[RFC PATCH v2 03/19] KVM: x86: Add notifications for Heki policy configuration and violation
From: Mickaël Salaün
Date: Sun Nov 12 2023 - 21:24:25 EST
Add an interface for user space to be notified about guests' Heki policy
and related violations.
Extend the KVM_ENABLE_CAP IOCTL with KVM_CAP_HEKI_CONFIGURE and
KVM_CAP_HEKI_DENIAL. Each one takes a bitmask as first argument that can
contains KVM_HEKI_EXIT_REASON_CR0 and KVM_HEKI_EXIT_REASON_CR4. The
returned value is the bitmask of known Heki exit reasons, for now:
KVM_HEKI_EXIT_REASON_CR0 and KVM_HEKI_EXIT_REASON_CR4.
If KVM_CAP_HEKI_CONFIGURE is set, a VM exit will be triggered for each
KVM_HC_LOCK_CR_UPDATE hypercalls according to the requested control
register. This enables to enlighten the VMM with the guest
auto-restrictions.
If KVM_CAP_HEKI_DENIAL is set, a VM exit will be triggered for each
pinned CR violation. This enables the VMM to react to a policy
violation.
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Madhavan T. Venkataraman <madvenka@xxxxxxxxxxxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Cc: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx>
---
Changes since v1:
* New patch. Making user space aware of Heki properties was requested by
Sean Christopherson.
---
arch/x86/kvm/vmx/vmx.c | 5 +-
arch/x86/kvm/x86.c | 114 +++++++++++++++++++++++++++++++++++----
arch/x86/kvm/x86.h | 7 +--
include/linux/kvm_host.h | 2 +
include/uapi/linux/kvm.h | 22 ++++++++
5 files changed, 136 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f487bf16dd96..b631b1d7ba30 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5444,6 +5444,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
int reg;
int err;
int ret;
+ bool exit = false;
exit_qualification = vmx_get_exit_qual(vcpu);
cr = exit_qualification & 15;
@@ -5453,8 +5454,8 @@ static int handle_cr(struct kvm_vcpu *vcpu)
val = kvm_register_read(vcpu, reg);
trace_kvm_cr_write(cr, val);
- ret = heki_check_cr(vcpu, cr, val);
- if (ret)
+ ret = heki_check_cr(vcpu, cr, val, &exit);
+ if (exit)
return ret;
switch (cr) {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4e6c4c21f12c..43c28a6953bf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -119,6 +119,10 @@ static u64 __read_mostly cr4_reserved_bits = CR4_RESERVED_BITS;
#define KVM_CAP_PMU_VALID_MASK KVM_PMU_CAP_DISABLE
+#define KVM_HEKI_EXIT_REASON_VALID_MASK ( \
+ KVM_HEKI_EXIT_REASON_CR0 | \
+ KVM_HEKI_EXIT_REASON_CR4)
+
#define KVM_X2APIC_API_VALID_FLAGS (KVM_X2APIC_API_USE_32BIT_IDS | \
KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK)
@@ -4644,6 +4648,10 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
if (kvm_is_vm_type_supported(KVM_X86_SW_PROTECTED_VM))
r |= BIT(KVM_X86_SW_PROTECTED_VM);
break;
+ case KVM_CAP_HEKI_CONFIGURE:
+ case KVM_CAP_HEKI_DENIAL:
+ r = KVM_HEKI_EXIT_REASON_VALID_MASK;
+ break;
default:
break;
}
@@ -6518,6 +6526,22 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
}
mutex_unlock(&kvm->lock);
break;
+#ifdef CONFIG_HEKI
+ case KVM_CAP_HEKI_CONFIGURE:
+ r = -EINVAL;
+ if (cap->args[0] & ~KVM_HEKI_EXIT_REASON_VALID_MASK)
+ break;
+ kvm->heki_configure_exit_reason = cap->args[0];
+ r = 0;
+ break;
+ case KVM_CAP_HEKI_DENIAL:
+ r = -EINVAL;
+ if (cap->args[0] & ~KVM_HEKI_EXIT_REASON_VALID_MASK)
+ break;
+ kvm->heki_denial_exit_reason = cap->args[0];
+ r = 0;
+ break;
+#endif
default:
r = -EINVAL;
break;
@@ -8056,11 +8080,60 @@ static unsigned long emulator_get_cr(struct x86_emulate_ctxt *ctxt, int cr)
#ifdef CONFIG_HEKI
+static int complete_heki_configure_exit(struct kvm_vcpu *const vcpu)
+{
+ kvm_rax_write(vcpu, 0);
+ ++vcpu->stat.hypercalls;
+ return kvm_skip_emulated_instruction(vcpu);
+}
+
+static int complete_heki_denial_exit(struct kvm_vcpu *const vcpu)
+{
+ kvm_inject_gp(vcpu, 0);
+ return 1;
+}
+
+/* Returns true if the @exit_reason is handled by @vcpu->kvm. */
+static bool heki_exit_cr(struct kvm_vcpu *const vcpu, const __u32 exit_reason,
+ const u64 heki_reason, unsigned long value)
+{
+ switch (exit_reason) {
+ case KVM_EXIT_HEKI_CONFIGURE:
+ if (!(vcpu->kvm->heki_configure_exit_reason & heki_reason))
+ return false;
+
+ vcpu->run->heki_configure.reason = heki_reason;
+ memset(vcpu->run->heki_configure.reserved, 0,
+ sizeof(vcpu->run->heki_configure.reserved));
+ vcpu->run->heki_configure.cr_pinned = value;
+ vcpu->arch.complete_userspace_io = complete_heki_configure_exit;
+ break;
+ case KVM_EXIT_HEKI_DENIAL:
+ if (!(vcpu->kvm->heki_denial_exit_reason & heki_reason))
+ return false;
+
+ vcpu->run->heki_denial.reason = heki_reason;
+ memset(vcpu->run->heki_denial.reserved, 0,
+ sizeof(vcpu->run->heki_denial.reserved));
+ vcpu->run->heki_denial.cr_value = value;
+ vcpu->arch.complete_userspace_io = complete_heki_denial_exit;
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ return false;
+ }
+
+ vcpu->run->exit_reason = exit_reason;
+ return true;
+}
+
#define HEKI_ABI_VERSION 1
static int heki_lock_cr(struct kvm_vcpu *const vcpu, const unsigned long cr,
- unsigned long pin, unsigned long flags)
+ unsigned long pin, unsigned long flags, bool *exit)
{
+ *exit = false;
+
if (flags) {
if ((flags == KVM_LOCK_CR_UPDATE_VERSION) && !cr && !pin)
return HEKI_ABI_VERSION;
@@ -8080,6 +8153,8 @@ static int heki_lock_cr(struct kvm_vcpu *const vcpu, const unsigned long cr,
return -KVM_EINVAL;
atomic_long_or(pin, &vcpu->kvm->heki_pinned_cr0);
+ *exit = heki_exit_cr(vcpu, KVM_EXIT_HEKI_CONFIGURE,
+ KVM_HEKI_EXIT_REASON_CR0, pin);
return 0;
case 4:
/* Checks for irrelevant bits. */
@@ -8089,24 +8164,37 @@ static int heki_lock_cr(struct kvm_vcpu *const vcpu, const unsigned long cr,
/* Ignores bits not present in host. */
pin &= __read_cr4();
atomic_long_or(pin, &vcpu->kvm->heki_pinned_cr4);
+ *exit = heki_exit_cr(vcpu, KVM_EXIT_HEKI_CONFIGURE,
+ KVM_HEKI_EXIT_REASON_CR4, pin);
return 0;
}
return -KVM_EINVAL;
}
+/*
+ * Sets @exit to true if the caller must exit (i.e. denied access) with the
+ * returned value:
+ * - 0 when kvm_run is configured;
+ * - 1 when there is no user space handler.
+ */
int heki_check_cr(struct kvm_vcpu *const vcpu, const unsigned long cr,
- const unsigned long val)
+ const unsigned long val, bool *exit)
{
unsigned long pinned;
+ *exit = false;
+
switch (cr) {
case 0:
pinned = atomic_long_read(&vcpu->kvm->heki_pinned_cr0);
if ((val & pinned) != pinned) {
pr_warn_ratelimited(
"heki: Blocked CR0 update: 0x%lx\n", val);
- kvm_inject_gp(vcpu, 0);
- return 1;
+ *exit = true;
+ if (heki_exit_cr(vcpu, KVM_EXIT_HEKI_DENIAL,
+ KVM_HEKI_EXIT_REASON_CR0, val))
+ return 0;
+ return complete_heki_denial_exit(vcpu);
}
return 0;
case 4:
@@ -8114,8 +8202,11 @@ int heki_check_cr(struct kvm_vcpu *const vcpu, const unsigned long cr,
if ((val & pinned) != pinned) {
pr_warn_ratelimited(
"heki: Blocked CR4 update: 0x%lx\n", val);
- kvm_inject_gp(vcpu, 0);
- return 1;
+ *exit = true;
+ if (heki_exit_cr(vcpu, KVM_EXIT_HEKI_DENIAL,
+ KVM_HEKI_EXIT_REASON_CR4, val))
+ return 0;
+ return complete_heki_denial_exit(vcpu);
}
return 0;
}
@@ -8129,9 +8220,10 @@ static int emulator_set_cr(struct x86_emulate_ctxt *ctxt, int cr, ulong val)
{
struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
int res = 0;
+ bool exit = false;
- res = heki_check_cr(vcpu, cr, val);
- if (res)
+ res = heki_check_cr(vcpu, cr, val, &exit);
+ if (exit)
return res;
switch (cr) {
@@ -9998,7 +10090,11 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
if (a0 > U32_MAX) {
ret = -KVM_EINVAL;
} else {
- ret = heki_lock_cr(vcpu, a0, a1, a2);
+ bool exit = false;
+
+ ret = heki_lock_cr(vcpu, a0, a1, a2, &exit);
+ if (exit)
+ return ret;
}
break;
#endif /* CONFIG_HEKI */
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 193093112b55..f8f5c32bedd9 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -292,18 +292,19 @@ static inline bool kvm_check_has_quirk(struct kvm *kvm, u64 quirk)
#ifdef CONFIG_HEKI
-int heki_check_cr(struct kvm_vcpu *vcpu, unsigned long cr, unsigned long val);
+int heki_check_cr(struct kvm_vcpu *vcpu, unsigned long cr, unsigned long val,
+ bool *exit);
#else /* CONFIG_HEKI */
static inline int heki_check_cr(struct kvm_vcpu *vcpu, unsigned long cr,
- unsigned long val)
+ unsigned long val, bool *exit)
{
return 0;
}
static inline int heki_lock_cr(struct kvm_vcpu *const vcpu, unsigned long cr,
- unsigned long pin)
+ unsigned long pin, bool *exit)
{
return 0;
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6864c80ff936..ec32af17add8 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -838,6 +838,8 @@ struct kvm {
#ifdef CONFIG_HEKI
atomic_long_t heki_pinned_cr0;
atomic_long_t heki_pinned_cr4;
+ u64 heki_configure_exit_reason;
+ u64 heki_denial_exit_reason;
#endif /* CONFIG_HEKI */
#ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 5b5820d19e71..2477b4a16126 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -279,6 +279,8 @@ struct kvm_xen_exit {
#define KVM_EXIT_RISCV_CSR 36
#define KVM_EXIT_NOTIFY 37
#define KVM_EXIT_MEMORY_FAULT 38
+#define KVM_EXIT_HEKI_CONFIGURE 39
+#define KVM_EXIT_HEKI_DENIAL 40
/* For KVM_EXIT_INTERNAL_ERROR */
/* Emulate instruction failed. */
@@ -532,6 +534,24 @@ struct kvm_run {
__u64 gpa;
__u64 size;
} memory_fault;
+ /* KVM_EXIT_HEKI_CONFIGURE */
+ struct {
+#define KVM_HEKI_EXIT_REASON_CR0 (1ULL << 0)
+#define KVM_HEKI_EXIT_REASON_CR4 (1ULL << 1)
+ __u64 reason;
+ union {
+ __u64 cr_pinned;
+ __u64 reserved[7]; /* ignored */
+ };
+ } heki_configure;
+ /* KVM_EXIT_HEKI_DENIAL */
+ struct {
+ __u64 reason;
+ union {
+ __u64 cr_value;
+ __u64 reserved[7]; /* ignored */
+ };
+ } heki_denial;
/* Fix the size of the union. */
char padding[256];
};
@@ -1219,6 +1239,8 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_MEMORY_ATTRIBUTES 232
#define KVM_CAP_GUEST_MEMFD 233
#define KVM_CAP_VM_TYPES 234
+#define KVM_CAP_HEKI_CONFIGURE 235
+#define KVM_CAP_HEKI_DENIAL 236
#ifdef KVM_CAP_IRQ_ROUTING
--
2.42.1