* [PATCH v4.9] KVM: PPC: Book3S HV: Fix trap number return from __kvmppc_vcore_entry
@ 2018-05-11 6:35 Paul Mackerras
2018-05-11 6:57 ` Greg KH
0 siblings, 1 reply; 2+ messages in thread
From: Paul Mackerras @ 2018-05-11 6:35 UTC (permalink / raw)
To: stable
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 point where kvmhv_commence_exit is called 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>
---
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 55fbc0c78721..79a180cf4c94 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -299,7 +299,6 @@ 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
/*
@@ -1023,6 +1022,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
secondary_too_late:
li r12, 0
+ stw r12, STACK_SLOT_TRAP(r1)
cmpdi r4, 0
beq 11f
stw r12, VCPU_TRAP(r4)
@@ -1266,12 +1266,12 @@ mc_cont:
bl kvmhv_accumulate_time
#endif
+ 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
@@ -1549,6 +1549,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
* 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 */
@@ -1599,11 +1600,11 @@ 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
@@ -1678,6 +1679,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
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
--
2.11.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v4.9] KVM: PPC: Book3S HV: Fix trap number return from __kvmppc_vcore_entry
2018-05-11 6:35 [PATCH v4.9] KVM: PPC: Book3S HV: Fix trap number return from __kvmppc_vcore_entry Paul Mackerras
@ 2018-05-11 6:57 ` Greg KH
0 siblings, 0 replies; 2+ messages in thread
From: Greg KH @ 2018-05-11 6:57 UTC (permalink / raw)
To: Paul Mackerras; +Cc: stable
On Fri, May 11, 2018 at 04:35:34PM +1000, Paul Mackerras wrote:
> 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 point where kvmhv_commence_exit is called 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>
> ---
> arch/powerpc/kvm/book3s_hv_rmhandlers.S | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
Now applied, thanks.
greg k-h
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2018-05-11 6:35 [PATCH v4.9] KVM: PPC: Book3S HV: Fix trap number return from __kvmppc_vcore_entry Paul Mackerras
2018-05-11 6:57 ` Greg KH
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