KVM: PPC: Book3S: 64-bit CONFIG_RELOCATABLE support for interrupts

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 <npiggin@gmail.com>
Acked-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index a02a268..9a5dbfb 100644 (file)
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -97,6 +97,15 @@
        ld      reg,PACAKBASE(r13);                                     \
        ori     reg,reg,(ABS_ADDR(label))@l;
 
+/*
+ * Branches from unrelocated code (e.g., interrupts) to labels outside
+ * head-y require >64K offsets.
+ */
+#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 +236,40 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
        mtctr   reg;                                                    \
        bctr
 
+/*
+ * KVM requires __LOAD_FAR_HANDLER.
+ *
+ * __BRANCH_TO_KVM_EXIT branches are also a special case because they
+ * explicitly use r9 then reload it from PACA before branching. Hence
+ * the double-underscore.
+ */
+#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
+
 #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
+
 #endif
 
+
 #define __KVM_HANDLER(area, h, n)                                      \
        BEGIN_FTR_SECTION_NESTED(947)                                   \
        ld      r10,area+EX_CFAR(r13);                                  \
@@ -246,8 +283,8 @@ 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
+       /* This reloads r9 before branching to kvmppc_interrupt */      \
+       __BRANCH_TO_KVM_EXIT(area, kvmppc_interrupt)
 
 #define __KVM_HANDLER_SKIP(area, h, n)                                 \
        cmpwi   r10,KVM_GUEST_MODE_SKIP;                                \
@@ -260,8 +297,8 @@ 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;                                       \
+       /* This reloads r9 before branching to 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 89b4f12..65a2559 100644 (file)
--- 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
 

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 11882aa..264ac9a 100644 (file)
--- 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 +1152,12 @@ 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)
+       mtctr   r3
+#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 68e4508..2a2b96d 100644 (file)
--- 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 */