64-bit Book3S exception handlers must find the dynamic kernel base
to add to the target address when branching beyond __end_interrupts,
in order to support kernel running at non-0 physical address.
Support this in KVM by branching with CTR, similarly to regular
interrupt handlers. The guest CTR saved in HSTATE_SCRATCH2 and
restored after the branch.
Without this, the host kernel hangs and crashes randomly when it is
running at a non-0 address and a KVM guest is started.
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
arch/powerpc/include/asm/exception-64s.h | 39 ++++++++++++++++++++++++++++++--
arch/powerpc/include/asm/head-64.h | 2 +-
arch/powerpc/kernel/exceptions-64s.S | 4 ++--
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 6 +++++
arch/powerpc/kvm/book3s_segment.S | 5 ++++
5 files changed, 51 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/include/asm/exception-64s.h
b/arch/powerpc/include/asm/exception-64s.h
index bc8fc45..000b317 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -97,6 +97,11 @@
ld reg,PACAKBASE(r13); \
ori reg,reg,(ABS_ADDR(label))@l;
+#define __LOAD_FAR_HANDLER(reg, label) \
+ ld reg,PACAKBASE(r13); \
+ ori reg,reg,(ABS_ADDR(label))@l; \
+ addis reg,reg,(ABS_ADDR(label))@h;
+
/* Exception register prefixes */
#define EXC_HV H
#define EXC_STD
@@ -227,12 +232,42 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
mtctr reg; \
bctr
+/*
+ * KVM requires >64K branches when branching from unrelocated code.
+ */
+#define BRANCH_TO_KVM_EXIT(reg, label) \
+ mfctr reg; \
+ std reg,HSTATE_SCRATCH2(r13); \
+ __LOAD_FAR_HANDLER(reg, label); \
+ mtctr reg; \
+ bctr
+
+#define BRANCH_TO_KVM(reg, label) \
+ __LOAD_FAR_HANDLER(reg, label); \
+ mtctr reg; \
+ bctr
+
+#define BRANCH_LINK_TO_KVM(reg, label) \
+ __LOAD_FAR_HANDLER(reg, label); \
+ mtctr reg; \
+ bctrl
+
#else
#define BRANCH_TO_COMMON(reg, label) \
b label
+#define BRANCH_TO_KVM(reg, label) \
+ b label
+
+#define BRANCH_TO_KVM_EXIT(reg, label) \
+ b label
+
+#define BRANCH_LINK_TO_KVM(reg, label) \
+ bl label
+
#endif
+
#define __KVM_HANDLER(area, h, n) \
BEGIN_FTR_SECTION_NESTED(947) \
ld r10,area+EX_CFAR(r13); \
@@ -249,7 +284,7 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
or r12,r12,r9; \
ld r9,area+EX_R9(r13); \
std r9,HSTATE_SCRATCH1(r13); \
- b kvmppc_interrupt
+ BRANCH_TO_KVM_EXIT(r9, kvmppc_interrupt)
#define __KVM_HANDLER_SKIP(area, h, n) \
cmpwi r10,KVM_GUEST_MODE_SKIP; \
@@ -265,7 +300,7 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
or r12,r12,r9; \
ld r9,area+EX_R9(r13); \
std r9,HSTATE_SCRATCH1(r13); \
- b kvmppc_interrupt; \
+ BRANCH_TO_KVM_EXIT(r9, kvmppc_interrupt); \
89: mtocrf 0x80,r9; \
ld r9,area+EX_R9(r13); \
ld r10,area+EX_R10(r13); \
diff --git a/arch/powerpc/include/asm/head-64.h
b/arch/powerpc/include/asm/head-64.h
index f7131cf..a5cbc1c 100644
--- a/arch/powerpc/include/asm/head-64.h
+++ b/arch/powerpc/include/asm/head-64.h
@@ -228,7 +228,7 @@ end_##sname:
#ifdef CONFIG_KVM_BOOK3S_64_HANDLER
#define TRAMP_KVM_BEGIN(name) \
- TRAMP_REAL_BEGIN(name)
+ TRAMP_VIRT_BEGIN(name)
#else
#define TRAMP_KVM_BEGIN(name)
#endif
diff --git a/arch/powerpc/kernel/exceptions-64s.S
b/arch/powerpc/kernel/exceptions-64s.S
index 5faff1c..955fc76 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -142,7 +142,7 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
lbz r0,HSTATE_HWTHREAD_REQ(r13)
cmpwi r0,0
beq 1f
- b kvm_start_guest
+ BRANCH_TO_KVM(r10, kvm_start_guest)
1:
#endif
@@ -977,7 +977,7 @@ TRAMP_REAL_BEGIN(hmi_exception_early)
EXCEPTION_PROLOG_COMMON_2(PACA_EXGEN)
EXCEPTION_PROLOG_COMMON_3(0xe60)
addi r3,r1,STACK_FRAME_OVERHEAD
- bl hmi_exception_realmode
+ BRANCH_LINK_TO_KVM(r4, hmi_exception_realmode)
/* Windup the stack. */
/* Move original HSRR0 and HSRR1 into the respective regs */
ld r9,_MSR(r1)
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 0536c73..1d07cea 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1047,8 +1047,14 @@ kvmppc_interrupt_hv:
* R13 = PACA
* R9 = unused
* guest R12, R9 saved in shadow VCPU SCRATCH0/1 respectively
+ * guest CTR saved in shadow VCPU SCRATCH2 if RELOCATABLE
* guest R13 saved in SPRN_SCRATCH0
*/
+#ifdef CONFIG_RELOCATABLE
+ ld r9, HSTATE_SCRATCH2(r13)
+ mtctr r9
+#endif
+
lbz r9, HSTATE_IN_GUEST(r13)
cmpwi r9, KVM_GUEST_MODE_HOST_HV
beq kvmppc_bad_host_intr
diff --git a/arch/powerpc/kvm/book3s_segment.S
b/arch/powerpc/kvm/book3s_segment.S
index 3b29f0f..4d25b7b 100644
--- a/arch/powerpc/kvm/book3s_segment.S
+++ b/arch/powerpc/kvm/book3s_segment.S
@@ -177,9 +177,14 @@ kvmppc_interrupt_pr:
* R13 = PACA
* HSTATE.SCRATCH0 = guest R12
* HSTATE.SCRATCH1 = guest R9
+ * HSTATE.SCRATCH2 = guest CTR if RELOCATABLE
*/
#ifdef CONFIG_PPC64
/* Match 32-bit entry */
+#ifdef CONFIG_RELOCATABLE
+ ld r9,HSTATE_SCRATCH2(r13)
+ mtctr r9
+#endif
ld r9,HSTATE_SCRATCH1(r13)
stw r12,HSTATE_SCRATCH1(r13) /* CR is in the low half of r12 */
srdi r12, r12, 32 /* trap is in the high half of r12 */
--
2.10.2
