c51eb7379d
1 changed files with 5 additions and 3 deletions
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8
arch/powerpc/kvm/book3s_hv_rmhandlers.S
View File

@ -308,7 +308,6 @@ kvm_novcpu_exit:
stw r12, STACK_SLOT_TRAP(r1)
bl kvmhv_commence_exit
nop
lwz r12, STACK_SLOT_TRAP(r1)
b kvmhv_switch_to_host
/*
@ -1136,6 +1135,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
secondary_too_late:
li r12, 0
stw r12, STACK_SLOT_TRAP(r1)
cmpdi r4, 0
beq 11f
stw r12, VCPU_TRAP(r4)
@ -1445,12 +1445,12 @@ mc_cont:
1:
#endif /* CONFIG_KVM_XICS */
stw r12, STACK_SLOT_TRAP(r1)
mr r3, r12
/* Increment exit count, poke other threads to exit */
bl kvmhv_commence_exit
nop
ld r9, HSTATE_KVM_VCPU(r13)
lwz r12, VCPU_TRAP(r9)
/* Stop others sending VCPU interrupts to this physical CPU */
li r0, -1
@ -1816,6 +1816,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_POWER9_DD1)
* POWER7/POWER8 guest -> host partition switch code.
* We don't have to lock against tlbies but we do
* have to coordinate the hardware threads.
* Here STACK_SLOT_TRAP(r1) contains the trap number.
*/
kvmhv_switch_to_host:
/* Secondary threads wait for primary to do partition switch */
@ -1868,11 +1869,11 @@ BEGIN_FTR_SECTION
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
/* If HMI, call kvmppc_realmode_hmi_handler() */
lwz r12, STACK_SLOT_TRAP(r1)
cmpwi r12, BOOK3S_INTERRUPT_HMI
bne 27f
bl kvmppc_realmode_hmi_handler
nop
li r12, BOOK3S_INTERRUPT_HMI
/*
* At this point kvmppc_realmode_hmi_handler would have resync-ed
* the TB. Hence it is not required to subtract guest timebase
@ -1950,6 +1951,7 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX)
li r0, KVM_GUEST_MODE_NONE
stb r0, HSTATE_IN_GUEST(r13)
lwz r12, STACK_SLOT_TRAP(r1) /* return trap # in r12 */
ld r0, SFS+PPC_LR_STKOFF(r1)
addi r1, r1, SFS
mtlr r0