[PATCH 4.11 25/58] KVM: PPC: Book3S HV: Save/restore host values of debug registers

Greg Kroah-Hartman
2017-06-27T14:27:34Z

From: Paul Mackerras <paulus@ozlabs.org>

commit 7ceaa6dcd8c6f59588428cec37f3c8093dd1011f upstream.

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)
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 45 ++++++++++++++++++++++----------
1 file changed, 32 insertions(+), 13 deletions(-)

--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -43,6 +43,17 @@ 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.
@@ -327,10 +338,10 @@ 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

/*
@@ -553,12 +564,6 @@ 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:

@@ -574,7 +579,7 @@ 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)
@@ -764,6 +769,14 @@ 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 */
@@ -1464,8 +1477,6 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_3
* 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
@@ -1631,6 +1642,14 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)

/* 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)
ld r7, STACK_SLOT_PID(r1)
@@ -1782,8 +1801,8 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_R
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