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@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From a8b48a4dccea77e29462e59f1dbf0d5aa1ff167c Mon Sep 17 00:00:00 2001
From: Paul Mackerras paulus@ozlabs.org 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@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
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