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-rw-r--r--arch/arm64/include/asm/kvm_host.h24
-rw-r--r--arch/arm64/kvm/arm.c4
-rw-r--r--arch/arm64/kvm/debug.c145
-rw-r--r--arch/arm64/kvm/guest.c2
-rw-r--r--arch/arm64/kvm/handle_exit.c2
5 files changed, 48 insertions, 129 deletions
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e7036096d9c2..d48516de778d 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -764,17 +764,6 @@ struct kvm_vcpu_arch {
struct arch_timer_cpu timer_cpu;
struct kvm_pmu pmu;
- /*
- * Guest registers we preserve during guest debugging.
- *
- * These shadow registers are updated by the kvm_handle_sys_reg
- * trap handler if the guest accesses or updates them while we
- * are using guest debug.
- */
- struct {
- bool pstate_ss;
- } guest_debug_preserved;
-
/* vcpu power state */
struct kvm_mp_state mp_state;
spinlock_t mp_state_lock;
@@ -924,12 +913,14 @@ struct kvm_vcpu_arch {
#define IN_WFIT __vcpu_single_flag(sflags, BIT(1))
/* vcpu system registers loaded on physical CPU */
#define SYSREGS_ON_CPU __vcpu_single_flag(sflags, BIT(2))
-/* Software step state is Active-pending */
-#define DBG_SS_ACTIVE_PENDING __vcpu_single_flag(sflags, BIT(3))
+/* Software step state is Active-pending for external debug */
+#define HOST_SS_ACTIVE_PENDING __vcpu_single_flag(sflags, BIT(3))
+/* Software step state is Active pending for guest debug */
+#define GUEST_SS_ACTIVE_PENDING __vcpu_single_flag(sflags, BIT(4))
/* PMUSERENR for the guest EL0 is on physical CPU */
-#define PMUSERENR_ON_CPU __vcpu_single_flag(sflags, BIT(4))
+#define PMUSERENR_ON_CPU __vcpu_single_flag(sflags, BIT(5))
/* WFI instruction trapped */
-#define IN_WFI __vcpu_single_flag(sflags, BIT(5))
+#define IN_WFI __vcpu_single_flag(sflags, BIT(6))
/* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
@@ -1341,9 +1332,8 @@ static inline bool kvm_system_needs_idmapped_vectors(void)
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
void kvm_init_host_debug_data(void);
-void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
-void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu);
+void kvm_vcpu_put_debug(struct kvm_vcpu *vcpu);
void kvm_debug_set_guest_ownership(struct kvm_vcpu *vcpu);
void kvm_debug_handle_oslar(struct kvm_vcpu *vcpu, u64 val);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index ec581aeb41f9..563cd0b626b9 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -622,6 +622,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
+ kvm_vcpu_put_debug(vcpu);
kvm_arch_vcpu_put_fp(vcpu);
if (has_vhe())
kvm_vcpu_put_vhe(vcpu);
@@ -1181,7 +1182,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
continue;
}
- kvm_arm_setup_debug(vcpu);
kvm_arch_vcpu_ctxflush_fp(vcpu);
/**************************************************************
@@ -1198,8 +1198,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
* Back from guest
*************************************************************/
- kvm_arm_clear_debug(vcpu);
-
/*
* We must sync the PMU state before the vgic state so
* that the vgic can properly sample the updated state of the
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index db3d74e63bc3..7d3c71d65518 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -3,7 +3,8 @@
* Debug and Guest Debug support
*
* Copyright (C) 2015 - Linaro Ltd
- * Author: Alex Bennée <alex.bennee@linaro.org>
+ * Authors: Alex Bennée <alex.bennee@linaro.org>
+ * Oliver Upton <oliver.upton@linux.dev>
*/
#include <linux/kvm_host.h>
@@ -14,35 +15,6 @@
#include <asm/kvm_arm.h>
#include <asm/kvm_emulate.h>
-
-/*
- * 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.
- *
- * Guest access to MDSCR_EL1 is trapped by the hypervisor and handled
- * after we have restored the preserved value to the main context.
- *
- * When single-step is enabled by userspace, we tweak PSTATE.SS on every
- * guest entry. Preserve PSTATE.SS so we can restore the original value
- * for the vcpu after the single-step is disabled.
- */
-static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
-{
- vcpu->arch.guest_debug_preserved.pstate_ss =
- (*vcpu_cpsr(vcpu) & DBG_SPSR_SS);
-}
-
-static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
-{
- if (vcpu->arch.guest_debug_preserved.pstate_ss)
- *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
- else
- *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
-}
-
/**
* kvm_arm_setup_mdcr_el2 - configure vcpu mdcr_el2 value
*
@@ -91,83 +63,6 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
preempt_enable();
}
-/**
- * kvm_arm_setup_debug - set up debug related stuff
- *
- * @vcpu: the vcpu pointer
- *
- * This is called before each entry into the hypervisor to setup any
- * debug related registers.
- *
- * Additionally, KVM only traps guest accesses to the debug registers if
- * the guest is not actively using them. Since the guest must not interfere
- * with the hardware state when debugging the guest, we must ensure that
- * trapping is enabled whenever we are debugging the guest using the
- * debug registers.
- */
-
-void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
-{
- /* Check if we need to use the debug registers. */
- if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
- /* 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
- * the guest's MDSCR_EL1.SS and PSTATE.SS. Once the
- * step has occurred the hypervisor will trap the
- * debug exception and we return to userspace.
- *
- * If the guest attempts to single step its userspace
- * we would have to deal with a trapped exception
- * while in the guest kernel. Because this would be
- * hard to unwind we suppress the guest's ability to
- * do so by masking MDSCR_EL.SS.
- *
- * This confuses guest debuggers which use
- * single-step behind the scenes but everything
- * returns to normal once the host is no longer
- * debugging the system.
- */
- if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
- /*
- * If the software step state at the last guest exit
- * was Active-pending, we don't set DBG_SPSR_SS so
- * that the state is maintained (to not run another
- * single-step until the pending Software Step
- * exception is taken).
- */
- if (!vcpu_get_flag(vcpu, DBG_SS_ACTIVE_PENDING))
- *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
- else
- *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
- }
- }
-}
-
-void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
-{
- /*
- * Restore the guest's debug registers if we were using them.
- */
- if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
- if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
- if (!(*vcpu_cpsr(vcpu) & DBG_SPSR_SS))
- /*
- * Mark the vcpu as ACTIVE_PENDING
- * until Software Step exception is taken.
- */
- vcpu_set_flag(vcpu, DBG_SS_ACTIVE_PENDING);
- }
-
- restore_guest_debug_regs(vcpu);
- }
-}
-
void kvm_init_host_debug_data(void)
{
u64 dfr0 = read_sysreg(id_aa64dfr0_el1);
@@ -246,6 +141,22 @@ void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu)
if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
vcpu->arch.debug_owner = VCPU_DEBUG_HOST_OWNED;
setup_external_mdscr(vcpu);
+
+ /*
+ * Steal the guest's single-step state machine if userspace wants
+ * single-step the guest.
+ */
+ if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
+ if (*vcpu_cpsr(vcpu) & DBG_SPSR_SS)
+ vcpu_clear_flag(vcpu, GUEST_SS_ACTIVE_PENDING);
+ else
+ vcpu_set_flag(vcpu, GUEST_SS_ACTIVE_PENDING);
+
+ if (!vcpu_get_flag(vcpu, HOST_SS_ACTIVE_PENDING))
+ *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
+ else
+ *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
+ }
} else {
mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
@@ -258,6 +169,26 @@ void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu)
kvm_arm_setup_mdcr_el2(vcpu);
}
+void kvm_vcpu_put_debug(struct kvm_vcpu *vcpu)
+{
+ if (likely(!(vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)))
+ return;
+
+ /*
+ * Save the host's software step state and restore the guest's before
+ * potentially returning to userspace.
+ */
+ if (!(*vcpu_cpsr(vcpu) & DBG_SPSR_SS))
+ vcpu_set_flag(vcpu, HOST_SS_ACTIVE_PENDING);
+ else
+ vcpu_clear_flag(vcpu, HOST_SS_ACTIVE_PENDING);
+
+ if (vcpu_get_flag(vcpu, GUEST_SS_ACTIVE_PENDING))
+ *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
+ else
+ *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
+}
+
/*
* Updates ownership of the debug registers after a trapped guest access to a
* breakpoint/watchpoint register. Host ownership of the debug registers is of
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 1fe097c67766..2196979a24a3 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -924,7 +924,7 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
vcpu->guest_debug = 0;
- vcpu_clear_flag(vcpu, DBG_SS_ACTIVE_PENDING);
+ vcpu_clear_flag(vcpu, HOST_SS_ACTIVE_PENDING);
return 0;
}
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index d7c2990e7c9e..1e302f0c8903 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -193,7 +193,7 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu)
run->debug.arch.far = vcpu->arch.fault.far_el2;
break;
case ESR_ELx_EC_SOFTSTP_LOW:
- vcpu_clear_flag(vcpu, DBG_SS_ACTIVE_PENDING);
+ *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
break;
}
generated by cgit v1.2.3 (git 2.46.0) at 2025-08-01 12:52:36 +0000