This adds support for single-stepping the guest. To do this we need to
manipulate the guests PSTATE.SS and MDSCR_EL1.SS bits which we do in the
kvm_arm_setup/clear_debug() so we don't affect the apparent state of the
guest. Additionally while the host is debugging the guest we suppress
the ability of the guest to single-step itself.
Signed-off-by: Alex Bennée <alex.bennee@xxxxxxxxxx>
---
v2
- Move pstate/mdscr manipulation into C
- don't export guest_debug to assembly
- add accessor for saved_debug regs
- tweak save/restore of mdscr_el1
v3
- don't save PC in debug information struct
- rename debug_saved_regs->guest_debug_state
- save whole value, only use bits in restore
- add save/restore_guest-debug_regs helper functions
- simplify commit message for clarity
- rm vcpu_debug_saved_reg access fn
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 064c105..9b3ed6d 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -302,7 +302,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
kvm_arm_set_running_vcpu(NULL);
}
-#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)
+#define KVM_GUESTDBG_VALID_MASK (KVM_GUESTDBG_ENABLE | \
+ KVM_GUESTDBG_USE_SW_BP | \
+ KVM_GUESTDBG_SINGLESTEP)
/**
* kvm_arch_vcpu_ioctl_set_guest_debug - set up guest debugging
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 7cb99b5..b60fa7a 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -123,6 +123,12 @@ struct kvm_vcpu_arch {
* here.
*/
+ /* Guest registers we preserve during guest debugging */
+ struct {
+ u32 pstate;
+ u32 mdscr_el1;
+ } guest_debug_state;
+
/* Don't run the guest */
bool pause;
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 5bee676..19346e8 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -19,11 +19,42 @@
#include <linux/kvm_host.h>
+#include <asm/debug-monitors.h>
+#include <asm/kvm_asm.h>
#include <asm/kvm_arm.h>
+#include <asm/kvm_emulate.h>
+
+/* These are the bits of MDSCR_EL1 we may manipulate */
+#define MDSCR_EL1_DEBUG_MASK (DBG_MDSCR_SS | \
+ DBG_MDSCR_KDE | \
+ DBG_MDSCR_MDE)
+
+#define SPSR_DEBUG_MASK DBG_SPSR_SS
static DEFINE_PER_CPU(u32, mdcr_el2);
/**
+ * save/restore_guest_debug_regs
+ *
+ * For some debug operations we need to tweak some guest registers. As
+ * a result we need to save the state of those registers before we
+ * make those modifications.
+ */
+static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
+{
+ vcpu->arch.guest_debug_state.pstate = *vcpu_cpsr(vcpu);
+ vcpu->arch.guest_debug_state.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1);
+}
+
+static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
+{
+ *vcpu_cpsr(vcpu) |=
+ (vcpu->arch.guest_debug_state.pstate & SPSR_DEBUG_MASK);
+ vcpu_sys_reg(vcpu, MDSCR_EL1) |=
+ (vcpu->arch.guest_debug_state.mdscr_el1 & MDSCR_EL1_DEBUG_MASK);
+}
+
+/**
* kvm_arm_init_debug - grab what we need for debug
*
* Currently the sole task of this function is to retrieve the initial
@@ -38,7 +69,6 @@ void kvm_arm_init_debug(void)
__this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
}
-
/**
* kvm_arm_setup_debug - set up debug related stuff
*
@@ -75,15 +105,37 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
else
vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDA;
- /* Trap breakpoints? */
- if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP)
+ /* Is Guest debugging in effect? */
+ if (vcpu->guest_debug) {
vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
- else
- vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDE;
+ /* Save guest debug state */
+ save_guest_debug_regs(vcpu);
+
+ /*
+ * Single Step (ARM ARM D2.12.3 The software step state
+ * machine)
+ *
+ * If we are doing Single Step we need to manipulate
+ * MDSCR_EL1.SS and PSTATE.SS. If not we need to
+ * suppress the guests ability to trigger single step itself.
+ */
+ if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
+ *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
+ vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_SS;
+ } else {
+ *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
+ vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS;
+ }
+
+ } else {
+ /* Debug operations can go straight to the guest */
+ vcpu->arch.mdcr_el2 &= ~MDCR_EL2_TDE;
+ }
}
void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
{
- /* Nothing to do yet */
+ if (vcpu->guest_debug)
+ restore_guest_debug_regs(vcpu);
}
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 27f38a9..e9de13e 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -103,6 +103,7 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
run->debug.arch.hsr = hsr;
switch (hsr >> ESR_ELx_EC_SHIFT) {
+ case ESR_ELx_EC_SOFTSTP_LOW:
case ESR_ELx_EC_BKPT32:
case ESR_ELx_EC_BRK64:
break;
@@ -130,6 +131,7 @@ static exit_handle_fn arm_exit_handlers[] = {
[ESR_ELx_EC_SYS64] = kvm_handle_sys_reg,
[ESR_ELx_EC_IABT_LOW] = kvm_handle_guest_abort,
[ESR_ELx_EC_DABT_LOW] = kvm_handle_guest_abort,
+ [ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug,
[ESR_ELx_EC_BKPT32] = kvm_handle_guest_debug,
[ESR_ELx_EC_BRK64] = kvm_handle_guest_debug,
};
--
2.3.5
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