Re: [PATCH v4] powerpc/kvm: support to handle sw breakpoint

Am 23.08.2014 um 12:17 schrieb Madhavan Srinivasan <maddy@linux.vnet.ibm.c=

om>:

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On Thursday 21 August 2014 02:40 PM, Alexander Graf wrote:
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On 20.08.14 07:52, 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 instr=

uction

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and accordingly we return to Host or Guest. Patch also adds support for
software breakpoint in PR KVM.
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Changes v3->v4:
Made changes to code comments and removed #define of zero opcode
Added a new function to handle the debug instruction emulation in book3s=

_hv

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Rebased the code to latest upstream source.
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Changes v2->v3:
Changed the debug instructions. Using the all zero opcode in the instruc=

tion word

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 as illegal instruction as mentioned in Power ISA instead of ABS
Removed reg updated in emulation assist and added a call to
 kvmppc_emulate_instruction for reg update.
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Changes v1->v2:
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Moved the debug instruction #def to kvm_book3s.h. This way PR_KVM can al=

so share it.

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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.

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Made changes to commit message.
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Signed-off-by: Madhavan Srinivasan <redacted>
---
arch/powerpc/include/asm/kvm_book3s.h |  7 +++++++
arch/powerpc/kvm/book3s.c             |  3 ++-
arch/powerpc/kvm/book3s_hv.c          | 32 +++++++++++++++++++++++++++++=

+--

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arch/powerpc/kvm/book3s_pr.c          |  3 +++
arch/powerpc/kvm/emulate.c            | 11 +++++++++++
5 files changed, 53 insertions(+), 3 deletions(-)
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diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/includ=

e/asm/kvm_book3s.h

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index 6acf0c2..a1944f8 100644

--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h

@@ -24,6 +24,13 @@

#include <linux/kvm_host.h>
#include <asm/kvm_book3s_asm.h>
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+/*
+ * KVMPPC_INST_BOOK3S_DEBUG is debug Instruction for supporting Softwar=

e Breakpoint.

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+ * Based on PowerISA v2.07, Instruction with primary opcode 0 will be t=

reated as illegal

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+ * instruction.
+ */
+#define KVMPPC_INST_BOOK3S_DEBUG    0x00dddd00

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Please change the BookE version of this as well, put the define in a
common header and use a non book specific name.

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I first wanted to get the server side in and then take up this, but i
can do it with this, just concerned incase of booke testing :(

I can test, no problem. You can at least do compile tests on your side alrea=
dy ;)

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+
struct kvmppc_bat {
   u64 raw;
   u32 bepi;

diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index dd03f6b..00e9c9f 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c

@@ -778,7 +778,8 @@ int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *v=

cpu,

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int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
                   struct kvm_guest_debug *dbg)
{
-    return -EINVAL;
+    vcpu->guest_debug =3D dbg->control;
+    return 0;
}
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void kvmppc_decrementer_func(unsigned long data)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c=

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index 27cced9..0a92e45 100644

--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c

@@ -725,6 +725,14 @@ static int kvmppc_hcall_impl_hv(unsigned long cmd)
   return kvmppc_hcall_impl_hv_realmode(cmd);

}
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+static int kvmppc_emulate_debug_instruction_hv(struct kvm_run *run,
+                    struct kvm_vcpu *vcpu)
+{
+    run->exit_reason =3D KVM_EXIT_DEBUG;
+    run->debug.arch.address =3D kvmppc_get_pc(vcpu);
+    return 0;
+}
+
static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *v=

cpu,

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                struct task_struct *tsk)
{

@@ -811,9 +819,26 @@ static int kvmppc_handle_exit_hv(struct kvm_run *ru=

n, struct kvm_vcpu *vcpu,

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    * we don't emulate any guest instructions at this stage.

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This comment is no longer true, it should get changed.

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Will change it.
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    */
   case BOOK3S_INTERRUPT_H_EMUL_ASSIST:
-        kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
-        r =3D RESUME_GUEST;
+    {
+        u32 last_inst;
+        if(kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst) !=3D
+                    EMULATE_DONE) {

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Please only do this if debugging is active.

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Ok sure. But i will add in the else part of the check. Since we do the
instruction check there.

We should only fetch the instruction if sw breakpoint debugging is active.

Alex