[PATCH v5 16/19] KVM:x86: Enable CET virtualization for VMX and advertise to userspace

Yang Weijiang
2023-08-03T07:38:14Z

Enable CET related feature bits in KVM capabilities array and make
X86_CR4_CET available to guest. Remove the feature bits if host side
dependencies cannot be met.

Set the feature bits so that CET features are available in guest CPUID.
Add CR4.CET bit support in order to allow guest set CET master control
bit(CR4.CET).

Disable KVM CET feature if unrestricted_guest is unsupported/disabled as
KVM does not support emulating CET.
Don't expose CET feature if dependent CET bit(U_CET) is cleared in host
XSS or if XSAVES isn't supported.

The CET bits in VM_ENTRY/VM_EXIT control fields should be set to make guest
CET states isolated from host side. CET is only available on platforms that
enumerate VMX_BASIC[bit 56] as 1.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
arch/x86/include/asm/kvm_host.h | 3 ++-
arch/x86/include/asm/msr-index.h | 1 +
arch/x86/kvm/cpuid.c | 12 ++++++++++--
arch/x86/kvm/vmx/capabilities.h | 6 ++++++
arch/x86/kvm/vmx/vmx.c | 20 ++++++++++++++++++++
arch/x86/kvm/vmx/vmx.h | 6 ++++--
arch/x86/kvm/x86.c | 16 +++++++++++++++-
arch/x86/kvm/x86.h | 3 +++
8 files changed, 61 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c50b555234fb..f883696723f4 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -125,7 +125,8 @@
| X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR | X86_CR4_PCIDE \
| X86_CR4_OSXSAVE | X86_CR4_SMEP | X86_CR4_FSGSBASE \
| X86_CR4_OSXMMEXCPT | X86_CR4_LA57 | X86_CR4_VMXE \
- | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP))
+ | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP \
+ | X86_CR4_CET))

#define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 3aedae61af4f..7ce0850c6067 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -1078,6 +1078,7 @@
#define VMX_BASIC_MEM_TYPE_MASK 0x003c000000000000LLU
#define VMX_BASIC_MEM_TYPE_WB 6LLU
#define VMX_BASIC_INOUT 0x0040000000000000LLU
+#define VMX_BASIC_NO_HW_ERROR_CODE 0x0100000000000000LLU

/* Resctrl MSRs: */
/* - Intel: */
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 0338316b827c..1a601be7b4fa 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -624,7 +624,7 @@ void kvm_set_cpu_caps(void)
F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) |
F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) |
F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/ |
- F(SGX_LC) | F(BUS_LOCK_DETECT)
+ F(SGX_LC) | F(BUS_LOCK_DETECT) | F(SHSTK)
);
/* Set LA57 based on hardware capability. */
if (cpuid_ecx(7) & F(LA57))
@@ -642,7 +642,8 @@ void kvm_set_cpu_caps(void)
F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) |
F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM) |
F(SERIALIZE) | F(TSXLDTRK) | F(AVX512_FP16) |
- F(AMX_TILE) | F(AMX_INT8) | F(AMX_BF16) | F(FLUSH_L1D)
+ F(AMX_TILE) | F(AMX_INT8) | F(AMX_BF16) | F(FLUSH_L1D) |
+ F(IBT)
);

/* TSC_ADJUST and ARCH_CAPABILITIES are emulated in software. */
@@ -655,6 +656,13 @@ void kvm_set_cpu_caps(void)
kvm_cpu_cap_set(X86_FEATURE_INTEL_STIBP);
if (boot_cpu_has(X86_FEATURE_AMD_SSBD))
kvm_cpu_cap_set(X86_FEATURE_SPEC_CTRL_SSBD);
+ /*
+ * The feature bit in boot_cpu_data.x86_capability could have been
+ * cleared due to ibt=off cmdline option, then add it back if CPU
+ * supports IBT.
+ */
+ if (cpuid_edx(7) & F(IBT))
+ kvm_cpu_cap_set(X86_FEATURE_IBT);

kvm_cpu_cap_mask(CPUID_7_1_EAX,
F(AVX_VNNI) | F(AVX512_BF16) | F(CMPCCXADD) |
diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index b1883f6c08eb..2948a288d0b4 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -79,6 +79,12 @@ static inline bool cpu_has_vmx_basic_inout(void)
return (((u64)vmcs_config.basic_cap << 32) & VMX_BASIC_INOUT);
}

+static inline bool cpu_has_vmx_basic_no_hw_errcode(void)
+{
+ return ((u64)vmcs_config.basic_cap << 32) &
+ VMX_BASIC_NO_HW_ERROR_CODE;
+}
+
static inline bool cpu_has_virtual_nmis(void)
{
return vmcs_config.pin_based_exec_ctrl & PIN_BASED_VIRTUAL_NMIS &&
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 96e22515ed13..2f2b6f7c33d9 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2624,6 +2624,7 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
{ VM_ENTRY_LOAD_IA32_EFER, VM_EXIT_LOAD_IA32_EFER },
{ VM_ENTRY_LOAD_BNDCFGS, VM_EXIT_CLEAR_BNDCFGS },
{ VM_ENTRY_LOAD_IA32_RTIT_CTL, VM_EXIT_CLEAR_IA32_RTIT_CTL },
+ { VM_ENTRY_LOAD_CET_STATE, VM_EXIT_LOAD_CET_STATE },
};

memset(vmcs_conf, 0, sizeof(*vmcs_conf));
@@ -6357,6 +6358,12 @@ void dump_vmcs(struct kvm_vcpu *vcpu)
if (vmcs_read32(VM_EXIT_MSR_STORE_COUNT) > 0)
vmx_dump_msrs("guest autostore", &vmx->msr_autostore.guest);

+ if (vmentry_ctl & VM_ENTRY_LOAD_CET_STATE) {
+ pr_err("S_CET = 0x%016lx\n", vmcs_readl(GUEST_S_CET));
+ pr_err("SSP = 0x%016lx\n", vmcs_readl(GUEST_SSP));
+ pr_err("INTR SSP TABLE = 0x%016lx\n",
+ vmcs_readl(GUEST_INTR_SSP_TABLE));
+ }
pr_err("*** Host State ***\n");
pr_err("RIP = 0x%016lx RSP = 0x%016lx\n",
vmcs_readl(HOST_RIP), vmcs_readl(HOST_RSP));
@@ -6434,6 +6441,12 @@ void dump_vmcs(struct kvm_vcpu *vcpu)
if (secondary_exec_control & SECONDARY_EXEC_ENABLE_VPID)
pr_err("Virtual processor ID = 0x%04x\n",
vmcs_read16(VIRTUAL_PROCESSOR_ID));
+ if (vmexit_ctl & VM_EXIT_LOAD_CET_STATE) {
+ pr_err("S_CET = 0x%016lx\n", vmcs_readl(HOST_S_CET));
+ pr_err("SSP = 0x%016lx\n", vmcs_readl(HOST_SSP));
+ pr_err("INTR SSP TABLE = 0x%016lx\n",
+ vmcs_readl(HOST_INTR_SSP_TABLE));
+ }
}

/*
@@ -7970,6 +7983,13 @@ static __init void vmx_set_cpu_caps(void)

if (cpu_has_vmx_waitpkg())
kvm_cpu_cap_check_and_set(X86_FEATURE_WAITPKG);
+
+ if (!cpu_has_load_cet_ctrl() || !enable_unrestricted_guest ||
+ !cpu_has_vmx_basic_no_hw_errcode()) {
+ kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
+ kvm_cpu_cap_clear(X86_FEATURE_IBT);
+ kvm_caps.supported_xss &= ~CET_XSTATE_MASK;
+ }
}

static void vmx_request_immediate_exit(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 32384ba38499..4e88b5fb45e8 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -481,7 +481,8 @@ static inline u8 vmx_get_rvi(void)
VM_ENTRY_LOAD_IA32_EFER | \
VM_ENTRY_LOAD_BNDCFGS | \
VM_ENTRY_PT_CONCEAL_PIP | \
- VM_ENTRY_LOAD_IA32_RTIT_CTL)
+ VM_ENTRY_LOAD_IA32_RTIT_CTL | \
+ VM_ENTRY_LOAD_CET_STATE)

#define __KVM_REQUIRED_VMX_VM_EXIT_CONTROLS \
(VM_EXIT_SAVE_DEBUG_CONTROLS | \
@@ -503,7 +504,8 @@ static inline u8 vmx_get_rvi(void)
VM_EXIT_LOAD_IA32_EFER | \
VM_EXIT_CLEAR_BNDCFGS | \
VM_EXIT_PT_CONCEAL_PIP | \
- VM_EXIT_CLEAR_IA32_RTIT_CTL)
+ VM_EXIT_CLEAR_IA32_RTIT_CTL | \
+ VM_EXIT_LOAD_CET_STATE)

#define KVM_REQUIRED_VMX_PIN_BASED_VM_EXEC_CONTROL \
(PIN_BASED_EXT_INTR_MASK | \
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fa3e7f7c639f..aa92dec66f1e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -230,7 +230,7 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
| XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)

-#define KVM_SUPPORTED_XSS 0
+#define KVM_SUPPORTED_XSS (XFEATURE_MASK_CET_USER)

u64 __read_mostly host_efer;
EXPORT_SYMBOL_GPL(host_efer);
@@ -9669,6 +9669,20 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)

kvm_ops_update(ops);

+ if (!kvm_is_cet_supported()) {
+ kvm_cpu_cap_clear(X86_FEATURE_SHSTK);
+ kvm_cpu_cap_clear(X86_FEATURE_IBT);
+ }
+
+ /*
+ * If SHSTK and IBT are not available in KVM, clear CET user bit in
+ * kvm_caps.supported_xss so that kvm_is_cet__supported() returns
+ * false when called.
+ */
+ if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK) &&
+ !kvm_cpu_cap_has(X86_FEATURE_IBT))
+ kvm_caps.supported_xss &= ~CET_XSTATE_MASK;
+
for_each_online_cpu(cpu) {
smp_call_function_single(cpu, kvm_x86_check_cpu_compat, &r, 1);
if (r < 0)
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index e42e5263fcf7..373386fb9ed2 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -542,6 +542,9 @@ bool kvm_msr_allowed(struct kvm_vcpu *vcpu, u32 index, u32 type);
__reserved_bits |= X86_CR4_VMXE; \
if (!__cpu_has(__c, X86_FEATURE_PCID)) \
__reserved_bits |= X86_CR4_PCIDE; \
+ if (!__cpu_has(__c, X86_FEATURE_SHSTK) && \
+ !__cpu_has(__c, X86_FEATURE_IBT)) \
+ __reserved_bits |= X86_CR4_CET; \
__reserved_bits; \
})

--
2.27.0