On 11.07.14 10:39, Bharat Bhushan wrote:
This patch emulates debug registers and debug exception
to support guest using debug resource. This enables running
gdb/kgdb etc in guest.
On BOOKE architecture we cannot share debug resources between QEMU and
guest because:
When QEMU is using debug resources then debug exception must
be always enabled. To achieve this we set MSR_DE and also set
MSRP_DEP so guest cannot change MSR_DE.
When emulating debug resource for guest we want guest
to control MSR_DE (enable/disable debug interrupt on need).
So above mentioned two configuration cannot be supported
at the same time. So the result is that we cannot share
debug resources between QEMU and Guest on BOOKE architecture.
In the current design QEMU gets priority over guest, this means that if
QEMU is using debug resources then guest cannot use them and if guest is
using debug resource then QEMU can overwrite them.
Signed-off-by: Bharat Bhushan <Bharat.Bhushan@xxxxxxxxxxxxx>
---
Hi Alex,
I thought of having some print in register emulation if QEMU
is using debug resource, Also when QEMU overwrites guest written
values but that looks excessive. If I uses some variable which
get set when guest starts using debug registers and check in
debug set ioctl then that look ugly. Looking for suggestions
Whatever you do, have QEMU do the print, not the kernel.
arch/powerpc/include/asm/kvm_ppc.h | 3 +
arch/powerpc/kvm/booke.c | 27 +++++++
arch/powerpc/kvm/booke_emulate.c | 157 +++++++++++++++++++++++++++++++++++++
3 files changed, 187 insertions(+)
diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
index e2fd5a1..f3f7611 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -173,6 +173,9 @@ extern int kvmppc_xics_get_xive(struct kvm *kvm, u32 irq, u32 *server,
extern int kvmppc_xics_int_on(struct kvm *kvm, u32 irq);
extern int kvmppc_xics_int_off(struct kvm *kvm, u32 irq);
+void kvmppc_core_dequeue_debug(struct kvm_vcpu *vcpu);
+void kvmppc_core_queue_debug(struct kvm_vcpu *vcpu);
+
union kvmppc_one_reg {
u32 wval;
u64 dval;
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index fadfe76..c2471ed 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -264,6 +264,16 @@ static void kvmppc_core_dequeue_watchdog(struct kvm_vcpu *vcpu)
clear_bit(BOOKE_IRQPRIO_WATCHDOG, &vcpu->arch.pending_exceptions);
}
+void kvmppc_core_queue_debug(struct kvm_vcpu *vcpu)
+{
+ kvmppc_booke_queue_irqprio(vcpu, BOOKE_IRQPRIO_DEBUG);
+}
+
+void kvmppc_core_dequeue_debug(struct kvm_vcpu *vcpu)
+{
+ clear_bit(BOOKE_IRQPRIO_DEBUG, &vcpu->arch.pending_exceptions);
+}
+
static void set_guest_srr(struct kvm_vcpu *vcpu, unsigned long srr0, u32 srr1)
{
#ifdef CONFIG_KVM_BOOKE_HV
@@ -783,6 +793,23 @@ static int kvmppc_handle_debug(struct kvm_run *run, struct kvm_vcpu *vcpu)
struct debug_reg *dbg_reg = &(vcpu->arch.shadow_dbg_reg);
u32 dbsr = vcpu->arch.dbsr;
+ if (vcpu->guest_debug == 0) {
+ /* Debug resources belong to Guest */
+ if (dbsr && (vcpu->arch.shared->msr & MSR_DE))
+ kvmppc_core_queue_debug(vcpu);
+
+ /* Inject a program interrupt if trap debug is not allowed */
+ if ((dbsr & DBSR_TIE) && !(vcpu->arch.shared->msr & MSR_DE))
+ kvmppc_core_queue_program(vcpu, ESR_PTR);
In that case we would've received a program interrupt and never entered
this code path, no?
Alex
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