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Re: [Qemu-devel] [PATCH 4/5 v3][RESEND] ppc: Add software breakpoint sup


From: Alexander Graf
Subject: Re: [Qemu-devel] [PATCH 4/5 v3][RESEND] ppc: Add software breakpoint support
Date: Wed, 25 Jun 2014 00:48:09 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.6.0


On 24.06.14 19:59, Madhavan Srinivasan wrote:
On Tuesday 24 June 2014 10:36 PM, address@hidden wrote:

-----Original Message-----
From: Madhavan Srinivasan [mailto:address@hidden
Sent: Tuesday, June 24, 2014 8:59 PM
To: Bhushan Bharat-R65777; address@hidden
Cc: address@hidden; address@hidden
Subject: Re: [PATCH 4/5 v3][RESEND] ppc: Add software breakpoint support

On Tuesday 24 June 2014 05:40 PM, Bharat Bhushan wrote:
This patch allow insert/remove software breakpoint

Signed-off-by: Bharat Bhushan <address@hidden>
---
  target-ppc/kvm.c | 71
+++++++++++++++++++++++++++++++++++++++++++++-----------
  1 file changed, 57 insertions(+), 14 deletions(-)

diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c index
5238de7..8e2dbb3 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -1317,6 +1317,53 @@ static int kvmppc_handle_dcr_write(CPUPPCState *env,
uint32_t dcrn, uint32_t dat
      return 0;
  }

+int kvm_arch_insert_sw_breakpoint(CPUState *cs, struct
+kvm_sw_breakpoint *bp) {
+    /* Mixed endian case is not handled */
+    uint32_t sc = debug_inst_opcode;
+
+    if (cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&bp->saved_insn, 4, 0) ||
+        cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&sc, 4, 1)) {
Instead of hard coding, can we use sizeof ()?
Yes

+        return -EINVAL;
+    }
+
+    return 0;
+}
+
+int kvm_arch_remove_sw_breakpoint(CPUState *cs, struct
+kvm_sw_breakpoint *bp) {
+    uint32_t sc;
+
+    if (cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&sc, 4, 0) ||
+        sc != debug_inst_opcode ||
+        cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&bp->saved_insn, 4, 1)) {
+        return -EINVAL;
+    }
+
Same. Can we use sizeof?
Yes

+    return 0;
+}
+
+void kvm_arch_update_guest_debug(CPUState *cs, struct kvm_guest_debug
+*dbg) {
+    /* Software Breakpoint updates */
+    if (kvm_sw_breakpoints_active(cs)) {
+        dbg->control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP;
+    }
+}
+
+static int kvm_handle_debug(PowerPCCPU *cpu, struct kvm_run *run) {
+    CPUState *cs = CPU(cpu);
+    struct kvm_debug_exit_arch *arch_info = &run->debug.arch;
+    int handle = 0;
+
+    if (kvm_find_sw_breakpoint(cs, arch_info->address)) {
+        handle = 1;
+    }
+
+    return handle;
+}
+
  int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)  {
      PowerPCCPU *cpu = POWERPC_CPU(cs); @@ -1357,6 +1404,16 @@ int
kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
          ret = 0;
          break;

+    case KVM_EXIT_DEBUG:
+        DPRINTF("handle debug exception\n");
+        if (kvm_handle_debug(cpu, run)) {
+            ret = EXCP_DEBUG;
+            break;
+        }
+        /* re-enter, this exception was guest-internal */
Kindly can you explain when this will happen?
If the debug interrupt condition (breakpoint/watchpoint etc) is not set by 
qemu, i.e that is set by guest.

OK. This is my understanding. Kindly correct if it is wrong.
If we are here without any breakpoint from qemu, are we not suppose to
pass it on to guest with an interrupt inject?

Yes. If the guest issued that instruction itself we need to pass in the interrupt that the guest would have received. I think in the book3s case this would be a PROGRAM interrupt rather than a DEBUG interrupt.


Alex




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