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KVM: Improved guest debugging / debug register emulation

PATCH Applied Jan Kiszka 2 participants 7 messages Dec 15, 2008 – Dec 17, 2008

Subsystems (7)
x86 KVM PowerPC s390 +3 more subsystems
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Jan Kiszka

author
#0 lore raw

v3 cover KVM: Improved guest debugging / debug register emulation

This is the kernel part of the guest debugging / debug register emulation patch series.

Changes since last round (was v1, skipped v2 to remain in sync with user space series):
- Reworked patch 3 (single-stepping over STI / MOV SS on VMX)
- Rebased over latest git

Meanwhile basic tests on a SVM host indicate that this platform is fine the series as well.

Find the patches also at git://git.kiszka.org/linux-kvm.git gdb-queue

Jan

--
Siemens AG, Corporate Technology, CT SE 26
Corporate Competence Center Embedded Linux

author
#1 lore raw

PATCH v3 1/5 KVM: VMX: Support for injecting software exceptions

VMX differentiates between processor and software generated exceptions when injecting them into the guest. Extend vmx_queue_exception accordingly (and refactor related constants) so that we can use this service reliably for the new guest debugging framework.

Signed-off-by Jan Kiszka <[email protected]>

---

 arch/x86/include/asm/vmx.h |    3 ++-
 arch/x86/kvm/vmx.c         |   35 ++++++++++++++++++++---------------
 2 files changed, 22 insertions(+), 16 deletions(-)
arch/x86/include/asm/vmx.h +2 -1
index d0238e6..32159f0 100644
@@ -270,8 +270,9 @@ enum vmcs_field {
 
 #define INTR_TYPE_EXT_INTR              (0 << 8) /* external interrupt */
 #define INTR_TYPE_NMI_INTR		(2 << 8) /* NMI */
-#define INTR_TYPE_EXCEPTION             (3 << 8) /* processor exception */
+#define INTR_TYPE_HARD_EXCEPTION	(3 << 8) /* processor exception */
 #define INTR_TYPE_SOFT_INTR             (4 << 8) /* software interrupt */
+#define INTR_TYPE_SOFT_EXCEPTION	(6 << 8) /* software exception */
 
 /* GUEST_INTERRUPTIBILITY_INFO flags. */
 #define GUEST_INTR_STATE_STI		0x00000001
arch/x86/kvm/vmx.c +20 -15
index 6259d74..6592eb1 100644
@@ -189,21 +189,21 @@ static inline int is_page_fault(u32 intr_info)
 {
 	return (intr_info & (INTR_INFO_INTR_TYPE_MASK | INTR_INFO_VECTOR_MASK |
 			     INTR_INFO_VALID_MASK)) ==
-		(INTR_TYPE_EXCEPTION | PF_VECTOR | INTR_INFO_VALID_MASK);
+		(INTR_TYPE_HARD_EXCEPTION | PF_VECTOR | INTR_INFO_VALID_MASK);
 }
 
 static inline int is_no_device(u32 intr_info)
 {
 	return (intr_info & (INTR_INFO_INTR_TYPE_MASK | INTR_INFO_VECTOR_MASK |
 			     INTR_INFO_VALID_MASK)) ==
-		(INTR_TYPE_EXCEPTION | NM_VECTOR | INTR_INFO_VALID_MASK);
+		(INTR_TYPE_HARD_EXCEPTION | NM_VECTOR | INTR_INFO_VALID_MASK);
 }
 
 static inline int is_invalid_opcode(u32 intr_info)
 {
 	return (intr_info & (INTR_INFO_INTR_TYPE_MASK | INTR_INFO_VECTOR_MASK |
 			     INTR_INFO_VALID_MASK)) ==
-		(INTR_TYPE_EXCEPTION | UD_VECTOR | INTR_INFO_VALID_MASK);
+		(INTR_TYPE_HARD_EXCEPTION | UD_VECTOR | INTR_INFO_VALID_MASK);
 }
 
 static inline int is_external_interrupt(u32 intr_info)

@@ -747,29 +747,33 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
 				bool has_error_code, u32 error_code)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	u32 intr_info = nr | INTR_INFO_VALID_MASK;
 
-	if (has_error_code)
+	if (has_error_code) {
 		vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE, error_code);
+		intr_info |= INTR_INFO_DELIVER_CODE_MASK;
+	}
 
 	if (vcpu->arch.rmode.active) {
 		vmx->rmode.irq.pending = true;
 		vmx->rmode.irq.vector = nr;
 		vmx->rmode.irq.rip = kvm_rip_read(vcpu);
-		if (nr == BP_VECTOR)
+		if (nr == BP_VECTOR || nr == OF_VECTOR)
 			vmx->rmode.irq.rip++;
-		vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
-			     nr | INTR_TYPE_SOFT_INTR
-			     | (has_error_code ? INTR_INFO_DELIVER_CODE_MASK : 0)
-			     | INTR_INFO_VALID_MASK);
+		intr_info |= INTR_TYPE_SOFT_INTR;
+		vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info);
 		vmcs_write32(VM_ENTRY_INSTRUCTION_LEN, 1);
 		kvm_rip_write(vcpu, vmx->rmode.irq.rip - 1);
 		return;
 	}
 
-	vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
-		     nr | INTR_TYPE_EXCEPTION
-		     | (has_error_code ? INTR_INFO_DELIVER_CODE_MASK : 0)
-		     | INTR_INFO_VALID_MASK);
+	if (nr == BP_VECTOR || nr == OF_VECTOR) {
+		vmcs_write32(VM_ENTRY_INSTRUCTION_LEN, 1);
+		intr_info |= INTR_TYPE_SOFT_EXCEPTION;
+	} else
+		intr_info |= INTR_TYPE_HARD_EXCEPTION;
+
+	vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info);
 }
 
 static bool vmx_exception_injected(struct kvm_vcpu *vcpu)

@@ -2649,7 +2653,7 @@ static int handle_exception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	}
 
 	if ((intr_info & (INTR_INFO_INTR_TYPE_MASK | INTR_INFO_VECTOR_MASK)) ==
-	    (INTR_TYPE_EXCEPTION | 1)) {
+	    (INTR_TYPE_HARD_EXCEPTION | 1)) {
 		kvm_run->exit_reason = KVM_EXIT_DEBUG;
 		return 0;
 	}

@@ -3237,7 +3241,8 @@ static void vmx_complete_interrupts(struct vcpu_vmx *vmx)
 			vmx->vcpu.arch.nmi_injected = false;
 	}
 	kvm_clear_exception_queue(&vmx->vcpu);
-	if (idtv_info_valid && type == INTR_TYPE_EXCEPTION) {
+	if (idtv_info_valid && (type == INTR_TYPE_HARD_EXCEPTION ||
+				type == INTR_TYPE_SOFT_EXCEPTION)) {
 		if (idt_vectoring_info & VECTORING_INFO_DELIVER_CODE_MASK) {
 			error = vmcs_read32(IDT_VECTORING_ERROR_CODE);
 			kvm_queue_exception_e(&vmx->vcpu, vector, error);
author
#2 lore raw

PATCH v3 2/5 KVM: New guest debug interface

In reply to Jan Kiszka

This rips out the support for KVM_DEBUG_GUEST and introduces a new IOCTL
instead: KVM_SET_GUEST_DEBUG. The IOCTL payload consists of a generic part, controlling the "main switch" and the single-step feature. The arch specific part adds an x86 interface for intercepting both types of debug exceptions separately and re-injecting them when the host was not interested. Moveover, the foundation for guest debugging via debug registers is layed.

To signal breakpoint events properly back to userland, an arch-specific data block is now returned along KVM_EXIT_DEBUG. For x86, the arch block contains the PC, the debug exception, and relevant debug registers to tell debug events properly apart.

The availability of this new interface is signaled by KVM_CAP_SET_GUEST_DEBUG. Empty stubs for not yet supported archs are provided.

Note that both SVM and VTX are supported, but only the latter was tested yet. Based on the experience with all those VTX corner case, I would be fairly surprised if SVM will work out of the box.

Signed-off-by Jan Kiszka <[email protected]>

---

 arch/ia64/include/asm/kvm.h     |    7 +++
 arch/ia64/kvm/kvm-ia64.c        |    4 +-
 arch/powerpc/include/asm/kvm.h  |    7 +++
 arch/powerpc/kvm/powerpc.c      |    4 +-
 arch/s390/include/asm/kvm.h     |    7 +++
 arch/s390/kvm/kvm-s390.c        |    4 +-
 arch/x86/include/asm/kvm.h      |   18 ++++++++
 arch/x86/include/asm/kvm_host.h |    9 ----
 arch/x86/kvm/svm.c              |   50 ++++++++++++++++++++-
 arch/x86/kvm/vmx.c              |   93 +++++++++++++++------------------------
 arch/x86/kvm/x86.c              |   14 +++---
 include/linux/kvm.h             |   51 +++++++++++++++------
 include/linux/kvm_host.h        |    6 +--
 virt/kvm/kvm_main.c             |    6 +--
 14 files changed, 179 insertions(+), 101 deletions(-)
arch/ia64/include/asm/kvm.h +7 -0
index f38472a..c4ab145 100644
@@ -208,4 +208,11 @@ struct kvm_sregs {
 struct kvm_fpu {
 };
 
+struct kvm_debug_exit_arch {
+};
+
+/* for KVM_SET_GUEST_DEBUG */
+struct kvm_guest_debug_arch {
+};
+
 #endif
arch/ia64/kvm/kvm-ia64.c +2 -2
index d2eb969..daa822b 100644
@@ -1315,8 +1315,8 @@ int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
 	return -EINVAL;
 }
 
-int kvm_arch_vcpu_ioctl_debug_guest(struct kvm_vcpu *vcpu,
-		struct kvm_debug_guest *dbg)
+int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
+					struct kvm_guest_debug *dbg)
 {
 	return -EINVAL;
 }
arch/powerpc/include/asm/kvm.h +7 -0
index f993e41..755f1b1 100644
@@ -52,4 +52,11 @@ struct kvm_fpu {
 	__u64 fpr[32];
 };
 
+struct kvm_debug_exit_arch {
+};
+
+/* for KVM_SET_GUEST_DEBUG */
+struct kvm_guest_debug_arch {
+};
+
 #endif /* __LINUX_KVM_POWERPC_H */
arch/powerpc/kvm/powerpc.c +2 -2
index d188618..74b576a 100644
@@ -230,8 +230,8 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 	kvmppc_core_vcpu_put(vcpu);
 }
 
-int kvm_arch_vcpu_ioctl_debug_guest(struct kvm_vcpu *vcpu,
-                                    struct kvm_debug_guest *dbg)
+int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
+					struct kvm_guest_debug *dbg)
 {
 	int i;
arch/s390/include/asm/kvm.h +7 -0
index d74002f..0d56683 100644
@@ -42,4 +42,11 @@ struct kvm_fpu {
 	__u64 fprs[16];
 };
 
+struct kvm_debug_exit_arch {
+};
+
+/* for KVM_SET_GUEST_DEBUG */
+struct kvm_guest_debug_arch {
+};
+
 #endif
arch/s390/kvm/kvm-s390.c +2 -2
index be84971..54b6534 100644
@@ -418,8 +418,8 @@ int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu,
 	return -EINVAL; /* not implemented yet */
 }
 
-int kvm_arch_vcpu_ioctl_debug_guest(struct kvm_vcpu *vcpu,
-				    struct kvm_debug_guest *dbg)
+int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
+					struct kvm_guest_debug *dbg)
 {
 	return -EINVAL; /* not implemented yet */
 }
arch/x86/include/asm/kvm.h +18 -0
index b95162a..4baf107 100644
@@ -205,6 +205,24 @@ struct kvm_pit_channel_state {
 	__s64 count_load_time;
 };
 
+struct kvm_debug_exit_arch {
+	__u32 exception;
+	__u32 pad;
+	__u64 pc;
+	__u64 dr6;
+	__u64 dr7;
+};
+
+#define KVM_GUESTDBG_USE_SW_BP		0x00010000
+#define KVM_GUESTDBG_USE_HW_BP		0x00020000
+#define KVM_GUESTDBG_INJECT_DB		0x00040000
+#define KVM_GUESTDBG_INJECT_BP		0x00080000
+
+/* for KVM_SET_GUEST_DEBUG */
+struct kvm_guest_debug_arch {
+	__u64 debugreg[8];
+};
+
 struct kvm_pit_state {
 	struct kvm_pit_channel_state channels[3];
 };
arch/x86/include/asm/kvm_host.h +1 -8
index 97215a4..8498e63 100644
@@ -134,12 +134,6 @@ enum {
 
 #define KVM_NR_MEM_OBJS 40
 
-struct kvm_guest_debug {
-	int enabled;
-	unsigned long bp[4];
-	int singlestep;
-};
-
 /*
  * We don't want allocation failures within the mmu code, so we preallocate
  * enough memory for a single page fault in a cache.

@@ -446,8 +440,7 @@ struct kvm_x86_ops {
 	void (*vcpu_put)(struct kvm_vcpu *vcpu);
 
 	int (*set_guest_debug)(struct kvm_vcpu *vcpu,
-			       struct kvm_debug_guest *dbg);
-	void (*guest_debug_pre)(struct kvm_vcpu *vcpu);
+			       struct kvm_guest_debug *dbg);
 	int (*get_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata);
 	int (*set_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 data);
 	u64 (*get_segment_base)(struct kvm_vcpu *vcpu, int seg);
arch/x86/kvm/svm.c +48 -2

69 lines not on this page · raw message

arch/x86/kvm/vmx.c +36 -57

145 lines not on this page · raw message

arch/x86/kvm/x86.c +8 -6
index 0e6aa81..6849039 100644
@@ -2976,9 +2976,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 		goto out;
 	}
 
-	if (vcpu->guest_debug.enabled)
-		kvm_x86_ops->guest_debug_pre(vcpu);
-
 	vcpu->guest_mode = 1;
 	/*
 	 * Make sure that guest_mode assignment won't happen after

@@ -3189,7 +3186,7 @@ int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 	/*
 	 * Don't leak debug flags in case they were set for guest debugging
 	 */
-	if (vcpu->guest_debug.enabled && vcpu->guest_debug.singlestep)
+	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
 		regs->rflags &= ~(X86_EFLAGS_TF | X86_EFLAGS_RF);
 
 	vcpu_put(vcpu);

@@ -3808,8 +3805,8 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
-int kvm_arch_vcpu_ioctl_debug_guest(struct kvm_vcpu *vcpu,
-				    struct kvm_debug_guest *dbg)
+int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
+					struct kvm_guest_debug *dbg)
 {
 	int r;
 

@@ -3817,6 +3814,11 @@ int kvm_arch_vcpu_ioctl_debug_guest(struct kvm_vcpu *vcpu,
 
 	r = kvm_x86_ops->set_guest_debug(vcpu, dbg);
 
+	if (dbg->control & KVM_GUESTDBG_INJECT_DB)
+		kvm_queue_exception(vcpu, DB_VECTOR);
+	else if (dbg->control & KVM_GUESTDBG_INJECT_BP)
+		kvm_queue_exception(vcpu, BP_VECTOR);
+
 	vcpu_put(vcpu);
 
 	return r;
include/linux/kvm.h +35 -16

87 lines not on this page · raw message

include/linux/kvm_host.h +3 -3
index eafabd5..d63e9a4 100644
@@ -73,7 +73,7 @@ struct kvm_vcpu {
 	struct kvm_run *run;
 	int guest_mode;
 	unsigned long requests;
-	struct kvm_guest_debug guest_debug;
+	unsigned long guest_debug;
 	int fpu_active;
 	int guest_fpu_loaded;
 	wait_queue_head_t wq;

@@ -255,8 +255,8 @@ int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
 				    struct kvm_mp_state *mp_state);
 int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
 				    struct kvm_mp_state *mp_state);
-int kvm_arch_vcpu_ioctl_debug_guest(struct kvm_vcpu *vcpu,
-				    struct kvm_debug_guest *dbg);
+int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
+					struct kvm_guest_debug *dbg);
 int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run);
 
 int kvm_arch_init(void *opaque);
virt/kvm/kvm_main.c +3 -3
index fc6127c..ffd261d 100644
@@ -1697,13 +1697,13 @@ out_free2:
 		r = 0;
 		break;
 	}
-	case KVM_DEBUG_GUEST: {
-		struct kvm_debug_guest dbg;
+	case KVM_SET_GUEST_DEBUG: {
+		struct kvm_guest_debug dbg;
 
 		r = -EFAULT;
 		if (copy_from_user(&dbg, argp, sizeof dbg))
 			goto out;
-		r = kvm_arch_vcpu_ioctl_debug_guest(vcpu, &dbg);
+		r = kvm_arch_vcpu_ioctl_set_guest_debug(vcpu, &dbg);
 		if (r)
 			goto out;
 		r = 0;
author
#3 lore raw

PATCH v3 3/5 KVM: VMX: Allow single-stepping when uninterruptible

In reply to Jan Kiszka

When single-stepping over STI and MOV SS, we must clear the corresponding interruptibility bits in the guest state. Otherwise vmentry fails as it then expects bit 14 (BS) in pending debug exceptions being set, but that's not correct for the guest debugging case.

Note that clearing those bits is safe as we check for interruptibility based on the original state and do not inject interrupts or NMIs if guest interruptibility was blocked.

Signed-off-by Jan Kiszka <[email protected]>

---

 arch/x86/kvm/vmx.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
arch/x86/kvm/vmx.c +10 -0
index 7d2d6ff..e16d4a6 100644
@@ -2477,6 +2477,11 @@ static void do_interrupt_requests(struct kvm_vcpu *vcpu,
 {
 	vmx_update_window_states(vcpu);
 
+	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
+		vmcs_clear_bits(GUEST_INTERRUPTIBILITY_INFO,
+				GUEST_INTR_STATE_STI |
+				GUEST_INTR_STATE_MOV_SS);
+
 	if (vcpu->arch.nmi_pending && !vcpu->arch.nmi_injected) {
 		if (vcpu->arch.interrupt.pending) {
 			enable_nmi_window(vcpu);

@@ -3243,6 +3248,11 @@ static void vmx_intr_assist(struct kvm_vcpu *vcpu)
 
 	vmx_update_window_states(vcpu);
 
+	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
+		vmcs_clear_bits(GUEST_INTERRUPTIBILITY_INFO,
+				GUEST_INTR_STATE_STI |
+				GUEST_INTR_STATE_MOV_SS);
+
 	if (vcpu->arch.nmi_pending && !vcpu->arch.nmi_injected) {
 		if (vcpu->arch.interrupt.pending) {
 			enable_nmi_window(vcpu);
author
#4 lore raw

PATCH v3 4/5 KVM: x86: Virtualize debug registers

In reply to Jan Kiszka

So far KVM only had basic x86 debug register support, once introduced to realize guest debugging that way. The guest itself was not able to use those registers.

This patch now adds (almost) full support for guest self-debugging via hardware registers. It refactors the code, moving generic parts out of SVM (VMX was already cleaned up by the KVM_SET_GUEST_DEBUG patches), and it ensures that the registers are properly switched between host and guest.

This patch also prepares debug register usage by the host. The latter will (once wired-up by the following patch) allow for hardware breakpoints/watchpoints in guest code. If this is enabled, the guest will only see faked debug registers without functionality, but with content reflecting the guest's modifications.

Tested on Intel only, but SVM /should/ work as well, but who knows...

Known limitations: Trapping on tss switch won't work - most probably on Intel.

Credits also go to Joerg Roedel - I used his once posted debugging series as platform for this patch.

Signed-off-by Jan Kiszka <[email protected]>

---

 arch/x86/include/asm/kvm_host.h |   22 +++++++
 arch/x86/include/asm/vmx.h      |    2 -
 arch/x86/kvm/kvm_svm.h          |    6 --
 arch/x86/kvm/svm.c              |  116 ++++++++++++++-------------------------
 arch/x86/kvm/vmx.c              |  114 +++++++++++++++++++++++++++++++++-----
 arch/x86/kvm/x86.c              |   29 ++++++++++
 6 files changed, 193 insertions(+), 96 deletions(-)
arch/x86/include/asm/kvm_host.h +22 -0
index 8498e63..c83d411 100644
@@ -134,6 +134,19 @@ enum {
 
 #define KVM_NR_MEM_OBJS 40
 
+#define KVM_NR_DB_REGS	4
+
+#define DR6_BD		(1 << 13)
+#define DR6_BS		(1 << 14)
+#define DR6_FIXED_1	0xffff0ff0
+#define DR6_VOLATILE	0x0000e00f
+
+#define DR7_BP_EN_MASK	0x000000ff
+#define DR7_GE		(1 << 9)
+#define DR7_GD		(1 << 13)
+#define DR7_FIXED_1	0x00000400
+#define DR7_VOLATILE	0xffff23ff
+
 /*
  * We don't want allocation failures within the mmu code, so we preallocate
  * enough memory for a single page fault in a cache.

@@ -332,6 +345,15 @@ struct kvm_vcpu_arch {
 
 	struct mtrr_state_type mtrr_state;
 	u32 pat;
+
+	int switch_db_regs;
+	unsigned long host_db[KVM_NR_DB_REGS];
+	unsigned long host_dr6;
+	unsigned long host_dr7;
+	unsigned long db[KVM_NR_DB_REGS];
+	unsigned long dr6;
+	unsigned long dr7;
+	unsigned long eff_db[KVM_NR_DB_REGS];
 };
 
 struct kvm_mem_alias {
arch/x86/include/asm/vmx.h +1 -1
index 32159f0..498f944 100644
@@ -312,7 +312,7 @@ enum vmcs_field {
 #define DEBUG_REG_ACCESS_TYPE           0x10    /* 4, direction of access */
 #define TYPE_MOV_TO_DR                  (0 << 4)
 #define TYPE_MOV_FROM_DR                (1 << 4)
-#define DEBUG_REG_ACCESS_REG            0xf00   /* 11:8, general purpose reg. */
+#define DEBUG_REG_ACCESS_REG(eq)        (((eq) >> 8) & 0xf) /* 11:8, general purpose reg. */
 
 
 /* segment AR */
arch/x86/kvm/kvm_svm.h +0 -6
index 8e5ee99..680f3cc 100644
@@ -18,7 +18,6 @@ static const u32 host_save_user_msrs[] = {
 };
 
 #define NR_HOST_SAVE_USER_MSRS ARRAY_SIZE(host_save_user_msrs)
-#define NUM_DB_REGS 4
 
 struct kvm_vcpu;
 

@@ -29,16 +28,11 @@ struct vcpu_svm {
 	struct svm_cpu_data *svm_data;
 	uint64_t asid_generation;
 
-	unsigned long db_regs[NUM_DB_REGS];
-
 	u64 next_rip;
 
 	u64 host_user_msrs[NR_HOST_SAVE_USER_MSRS];
 	u64 host_gs_base;
 	unsigned long host_cr2;
-	unsigned long host_db_regs[NUM_DB_REGS];
-	unsigned long host_dr6;
-	unsigned long host_dr7;
 
 	u32 *msrpm;
 };
arch/x86/kvm/svm.c +43 -73

188 lines not on this page · raw message

arch/x86/kvm/vmx.c +98 -16

173 lines not on this page · raw message

arch/x86/kvm/x86.c +29 -0
index 6849039..03e5f08 100644
@@ -2996,10 +2996,34 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 
 	kvm_guest_enter();
 
+	get_debugreg(vcpu->arch.host_dr6, 6);
+	get_debugreg(vcpu->arch.host_dr7, 7);
+	if (unlikely(vcpu->arch.switch_db_regs)) {
+		get_debugreg(vcpu->arch.host_db[0], 0);
+		get_debugreg(vcpu->arch.host_db[1], 1);
+		get_debugreg(vcpu->arch.host_db[2], 2);
+		get_debugreg(vcpu->arch.host_db[3], 3);
+
+		set_debugreg(0, 7);
+		set_debugreg(vcpu->arch.eff_db[0], 0);
+		set_debugreg(vcpu->arch.eff_db[1], 1);
+		set_debugreg(vcpu->arch.eff_db[2], 2);
+		set_debugreg(vcpu->arch.eff_db[3], 3);
+	}
 
 	KVMTRACE_0D(VMENTRY, vcpu, entryexit);
 	kvm_x86_ops->run(vcpu, kvm_run);
 
+	if (unlikely(vcpu->arch.switch_db_regs)) {
+		set_debugreg(0, 7);
+		set_debugreg(vcpu->arch.host_db[0], 0);
+		set_debugreg(vcpu->arch.host_db[1], 1);
+		set_debugreg(vcpu->arch.host_db[2], 2);
+		set_debugreg(vcpu->arch.host_db[3], 3);
+	}
+	set_debugreg(vcpu->arch.host_dr6, 6);
+	set_debugreg(vcpu->arch.host_dr7, 7);
+
 	vcpu->guest_mode = 0;
 	local_irq_enable();
 

@@ -4006,6 +4030,11 @@ int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu)
 	vcpu->arch.nmi_pending = false;
 	vcpu->arch.nmi_injected = false;
 
+	vcpu->arch.switch_db_regs = 0;
+	memset(vcpu->arch.db, 0, sizeof(vcpu->arch.db));
+	vcpu->arch.dr6 = DR6_FIXED_1;
+	vcpu->arch.dr7 = DR7_FIXED_1;
+
 	return kvm_x86_ops->vcpu_reset(vcpu);
 }
author
#5 lore raw

PATCH v3 5/5 KVM: x86: Wire-up hardware breakpoints for guest debugging

In reply to Jan Kiszka

Add the remaining bits to make use of debug registers also for guest debugging, thus enabling the use of hardware breakpoints and watchpoints.

Signed-off-by Jan Kiszka <[email protected]>

---

 arch/x86/kvm/svm.c |    5 +++++
 arch/x86/kvm/vmx.c |    5 +++++
 arch/x86/kvm/x86.c |   14 +++++++++++++-
 3 files changed, 23 insertions(+), 1 deletions(-)
arch/x86/kvm/svm.c +5 -0
index 5a7dac4..2d17589 100644
@@ -895,6 +895,11 @@ static int svm_guest_debug(struct kvm_vcpu *vcpu, struct kvm_guest_debug *dbg)
 	} else
 		vcpu->guest_debug = 0;
 
+	if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)
+		svm->vmcb->save.dr7 = dbg->arch.debugreg[7];
+	else
+		svm->vmcb->save.dr7 = vcpu->arch.dr7;
+
 	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
 		svm->vmcb->save.rflags |= X86_EFLAGS_TF | X86_EFLAGS_RF;
 	else if (old_debug & KVM_GUESTDBG_SINGLESTEP)
arch/x86/kvm/vmx.c +5 -0
index 0e8d917..ffd8f24 100644
@@ -1016,6 +1016,11 @@ static int set_guest_debug(struct kvm_vcpu *vcpu, struct kvm_guest_debug *dbg)
 	if (!(vcpu->guest_debug & KVM_GUESTDBG_ENABLE))
 		vcpu->guest_debug = 0;
 
+	if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP)
+		vmcs_writel(GUEST_DR7, dbg->arch.debugreg[7]);
+	else
+		vmcs_writel(GUEST_DR7, vcpu->arch.dr7);
+
 	flags = vmcs_readl(GUEST_RFLAGS);
 	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
 		flags |= X86_EFLAGS_TF | X86_EFLAGS_RF;
arch/x86/kvm/x86.c +13 -1
index 03e5f08..74f58f8 100644
@@ -3832,10 +3832,22 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
 int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 					struct kvm_guest_debug *dbg)
 {
-	int r;
+	int i, r;
 
 	vcpu_load(vcpu);
 
+	if ((dbg->control & (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_HW_BP)) ==
+	    (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_HW_BP)) {
+		for (i = 0; i < KVM_NR_DB_REGS; ++i)
+			vcpu->arch.eff_db[i] = dbg->arch.debugreg[i];
+		vcpu->arch.switch_db_regs =
+			(dbg->arch.debugreg[7] & DR7_BP_EN_MASK);
+	} else {
+		for (i = 0; i < KVM_NR_DB_REGS; i++)
+			vcpu->arch.eff_db[i] = vcpu->arch.db[i];
+		vcpu->arch.switch_db_regs = (vcpu->arch.dr7 & DR7_BP_EN_MASK);
+	}
+
 	r = kvm_x86_ops->set_guest_debug(vcpu, dbg);
 
 	if (dbg->control & KVM_GUESTDBG_INJECT_DB)
Applied
#6 lore raw
In reply to Jan Kiszka
Quoted 12 lines · Jan Kiszka

This is the kernel part of the guest debugging / debug register emulation patch series.

Changes since last round (was v1, skipped v2 to remain in sync with user space series):
- Reworked patch 3 (single-stepping over STI / MOV SS on VMX)
- Rebased over latest git

Meanwhile basic tests on a SVM host indicate that this platform is fine the series as well.

Applied all, thanks.

Signature · 1 line
error compiling committee.c: too many arguments to function