On 04.07.14 06:34, Madhavan Srinivasan wrote:
On Thursday 03 July 2014 05:21 PM, Alexander Graf wrote:
On 01.07.14 10:41, Madhavan Srinivasan wrote:
This patch adds kernel side support for software breakpoint.
Design is that, by using an illegal instruction, we trap to hypervisor
via Emulation Assistance interrupt, where we check for the illegal
instruction
and accordingly we return to Host or Guest. Patch also adds support for
software breakpoint in PR KVM.
Patch mandates use of "abs" instruction as sw breakpoint instruction
(primary opcode 31 and extended opcode 360). Based on PowerISA v2.01,
ABS instruction has been dropped from the architecture and treated an
illegal instruction.
Changes v1->v2:
Moved the debug instruction #def to kvm_book3s.h. This way PR_KVM
can also share it.
Added code to use KVM get one reg infrastructure to get debug opcode.
Updated emulate.c to include emulation of debug instruction incase
of PR_KVM.
Made changes to commit message.
Signed-off-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
---
arch/powerpc/include/asm/kvm_book3s.h | 8 ++++++++
arch/powerpc/include/asm/ppc-opcode.h | 5 +++++
arch/powerpc/kvm/book3s.c | 3 ++-
arch/powerpc/kvm/book3s_hv.c | 9 +++++++++
arch/powerpc/kvm/book3s_pr.c | 3 +++
arch/powerpc/kvm/emulate.c | 10 ++++++++++
6 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/kvm_book3s.h
b/arch/powerpc/include/asm/kvm_book3s.h
index f52f656..180d549 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -24,6 +24,14 @@
#include <linux/kvm_host.h>
#include <asm/kvm_book3s_asm.h>
+/*
+ * KVMPPC_INST_BOOK3S_DEBUG is debug Instruction for supporting
Software Breakpoint.
+ * Instruction mnemonic is ABS, primary opcode is 31 and extended
opcode is 360.
+ * Based on PowerISA v2.01, ABS instruction has been dropped from the
architecture
+ * and treated an illegal instruction.
+ */
+#define KVMPPC_INST_BOOK3S_DEBUG 0x7c0002d0
This will still break with LE guests.
I am told to try with all 0s opcode. So rewriting the patch.
The problem with "all 0s" is that it's reasonably likely to occur on
real world code. Hence Segher was proposing something like 0x00dddd00
which should be the same regardless of endianness, but has a certain
appeal of intentional placement ;).
+
struct kvmppc_bat {
u64 raw;
u32 bepi;
diff --git a/arch/powerpc/include/asm/ppc-opcode.h
b/arch/powerpc/include/asm/ppc-opcode.h
index 3132bb9..3fbb4c1 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -111,6 +111,11 @@
#define OP_31_XOP_LHBRX 790
#define OP_31_XOP_STHBRX 918
+/* KVMPPC_INST_BOOK3S_DEBUG -- Software breakpoint Instruction
+ * Instruction mnemonic is ABS, primary opcode is 31 and extended
opcode is 360.
+ */
+#define OP_31_XOP_ABS 360
+
#define OP_LWZ 32
#define OP_LD 58
#define OP_LWZU 33
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index c254c27..b40fe5d 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -789,7 +789,8 @@ int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu
*vcpu,
int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
struct kvm_guest_debug *dbg)
{
- return -EINVAL;
+ vcpu->guest_debug = dbg->control;
+ return 0;
}
void kvmppc_decrementer_func(unsigned long data)
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 7a12edb..402c1ec 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -725,8 +725,14 @@ static int kvmppc_handle_exit_hv(struct kvm_run
*run, struct kvm_vcpu *vcpu,
* we don't emulate any guest instructions at this stage.
*/
case BOOK3S_INTERRUPT_H_EMUL_ASSIST:
+ if (kvmppc_get_last_inst(vcpu) == KVMPPC_INST_BOOK3S_DEBUG ) {
+ run->exit_reason = KVM_EXIT_DEBUG;
+ run->debug.arch.address = kvmppc_get_pc(vcpu);
+ r = RESUME_HOST;
Phew - why can't we just go into the normal instruction emulator for
EMUL_ASSIST?
IIUC, using the emulation_assist_interrupt function (kernel/trap.c) ?
I was more thinking of kvmppc_emulate_instruction() :).
Alex
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