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_SCRATCH1 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 | 43 +++++++++++++++++++++++++++++---
arch/powerpc/kernel/exceptions-64s.S | 4 +--
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 11 +++++---
arch/powerpc/kvm/book3s_segment.S | 7 ++++++
4 files changed, 56 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/include/asm/exception-64s.h
b/arch/powerpc/include/asm/exception-64s.h
index a02a268bde6b..e36c741e22d5 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 +232,44 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
mtctr reg; \
bctr
+/*
+ * KVM requires >64K branches when branching from unrelocated code.
+ */
+#define __BRANCH_TO_KVM_EXIT(area, label) \
+ mfctr r9; \
+ std r9,HSTATE_SCRATCH1(r13); \
+ __LOAD_FAR_HANDLER(r9, label); \
+ mtctr r9; \
+ ld r9,area+EX_R9(r13); \
+ 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(area, label) \
+ ld r9,area+EX_R9(r13); \
+ 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); \
@@ -246,8 +283,7 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
std r12,HSTATE_SCRATCH0(r13); \
sldi r12,r9,32; \
ori r12,r12,(n); \
- ld r9,area+EX_R9(r13); \
- b kvmppc_interrupt
+ __BRANCH_TO_KVM_EXIT(area, kvmppc_interrupt)
#define __KVM_HANDLER_SKIP(area, h, n) \
cmpwi r10,KVM_GUEST_MODE_SKIP; \
@@ -260,8 +296,7 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
std r12,HSTATE_SCRATCH0(r13); \
sldi r12,r9,32; \
ori r12,r12,(n); \
- ld r9,area+EX_R9(r13); \
- b kvmppc_interrupt; \
+ __BRANCH_TO_KVM_EXIT(area, kvmppc_interrupt); \
89: mtocrf 0x80,r9; \
ld r9,area+EX_R9(r13); \
ld r10,area+EX_R10(r13); \
diff --git a/arch/powerpc/kernel/exceptions-64s.S
b/arch/powerpc/kernel/exceptions-64s.S
index 89b4f122aec6..d40307cfeb39 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 11882aac8216..c18ce740452b 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1060,15 +1060,16 @@ kvmppc_interrupt_hv:
* R12 = (guest CR << 32) | interrupt vector
* R13 = PACA
* guest R12 saved in shadow VCPU SCRATCH0
+ * guest CTR saved in shadow VCPU SCRATCH1 if RELOCATABLE
* guest R13 saved in SPRN_SCRATCH0
*/
- std r9, HSTATE_SCRATCH1(r13)
+ std r9, HSTATE_SCRATCH2(r13)
lbz r9, HSTATE_IN_GUEST(r13)
cmpwi r9, KVM_GUEST_MODE_HOST_HV
beq kvmppc_bad_host_intr
#ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
cmpwi r9, KVM_GUEST_MODE_GUEST
- ld r9, HSTATE_SCRATCH1(r13)
+ ld r9, HSTATE_SCRATCH2(r13)
beq kvmppc_interrupt_pr
#endif
/* We're now back in the host but in guest MMU context */
@@ -1088,7 +1089,7 @@ kvmppc_interrupt_hv:
std r6, VCPU_GPR(R6)(r9)
std r7, VCPU_GPR(R7)(r9)
std r8, VCPU_GPR(R8)(r9)
- ld r0, HSTATE_SCRATCH1(r13)
+ ld r0, HSTATE_SCRATCH2(r13)
std r0, VCPU_GPR(R9)(r9)
std r10, VCPU_GPR(R10)(r9)
std r11, VCPU_GPR(R11)(r9)
@@ -1151,7 +1152,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
11: stw r3,VCPU_HEIR(r9)
/* these are volatile across C function calls */
+#ifdef CONFIG_RELOCATABLE
+ ld r3, HSTATE_SCRATCH1(r13)
+#else
mfctr r3
+#endif
mfxer r4
std r3, VCPU_CTR(r9)
std r4, VCPU_XER(r9)
diff --git a/arch/powerpc/kvm/book3s_segment.S
b/arch/powerpc/kvm/book3s_segment.S
index 68e45080cf93..2a2b96d53999 100644
--- a/arch/powerpc/kvm/book3s_segment.S
+++ b/arch/powerpc/kvm/book3s_segment.S
@@ -175,9 +175,16 @@ kvmppc_interrupt_pr:
* R12 = (guest CR << 32) | exit handler id
* R13 = PACA
* HSTATE.SCRATCH0 = guest R12
+ * HSTATE.SCRATCH1 = guest CTR if RELOCATABLE
*/
#ifdef CONFIG_PPC64
/* Match 32-bit entry */
+#ifdef CONFIG_RELOCATABLE
+ std r9, HSTATE_SCRATCH2(r13)
+ ld r9, HSTATE_SCRATCH1(r13)
+ mtctr r9
+ ld r9, HSTATE_SCRATCH2(r13)
+#endif
rotldi r12, r12, 32 /* Flip R12 halves for stw */
stw r12, HSTATE_SCRATCH1(r13) /* CR is now in the low half */
srdi r12, r12, 32 /* shift trap into low half */
--
2.11.0
