KVM: PPC: Book3S HV: Save/restore host values of debug registers

At present, HV KVM on POWER8 and POWER9 machines loses any instruction
or data breakpoint set in the host whenever a guest is run.
Instruction breakpoints are currently only used by xmon, but ptrace
and the perf_event subsystem can set data breakpoints as well as xmon.

To fix this, we save the host values of the debug registers (CIABR,
DAWR and DAWRX) before entering the guest and restore them on exit.
To provide space to save them in the stack frame, we expand the stack
frame allocated by kvmppc_hv_entry() from 112 to 144 bytes.

Fixes: b005255e12a3 ("KVM: PPC: Book3S HV: Context-switch new POWER8 SPRs", 2014-01-08)
Cc: stable@vger.kernel.org # v3.14+
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 4e4390564276cbaad9687ac9f7d28bc0fa98a221..4888dd494604f101a194a51ff168c44d85c4354d 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -44,6 +44,17 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_300)
 #define NAPPING_CEDE   1
 #define NAPPING_NOVCPU 2
 
+/* Stack frame offsets for kvmppc_hv_entry */
+#define SFS                    144
+#define STACK_SLOT_TRAP                (SFS-4)
+#define STACK_SLOT_TID         (SFS-16)
+#define STACK_SLOT_PSSCR       (SFS-24)
+#define STACK_SLOT_PID         (SFS-32)
+#define STACK_SLOT_IAMR                (SFS-40)
+#define STACK_SLOT_CIABR       (SFS-48)
+#define STACK_SLOT_DAWR                (SFS-56)
+#define STACK_SLOT_DAWRX       (SFS-64)
+
 /*
  * Call kvmppc_hv_entry in real mode.
  * Must be called with interrupts hard-disabled.
@@ -328,10 +339,10 @@ kvm_novcpu_exit:
        bl      kvmhv_accumulate_time
 #endif
 13:    mr      r3, r12
-       stw     r12, 112-4(r1)
+       stw     r12, STACK_SLOT_TRAP(r1)
        bl      kvmhv_commence_exit
        nop
-       lwz     r12, 112-4(r1)
+       lwz     r12, STACK_SLOT_TRAP(r1)
        b       kvmhv_switch_to_host
 
 /*
@@ -554,12 +565,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
  *                                                                            *
  *****************************************************************************/
 
-/* Stack frame offsets */
-#define STACK_SLOT_TID         (112-16)
-#define STACK_SLOT_PSSCR       (112-24)
-#define STACK_SLOT_PID         (112-32)
-#define STACK_SLOT_IAMR                (112-40)
-
 .global kvmppc_hv_entry
 kvmppc_hv_entry:
 
@@ -575,7 +580,7 @@ kvmppc_hv_entry:
         */
        mflr    r0
        std     r0, PPC_LR_STKOFF(r1)
-       stdu    r1, -112(r1)
+       stdu    r1, -SFS(r1)
 
        /* Save R1 in the PACA */
        std     r1, HSTATE_HOST_R1(r13)
@@ -765,6 +770,14 @@ BEGIN_FTR_SECTION
        std     r7, STACK_SLOT_PID(r1)
        std     r8, STACK_SLOT_IAMR(r1)
 END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
+BEGIN_FTR_SECTION
+       mfspr   r5, SPRN_CIABR
+       mfspr   r6, SPRN_DAWR
+       mfspr   r7, SPRN_DAWRX
+       std     r5, STACK_SLOT_CIABR(r1)
+       std     r6, STACK_SLOT_DAWR(r1)
+       std     r7, STACK_SLOT_DAWRX(r1)
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 
 BEGIN_FTR_SECTION
        /* Set partition DABR */
@@ -1518,8 +1531,6 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300)
         * set by the guest could disrupt the host.
         */
        li      r0, 0
-       mtspr   SPRN_CIABR, r0
-       mtspr   SPRN_DAWRX, r0
        mtspr   SPRN_PSPB, r0
        mtspr   SPRN_WORT, r0
 BEGIN_FTR_SECTION
@@ -1684,6 +1695,14 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
        ptesync
 
        /* Restore host values of some registers */
+BEGIN_FTR_SECTION
+       ld      r5, STACK_SLOT_CIABR(r1)
+       ld      r6, STACK_SLOT_DAWR(r1)
+       ld      r7, STACK_SLOT_DAWRX(r1)
+       mtspr   SPRN_CIABR, r5
+       mtspr   SPRN_DAWR, r6
+       mtspr   SPRN_DAWRX, r7
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 BEGIN_FTR_SECTION
        ld      r5, STACK_SLOT_TID(r1)
        ld      r6, STACK_SLOT_PSSCR(r1)
@@ -1836,8 +1855,8 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX)
        li      r0, KVM_GUEST_MODE_NONE
        stb     r0, HSTATE_IN_GUEST(r13)
 
-       ld      r0, 112+PPC_LR_STKOFF(r1)
-       addi    r1, r1, 112
+       ld      r0, SFS+PPC_LR_STKOFF(r1)
+       addi    r1, r1, SFS
        mtlr    r0
        blr