From: Nicușor Cîțu <ncitu@xxxxxxxxxxxxxxx>
This would be used either if the introspection tool request it as a
reply to a KVMI_EVENT_PF event or to cope with instructions that cannot
be handled by the x86 emulator during the handling of a VMEXIT. In
these situations, all other vCPU-s are kicked and held, the EPT-based
protection is removed and the guest is single stepped by the vCPU that
triggered the initial VMEXIT. Upon completion the EPT-base protection
is reinstalled and all vCPU-s all allowed to return to the guest.
This is a rather slow workaround that kicks in occasionally. In the
future, the most frequently single-stepped instructions should be added
to the emulator (usually, stores to and from memory - SSE/AVX).
For the moment it works only on Intel.
CC: Jim Mattson <jmattson@xxxxxxxxxx>
CC: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
CC: Joerg Roedel <joro@xxxxxxxxxx>
Signed-off-by: Nicușor Cîțu <ncitu@xxxxxxxxxxxxxxx>
Co-developed-by: Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>
Signed-off-by: Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>
Co-developed-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 3 +
arch/x86/kvm/kvmi.c | 47 ++++++++++-
arch/x86/kvm/svm.c | 5 ++
arch/x86/kvm/vmx/vmx.c | 17 ++++
arch/x86/kvm/x86.c | 19 +++++
include/linux/kvmi.h | 4 +
virt/kvm/kvmi.c | 145 +++++++++++++++++++++++++++++++-
virt/kvm/kvmi_int.h | 16 ++++
8 files changed, 253 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index ad36a5fc2048..60e2c298d469 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1016,6 +1016,7 @@ struct kvm_x86_ops {
void (*msr_intercept)(struct kvm_vcpu *vcpu, unsigned int msr,
bool enable);
bool (*desc_intercept)(struct kvm_vcpu *vcpu, bool enable);
+ void (*set_mtf)(struct kvm_vcpu *vcpu, bool enable);
void (*cr3_write_exiting)(struct kvm_vcpu *vcpu, bool enable);
bool (*nested_pagefault)(struct kvm_vcpu *vcpu);
bool (*spt_fault)(struct kvm_vcpu *vcpu);
@@ -1628,6 +1629,8 @@ void kvm_arch_msr_intercept(struct kvm_vcpu *vcpu, unsigned int msr,
bool enable);
bool kvm_mmu_nested_pagefault(struct kvm_vcpu *vcpu);
bool kvm_spt_fault(struct kvm_vcpu *vcpu);
+void kvm_set_mtf(struct kvm_vcpu *vcpu, bool enable);
+void kvm_set_interrupt_shadow(struct kvm_vcpu *vcpu, int mask);
void kvm_control_cr3_write_exiting(struct kvm_vcpu *vcpu, bool enable);
#endif /* _ASM_X86_KVM_HOST_H */
diff --git a/arch/x86/kvm/kvmi.c b/arch/x86/kvm/kvmi.c
index 04cac5b8a4d0..f0ab4bd9eb37 100644
--- a/arch/x86/kvm/kvmi.c
+++ b/arch/x86/kvm/kvmi.c
@@ -520,7 +520,6 @@ bool kvmi_arch_pf_event(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
u32 ctx_size;
u64 ctx_addr;
u32 action;
- bool singlestep_ignored;
bool ret = false;
if (!kvm_spt_fault(vcpu))
@@ -533,7 +532,7 @@ bool kvmi_arch_pf_event(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
if (ivcpu->effective_rep_complete)
return true;
- action = kvmi_msg_send_pf(vcpu, gpa, gva, access, &singlestep_ignored,
+ action = kvmi_msg_send_pf(vcpu, gpa, gva, access, &ivcpu->ss_requested,
&ivcpu->rep_complete, &ctx_addr,
ivcpu->ctx_data, &ctx_size);
@@ -547,6 +546,8 @@ bool kvmi_arch_pf_event(struct kvm_vcpu *vcpu, gpa_t gpa, gva_t gva,
ret = true;
break;
case KVMI_EVENT_ACTION_RETRY:
+ if (ivcpu->ss_requested && !kvmi_start_ss(vcpu, gpa, access))
+ ret = true;
break;
default:
kvmi_handle_common_event_actions(vcpu, action, "PF");
@@ -758,6 +759,48 @@ int kvmi_arch_cmd_control_cr(struct kvm_vcpu *vcpu,
return 0;
}
+void kvmi_arch_start_single_step(struct kvm_vcpu *vcpu)
+{
+ kvm_set_mtf(vcpu, true);
+
+ /*
+ * Set block by STI only if the RFLAGS.IF = 1.
+ * Blocking by both STI and MOV/POP SS is not possible.
+ */
+ if (kvm_arch_interrupt_allowed(vcpu))
+ kvm_set_interrupt_shadow(vcpu, KVM_X86_SHADOW_INT_STI);
+
+}
+
+void kvmi_arch_stop_single_step(struct kvm_vcpu *vcpu)
+{
+ kvm_set_mtf(vcpu, false);
+ /*
+ * The blocking by STI is cleared after the guest
+ * executes one instruction or incurs an exception.
+ * However we migh stop the SS before entering to guest,
+ * so be sure we are clearing the STI blocking.
+ */
+ kvm_set_interrupt_shadow(vcpu, 0);
+}
+
+u8 kvmi_arch_relax_page_access(u8 old, u8 new)
+{
+ u8 ret = old | new;
+
+ /*
+ * An SPTE entry with just the -wx bits set can trigger a
+ * misconfiguration error from the hardware, as it's the case
+ * for x86 where this access mode is used to mark I/O memory.
+ * Thus, we make sure that -wx accesses are translated to rwx.
+ */
+ if ((ret & (KVMI_PAGE_ACCESS_W | KVMI_PAGE_ACCESS_X)) ==
+ (KVMI_PAGE_ACCESS_W | KVMI_PAGE_ACCESS_X))
+ ret |= KVMI_PAGE_ACCESS_R;
+
+ return ret;
+}
+
static const struct {
unsigned int allow_bit;
enum kvm_page_track_mode track_mode;
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index b178b8900660..3481c0247680 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7183,6 +7183,10 @@ static bool svm_spt_fault(struct kvm_vcpu *vcpu)
return (svm->vmcb->control.exit_code == SVM_EXIT_NPF);
}
+static void svm_set_mtf(struct kvm_vcpu *vcpu, bool enable)
+{
+}
+
static void svm_cr3_write_exiting(struct kvm_vcpu *vcpu, bool enable)
{
}
@@ -7225,6 +7229,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
.cpu_has_accelerated_tpr = svm_cpu_has_accelerated_tpr,
.has_emulated_msr = svm_has_emulated_msr,
+ .set_mtf = svm_set_mtf,
.cr3_write_exiting = svm_cr3_write_exiting,
.msr_intercept = svm_msr_intercept,
.desc_intercept = svm_desc_intercept,
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 7d1e341b51ad..f0369d0574dc 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5384,6 +5384,7 @@ static int handle_invalid_op(struct kvm_vcpu *vcpu)
static int handle_monitor_trap(struct kvm_vcpu *vcpu)
{
+ kvmi_stop_ss(vcpu);
return 1;
}
@@ -5992,6 +5993,11 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
}
}
+ if (kvmi_vcpu_enabled_ss(vcpu)
+ && exit_reason != EXIT_REASON_EPT_VIOLATION
+ && exit_reason != EXIT_REASON_MONITOR_TRAP_FLAG)
+ kvmi_stop_ss(vcpu);
+
if (exit_reason < kvm_vmx_max_exit_handlers
&& kvm_vmx_exit_handlers[exit_reason])
return kvm_vmx_exit_handlers[exit_reason](vcpu);
@@ -7842,6 +7848,16 @@ static __exit void hardware_unsetup(void)
free_kvm_area();
}
+static void vmx_set_mtf(struct kvm_vcpu *vcpu, bool enable)
+{
+ if (enable)
+ vmcs_set_bits(CPU_BASED_VM_EXEC_CONTROL,
+ CPU_BASED_MONITOR_TRAP_FLAG);
+ else
+ vmcs_clear_bits(CPU_BASED_VM_EXEC_CONTROL,
+ CPU_BASED_MONITOR_TRAP_FLAG);
+}
+
static void vmx_msr_intercept(struct kvm_vcpu *vcpu, unsigned int msr,
bool enable)
{
@@ -7927,6 +7943,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
.cpu_has_accelerated_tpr = report_flexpriority,
.has_emulated_msr = vmx_has_emulated_msr,
+ .set_mtf = vmx_set_mtf,
.msr_intercept = vmx_msr_intercept,
.cr3_write_exiting = vmx_cr3_write_exiting,
.desc_intercept = vmx_desc_intercept,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 38aaddadb93a..65855340249a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7358,6 +7358,13 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win)
{
int r;
+ if (kvmi_vcpu_enabled_ss(vcpu))
+ /*
+ * We cannot inject events during single-stepping.
+ * Try again later.
+ */
+ return -1;
+
/* try to reinject previous events if any */
if (vcpu->arch.exception.injected)
@@ -10134,6 +10141,18 @@ void kvm_control_cr3_write_exiting(struct kvm_vcpu *vcpu, bool enable)
}
EXPORT_SYMBOL(kvm_control_cr3_write_exiting);
+void kvm_set_mtf(struct kvm_vcpu *vcpu, bool enable)
+{
+ kvm_x86_ops->set_mtf(vcpu, enable);
+}
+EXPORT_SYMBOL(kvm_set_mtf);
+
+void kvm_set_interrupt_shadow(struct kvm_vcpu *vcpu, int mask)
+{
+ kvm_x86_ops->set_interrupt_shadow(vcpu, mask);
+}
+EXPORT_SYMBOL(kvm_set_interrupt_shadow);
+
bool kvm_spt_fault(struct kvm_vcpu *vcpu)
{
return kvm_x86_ops->spt_fault(vcpu);
diff --git a/include/linux/kvmi.h b/include/linux/kvmi.h
index 5d162b9e67f2..1dc90284dc3a 100644
--- a/include/linux/kvmi.h
+++ b/include/linux/kvmi.h
@@ -22,6 +22,8 @@ bool kvmi_queue_exception(struct kvm_vcpu *vcpu);
void kvmi_trap_event(struct kvm_vcpu *vcpu);
bool kvmi_descriptor_event(struct kvm_vcpu *vcpu, u8 descriptor, u8 write);
void kvmi_handle_requests(struct kvm_vcpu *vcpu);
+void kvmi_stop_ss(struct kvm_vcpu *vcpu);
+bool kvmi_vcpu_enabled_ss(struct kvm_vcpu *vcpu);
void kvmi_init_emulate(struct kvm_vcpu *vcpu);
void kvmi_activate_rep_complete(struct kvm_vcpu *vcpu);
bool kvmi_bp_intercepted(struct kvm_vcpu *vcpu, u32 dbg);
@@ -44,6 +46,8 @@ static inline void kvmi_handle_requests(struct kvm_vcpu *vcpu) { }
static inline bool kvmi_hypercall_event(struct kvm_vcpu *vcpu) { return false; }
static inline bool kvmi_queue_exception(struct kvm_vcpu *vcpu) { return true; }
static inline void kvmi_trap_event(struct kvm_vcpu *vcpu) { }
+static inline void kvmi_stop_ss(struct kvm_vcpu *vcpu) { }
+static inline bool kvmi_vcpu_enabled_ss(struct kvm_vcpu *vcpu) { return false; }
static inline void kvmi_init_emulate(struct kvm_vcpu *vcpu) { }
static inline void kvmi_activate_rep_complete(struct kvm_vcpu *vcpu) { }
static inline bool kvmi_bp_intercepted(struct kvm_vcpu *vcpu, u32 dbg)
diff --git a/virt/kvm/kvmi.c b/virt/kvm/kvmi.c
index d47a725a4045..a3a5af9080a9 100644
--- a/virt/kvm/kvmi.c
+++ b/virt/kvm/kvmi.c
@@ -1260,11 +1260,19 @@ void kvmi_run_jobs(struct kvm_vcpu *vcpu)
}
}
+static bool need_to_wait_for_ss(struct kvm_vcpu *vcpu)
+{
+ struct kvmi_vcpu *ivcpu = IVCPU(vcpu);
+ struct kvmi *ikvm = IKVM(vcpu->kvm);
+
+ return atomic_read(&ikvm->ss_active) && !ivcpu->ss_owner;
+}
+
static bool need_to_wait(struct kvm_vcpu *vcpu)
{
struct kvmi_vcpu *ivcpu = IVCPU(vcpu);
- return ivcpu->reply_waiting;
+ return ivcpu->reply_waiting || need_to_wait_for_ss(vcpu);
}
static bool done_waiting(struct kvm_vcpu *vcpu)
@@ -1572,6 +1580,141 @@ int kvmi_cmd_pause_vcpu(struct kvm_vcpu *vcpu, bool wait)
return 0;
}
+void kvmi_stop_ss(struct kvm_vcpu *vcpu)
+{
+ struct kvmi_vcpu *ivcpu = IVCPU(vcpu);
+ struct kvm *kvm = vcpu->kvm;
+ struct kvmi *ikvm;
+ int i;
+
+ ikvm = kvmi_get(kvm);
+ if (!ikvm)
+ return;
+
+ if (unlikely(!ivcpu->ss_owner)) {
+ kvmi_warn(ikvm, "%s\n", __func__);
+ goto out;
+ }
+
+ for (i = ikvm->ss_level; i--;)
+ kvmi_set_gfn_access(kvm,
+ ikvm->ss_context[i].gfn,
+ ikvm->ss_context[i].old_access,
+ ikvm->ss_context[i].old_write_bitmap);
+
+ ikvm->ss_level = 0;
+
+ kvmi_arch_stop_single_step(vcpu);
+
+ atomic_set(&ikvm->ss_active, false);
+ /*
+ * Make ss_active update visible
+ * before resuming all the other vCPUs.
+ */
+ smp_mb__after_atomic();
+ kvm_make_all_cpus_request(kvm, 0);
+
+ ivcpu->ss_owner = false;
+
+out:
+ kvmi_put(kvm);
+}
+EXPORT_SYMBOL(kvmi_stop_ss);
+
+static bool kvmi_acquire_ss(struct kvm_vcpu *vcpu)
+{
+ struct kvmi_vcpu *ivcpu = IVCPU(vcpu);
+ struct kvmi *ikvm = IKVM(vcpu->kvm);
+
+ if (ivcpu->ss_owner)
+ return true;
+
+ if (atomic_cmpxchg(&ikvm->ss_active, false, true) != false)
+ return false;
+
+ kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_INTROSPECTION |
+ KVM_REQUEST_WAIT);
+
+ ivcpu->ss_owner = true;
+
+ return true;
+}
+
+static bool kvmi_run_ss(struct kvm_vcpu *vcpu, gpa_t gpa, u8 access)
+{
+ struct kvmi *ikvm = IKVM(vcpu->kvm);
+ u8 old_access, new_access;
+ u32 old_write_bitmap;
+ gfn_t gfn = gpa_to_gfn(gpa);
+ int err;
+
+ kvmi_arch_start_single_step(vcpu);
+
+ err = kvmi_get_gfn_access(ikvm, gfn, &old_access, &old_write_bitmap);
+ /* likely was removed from radix tree due to rwx */
+ if (err) {
+ kvmi_warn(ikvm, "%s: gfn 0x%llx not found in the radix tree\n",
+ __func__, gfn);
+ return true;
+ }
+
+ if (ikvm->ss_level == SINGLE_STEP_MAX_DEPTH - 1) {
+ kvmi_err(ikvm, "single step limit reached\n");
+ return false;
+ }
+
+ ikvm->ss_context[ikvm->ss_level].gfn = gfn;
+ ikvm->ss_context[ikvm->ss_level].old_access = old_access;
+ ikvm->ss_context[ikvm->ss_level].old_write_bitmap = old_write_bitmap;
+ ikvm->ss_level++;
+
+ new_access = kvmi_arch_relax_page_access(old_access, access);
+
+ kvmi_set_gfn_access(vcpu->kvm, gfn, new_access, old_write_bitmap);
+
+ return true;
+}
+
+bool kvmi_start_ss(struct kvm_vcpu *vcpu, gpa_t gpa, u8 access)
+{
+ bool ret = false;
+
+ while (!kvmi_acquire_ss(vcpu)) {
+ int err = kvmi_run_jobs_and_wait(vcpu);
+
+ if (err) {
+ kvmi_err(IKVM(vcpu->kvm), "kvmi_acquire_ss() has failed\n");
+ goto out;
+ }
+ }
+
+ if (kvmi_run_ss(vcpu, gpa, access))
+ ret = true;
+ else
+ kvmi_stop_ss(vcpu);
+
+out:
+ return ret;
+}
+
+bool kvmi_vcpu_enabled_ss(struct kvm_vcpu *vcpu)
+{
+ struct kvmi_vcpu *ivcpu = IVCPU(vcpu);
+ struct kvmi *ikvm;
+ bool ret;
+
+ ikvm = kvmi_get(vcpu->kvm);
+ if (!ikvm)
+ return false;
+
+ ret = ivcpu->ss_owner;
+
+ kvmi_put(vcpu->kvm);
+
+ return ret;
+}
+EXPORT_SYMBOL(kvmi_vcpu_enabled_ss);
+
static void kvmi_job_abort(struct kvm_vcpu *vcpu, void *ctx)
{
struct kvmi_vcpu *ivcpu = IVCPU(vcpu);
diff --git a/virt/kvm/kvmi_int.h b/virt/kvm/kvmi_int.h
index d7f9858d3e97..1550fe33ed48 100644
--- a/virt/kvm/kvmi_int.h
+++ b/virt/kvm/kvmi_int.h
@@ -126,6 +126,9 @@ struct kvmi_vcpu {
DECLARE_BITMAP(high, KVMI_NUM_MSR);
} msr_mask;
+ bool ss_owner;
+ bool ss_requested;
+
struct list_head job_list;
spinlock_t job_lock;
@@ -151,6 +154,15 @@ struct kvmi {
DECLARE_BITMAP(event_allow_mask, KVMI_NUM_EVENTS);
DECLARE_BITMAP(vm_ev_mask, KVMI_NUM_EVENTS);
+#define SINGLE_STEP_MAX_DEPTH 8
+ struct {
+ gfn_t gfn;
+ u8 old_access;
+ u32 old_write_bitmap;
+ } ss_context[SINGLE_STEP_MAX_DEPTH];
+ u8 ss_level;
+ atomic_t ss_active;
+
struct {
bool initialized;
atomic_t enabled;
@@ -224,6 +236,7 @@ int kvmi_add_job(struct kvm_vcpu *vcpu,
void *ctx, void (*free_fct)(void *ctx));
void kvmi_handle_common_event_actions(struct kvm_vcpu *vcpu, u32 action,
const char *str);
+bool kvmi_start_ss(struct kvm_vcpu *vcpu, gpa_t gpa, u8 access);
/* arch */
void kvmi_arch_update_page_tracking(struct kvm *kvm,
@@ -274,6 +287,9 @@ int kvmi_arch_cmd_inject_exception(struct kvm_vcpu *vcpu, u8 vector,
u64 address);
int kvmi_arch_cmd_control_cr(struct kvm_vcpu *vcpu,
const struct kvmi_control_cr *req);
+void kvmi_arch_start_single_step(struct kvm_vcpu *vcpu);
+void kvmi_arch_stop_single_step(struct kvm_vcpu *vcpu);
+u8 kvmi_arch_relax_page_access(u8 old, u8 new);
int kvmi_arch_cmd_control_msr(struct kvm_vcpu *vcpu,
const struct kvmi_control_msr *req);
int kvmi_arch_cmd_get_mtrr_type(struct kvm_vcpu *vcpu, u64 gpa, u8 *type);
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