The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From a8b48a4dccea77e29462e59f1dbf0d5aa1ff167c Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@xxxxxxxxxx>
Date: Wed, 7 Mar 2018 22:17:20 +1100
Subject: [PATCH] KVM: PPC: Book3S HV: Fix trap number return from
__kvmppc_vcore_entry
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@xxxxxxxxxxxxxxx # v4.8+
Fixes: fd7bacbca47a ("KVM: PPC: Book3S HV: Fix TB corruption in guest exit path on HMI interrupt")
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index f31f357b8c5a..d33264697a31 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -320,7 +320,6 @@ 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
/*
@@ -1220,6 +1219,7 @@ 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)
@@ -1558,12 +1558,12 @@ mc_cont:
3: stw r5,VCPU_SLB_MAX(r9)
guest_bypass:
+ 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
@@ -1898,6 +1898,7 @@ 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 */
@@ -1950,12 +1951,12 @@ 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
cmpdi r3, 0
- li r12, BOOK3S_INTERRUPT_HMI
/*
* At this point kvmppc_realmode_hmi_handler may have resync-ed
* the TB, and if it has, we must not subtract the guest timebase
@@ -2008,10 +2009,8 @@ BEGIN_FTR_SECTION
lwz r8, KVM_SPLIT_DO_RESTORE(r3)
cmpwi r8, 0
beq 47f
- stw r12, STACK_SLOT_TRAP(r1)
bl kvmhv_p9_restore_lpcr
nop
- lwz r12, STACK_SLOT_TRAP(r1)
b 48f
47:
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
@@ -2049,6 +2048,7 @@ 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