[PATCH 00/16] KVM: x86: Enable APX for guests

[PATCH 00/16] KVM: x86: Enable APX for guests

[Chang S. Bae]

Hi all,

Since the last RFC posting [1], Paolo provided extensive feedback that
helped clarify the overall direction, so this series is now without RFC.
The patchset incorporates those feedbacks throughout, based on v6.19-rc1
where the VEX support series [2] was merged.

Major changes were made on the emulator with rebasing and subsequent
simplifications. Below is a brief summary of each part.

 * Part1, PATCH 01-03: GPR accessor refactoring

   PATCH2: Rename the internal GPR access helpers to kvm_gpr_read_raw() /
   kvm_gpr_write(). These accessors are selectively defined to support
   EGPR indexes. Only with CONFIG_KVM_APX=y, EGPR handling is compiled
   while AMD and 32-bit builds remain unchanged and continue to use the
   existing accessor as is.

 * Part2, PATCH 04-08: VMX support for extended register index

   In the previous version, use of extended VMX fields for EGPR indices
   was conditioned on XCR0.APX. However, enumeration of the APX CPUID bit
   alone is sufficient to guarantee availability of the extended field in
   VMCS. Now, this series checks static_cpu_has(X86_FEATURE_APX) for VMX
   (PATCH8) and the corresponding vCPU value for nested VMX (PATCH7).

 * Part3, PATCH 09-12:  Emulation support for REX2

   This part has the largest changes, with substantial simplification:

   1. PATCH10/11: JMPABS support is dropped, as emulation of memory
      operations are practically meaningful. Then, this drop allows reuse
      of the existing opcode tables with adjustments -- adding the NoRex
      tag for clarifying the #UD behavior with REX2 in PATCH10.
      Subsequently, on PATCH11, REX2-prefixed opcode lookup is then
      integrated into the existing flow by jumping directly to the
      relevant sites.

   2. PATCH11: REX2 disallows several illegal prefix sequences. The
      previous version had pretty complex logic unnecessary. The new
      approach relies on opcode table attributes, which is sufficient and
      makes it simple. This also aligns with the spec sentences [3].

   3. PATCH10: Register index extraction is simplified by a generalized
      helper which interprets REX/REX2 bits.

 * Part4, PATCH13-16: APX exposition and self-test

   There are no changes to CPUID exposure or the self-tests. The only
   adjustment is in XCR0.APX handling to explicitly prevent conflicts
   with MPX (PATCH13). The code that previously referenced XCR0.APX in
   the VMX exit handler was removed with the Part2 changes.

Each patch contains detailed changelogs describing the individual changes.
The previous cover letter [4] also includes some details that were
previously brought up as RFC and now seem to be established.

Thanks to Paolo for the thorough reviews and guidance, and to Chao for
spotting an important point.

The series is also available on this repository:
  git://github.com/intel/apx.git apx-kvm_v1

Thanks,
Chang

[1]: https://lore.kernel.org/kvm/20251110180131.28264-1-chang.seok.bae@intel.com
[2]: https://lore.kernel.org/kvm/20251114003633.60689-1-pbonzini@redhat.com
[3]: https://lore.kernel.org/kvm/20251110180131.28264-1-chang.seok.bae@intel.com
[4]: 3.1.2.1 REX2 Prefix, APX Architecture Specification
     https://cdrdv2.intel.com/v1/dl/getContent/784266

Chang S. Bae (15):
  KVM: x86: Rename register accessors to be GPR-specific
  KVM: x86: Refactor GPR accessors to differentiate register access
    types
  KVM: x86: Implement accessors for extended GPRs
  KVM: VMX: Introduce unified instruction info structure
  KVM: VMX: Refactor instruction information retrieval
  KVM: VMX: Refactor GPR index retrieval from exit qualification
  KVM: nVMX: Propagate the extended instruction info field
  KVM: VMX: Support extended register index in exit handling
  KVM: emulate: Support EGPR accessing and tracking
  KVM: emulate: Handle EGPR index and REX2-incompatible opcodes
  KVM: emulate: Support REX2-prefixed opcode decode
  KVM: emulate: Reject EVEX-prefixed instructions
  KVM: x86: Guard valid XCR0.APX settings
  KVM: x86: Expose APX sub-features to guests
  KVM: x86: selftests: Add APX state handling and XCR0 sanity checks

Peter Fang (1):
  KVM: x86: Expose APX foundational feature bit to guests

 arch/x86/include/asm/kvm_host.h               |  19 +++
 arch/x86/include/asm/kvm_vcpu_regs.h          |  16 +++
 arch/x86/include/asm/vmx.h                    |   2 +
 arch/x86/kvm/Kconfig                          |   4 +
 arch/x86/kvm/cpuid.c                          |  14 +-
 arch/x86/kvm/emulate.c                        | 121 +++++++++++++-----
 arch/x86/kvm/fpu.h                            |  82 ++++++++++++
 arch/x86/kvm/kvm_emulate.h                    |  11 +-
 arch/x86/kvm/reverse_cpuid.h                  |   6 +
 arch/x86/kvm/svm/svm.c                        |  23 +++-
 arch/x86/kvm/vmx/nested.c                     |  87 +++++++------
 arch/x86/kvm/vmx/nested.h                     |   2 +-
 arch/x86/kvm/vmx/vmcs12.c                     |   1 +
 arch/x86/kvm/vmx/vmcs12.h                     |   3 +-
 arch/x86/kvm/vmx/vmx.c                        |  26 ++--
 arch/x86/kvm/vmx/vmx.h                        | 106 +++++++++++++--
 arch/x86/kvm/x86.c                            |  53 ++++++--
 arch/x86/kvm/x86.h                            |  24 +++-
 arch/x86/kvm/xen.c                            |   2 +-
 .../selftests/kvm/include/x86/processor.h     |   1 +
 tools/testing/selftests/kvm/x86/state_test.c  |   6 +
 .../selftests/kvm/x86/xcr0_cpuid_test.c       |  19 +++
 22 files changed, 503 insertions(+), 125 deletions(-)


base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
-- 
2.51.0

[PATCH 01/16] KVM: x86: Rename register accessors to be GPR-specific

[Chang S. Bae]

Refactor the VCPU register state accessors to make them explicitly
GPR-only.

The existing register accessors operate on the cached VCPU register
state. That cache holds GPRs and RIP. RIP has its own interface already.
This renaming clarifies GPR access only.

No functional changes intended.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
No change since last version
---
 arch/x86/kvm/svm/svm.c    |  8 ++++----
 arch/x86/kvm/vmx/nested.c | 20 ++++++++++----------
 arch/x86/kvm/vmx/vmx.c    | 12 ++++++------
 arch/x86/kvm/x86.c        | 10 +++++-----
 arch/x86/kvm/x86.h        |  5 ++---
 arch/x86/kvm/xen.c        |  2 +-
 6 files changed, 28 insertions(+), 29 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index f56c2d895011..ca1dc2342134 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2473,7 +2473,7 @@ static int cr_interception(struct kvm_vcpu *vcpu)
 	err = 0;
 	if (cr >= 16) { /* mov to cr */
 		cr -= 16;
-		val = kvm_register_read(vcpu, reg);
+		val = kvm_gpr_read(vcpu, reg);
 		trace_kvm_cr_write(cr, val);
 		switch (cr) {
 		case 0:
@@ -2519,7 +2519,7 @@ static int cr_interception(struct kvm_vcpu *vcpu)
 			kvm_queue_exception(vcpu, UD_VECTOR);
 			return 1;
 		}
-		kvm_register_write(vcpu, reg, val);
+		kvm_gpr_write(vcpu, reg, val);
 		trace_kvm_cr_read(cr, val);
 	}
 	return kvm_complete_insn_gp(vcpu, err);
@@ -2591,9 +2591,9 @@ static int dr_interception(struct kvm_vcpu *vcpu)
 	dr = svm->vmcb->control.exit_code - SVM_EXIT_READ_DR0;
 	if (dr >= 16) { /* mov to DRn  */
 		dr -= 16;
-		err = kvm_set_dr(vcpu, dr, kvm_register_read(vcpu, reg));
+		err = kvm_set_dr(vcpu, dr, kvm_gpr_read(vcpu, reg));
 	} else {
-		kvm_register_write(vcpu, reg, kvm_get_dr(vcpu, dr));
+		kvm_gpr_write(vcpu, reg, kvm_get_dr(vcpu, dr));
 	}
 
 	return kvm_complete_insn_gp(vcpu, err);
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 40777278eabb..84e2a4a613b7 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5274,9 +5274,9 @@ int get_vmx_mem_address(struct kvm_vcpu *vcpu, unsigned long exit_qualification,
 	else if (addr_size == 0)
 		off = (gva_t)sign_extend64(off, 15);
 	if (base_is_valid)
-		off += kvm_register_read(vcpu, base_reg);
+		off += kvm_gpr_read(vcpu, base_reg);
 	if (index_is_valid)
-		off += kvm_register_read(vcpu, index_reg) << scaling;
+		off += kvm_gpr_read(vcpu, index_reg) << scaling;
 	vmx_get_segment(vcpu, &s, seg_reg);
 
 	/*
@@ -5668,7 +5668,7 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
 		return 1;
 
 	/* Decode instruction info and find the field to read */
-	field = kvm_register_read(vcpu, (((instr_info) >> 28) & 0xf));
+	field = kvm_gpr_read(vcpu, (((instr_info) >> 28) & 0xf));
 
 	if (!nested_vmx_is_evmptr12_valid(vmx)) {
 		/*
@@ -5717,7 +5717,7 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
 	 * on the guest's mode (32 or 64 bit), not on the given field's length.
 	 */
 	if (instr_info & BIT(10)) {
-		kvm_register_write(vcpu, (((instr_info) >> 3) & 0xf), value);
+		kvm_gpr_write(vcpu, (((instr_info) >> 3) & 0xf), value);
 	} else {
 		len = is_64_bit_mode(vcpu) ? 8 : 4;
 		if (get_vmx_mem_address(vcpu, exit_qualification,
@@ -5791,7 +5791,7 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
 		return nested_vmx_failInvalid(vcpu);
 
 	if (instr_info & BIT(10))
-		value = kvm_register_read(vcpu, (((instr_info) >> 3) & 0xf));
+		value = kvm_gpr_read(vcpu, (((instr_info) >> 3) & 0xf));
 	else {
 		len = is_64_bit_mode(vcpu) ? 8 : 4;
 		if (get_vmx_mem_address(vcpu, exit_qualification,
@@ -5802,7 +5802,7 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
 			return kvm_handle_memory_failure(vcpu, r, &e);
 	}
 
-	field = kvm_register_read(vcpu, (((instr_info) >> 28) & 0xf));
+	field = kvm_gpr_read(vcpu, (((instr_info) >> 28) & 0xf));
 
 	offset = get_vmcs12_field_offset(field);
 	if (offset < 0)
@@ -6000,7 +6000,7 @@ static int handle_invept(struct kvm_vcpu *vcpu)
 
 	vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
 	gpr_index = vmx_get_instr_info_reg2(vmx_instruction_info);
-	type = kvm_register_read(vcpu, gpr_index);
+	type = kvm_gpr_read(vcpu, gpr_index);
 
 	types = (vmx->nested.msrs.ept_caps >> VMX_EPT_EXTENT_SHIFT) & 6;
 
@@ -6081,7 +6081,7 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
 
 	vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
 	gpr_index = vmx_get_instr_info_reg2(vmx_instruction_info);
-	type = kvm_register_read(vcpu, gpr_index);
+	type = kvm_gpr_read(vcpu, gpr_index);
 
 	types = (vmx->nested.msrs.vpid_caps &
 			VMX_VPID_EXTENT_SUPPORTED_MASK) >> 8;
@@ -6355,7 +6355,7 @@ static bool nested_vmx_exit_handled_cr(struct kvm_vcpu *vcpu,
 	switch ((exit_qualification >> 4) & 3) {
 	case 0: /* mov to cr */
 		reg = (exit_qualification >> 8) & 15;
-		val = kvm_register_read(vcpu, reg);
+		val = kvm_gpr_read(vcpu, reg);
 		switch (cr) {
 		case 0:
 			if (vmcs12->cr0_guest_host_mask &
@@ -6441,7 +6441,7 @@ static bool nested_vmx_exit_handled_vmcs_access(struct kvm_vcpu *vcpu,
 
 	/* Decode instruction info and find the field to access */
 	vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
-	field = kvm_register_read(vcpu, (((vmx_instruction_info) >> 28) & 0xf));
+	field = kvm_gpr_read(vcpu, (((vmx_instruction_info) >> 28) & 0xf));
 
 	/* Out-of-range fields always cause a VM exit from L2 to L1 */
 	if (field >> 15)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4cbe8c84b636..c944b75c10a7 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5591,7 +5591,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
 	reg = (exit_qualification >> 8) & 15;
 	switch ((exit_qualification >> 4) & 3) {
 	case 0: /* mov to cr */
-		val = kvm_register_read(vcpu, reg);
+		val = kvm_gpr_read(vcpu, reg);
 		trace_kvm_cr_write(cr, val);
 		switch (cr) {
 		case 0:
@@ -5633,12 +5633,12 @@ static int handle_cr(struct kvm_vcpu *vcpu)
 			WARN_ON_ONCE(enable_unrestricted_guest);
 
 			val = kvm_read_cr3(vcpu);
-			kvm_register_write(vcpu, reg, val);
+			kvm_gpr_write(vcpu, reg, val);
 			trace_kvm_cr_read(cr, val);
 			return kvm_skip_emulated_instruction(vcpu);
 		case 8:
 			val = kvm_get_cr8(vcpu);
-			kvm_register_write(vcpu, reg, val);
+			kvm_gpr_write(vcpu, reg, val);
 			trace_kvm_cr_read(cr, val);
 			return kvm_skip_emulated_instruction(vcpu);
 		}
@@ -5708,10 +5708,10 @@ static int handle_dr(struct kvm_vcpu *vcpu)
 
 	reg = DEBUG_REG_ACCESS_REG(exit_qualification);
 	if (exit_qualification & TYPE_MOV_FROM_DR) {
-		kvm_register_write(vcpu, reg, kvm_get_dr(vcpu, dr));
+		kvm_gpr_write(vcpu, reg, kvm_get_dr(vcpu, dr));
 		err = 0;
 	} else {
-		err = kvm_set_dr(vcpu, dr, kvm_register_read(vcpu, reg));
+		err = kvm_set_dr(vcpu, dr, kvm_gpr_read(vcpu, reg));
 	}
 
 out:
@@ -6070,7 +6070,7 @@ static int handle_invpcid(struct kvm_vcpu *vcpu)
 
 	vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
 	gpr_index = vmx_get_instr_info_reg2(vmx_instruction_info);
-	type = kvm_register_read(vcpu, gpr_index);
+	type = kvm_gpr_read(vcpu, gpr_index);
 
 	/* According to the Intel instruction reference, the memory operand
 	 * is read even if it isn't needed (e.g., for type==all)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0c6d899d53dd..23e57170898a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2080,8 +2080,8 @@ static int complete_fast_rdmsr(struct kvm_vcpu *vcpu)
 static int complete_fast_rdmsr_imm(struct kvm_vcpu *vcpu)
 {
 	if (!vcpu->run->msr.error)
-		kvm_register_write(vcpu, vcpu->arch.cui_rdmsr_imm_reg,
-				   vcpu->run->msr.data);
+		kvm_gpr_write(vcpu, vcpu->arch.cui_rdmsr_imm_reg,
+			      vcpu->run->msr.data);
 
 	return complete_fast_msr_access(vcpu);
 }
@@ -2135,7 +2135,7 @@ static int __kvm_emulate_rdmsr(struct kvm_vcpu *vcpu, u32 msr, int reg,
 			kvm_rax_write(vcpu, data & -1u);
 			kvm_rdx_write(vcpu, (data >> 32) & -1u);
 		} else {
-			kvm_register_write(vcpu, reg, data);
+			kvm_gpr_write(vcpu, reg, data);
 		}
 	} else {
 		/* MSR read failed? See if we should ask user space */
@@ -2193,7 +2193,7 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_emulate_wrmsr);
 
 int kvm_emulate_wrmsr_imm(struct kvm_vcpu *vcpu, u32 msr, int reg)
 {
-	return __kvm_emulate_wrmsr(vcpu, msr, kvm_register_read(vcpu, reg));
+	return __kvm_emulate_wrmsr(vcpu, msr, kvm_gpr_read(vcpu, reg));
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_emulate_wrmsr_imm);
 
@@ -2297,7 +2297,7 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(handle_fastpath_wrmsr);
 
 fastpath_t handle_fastpath_wrmsr_imm(struct kvm_vcpu *vcpu, u32 msr, int reg)
 {
-	return __handle_fastpath_wrmsr(vcpu, msr, kvm_register_read(vcpu, reg));
+	return __handle_fastpath_wrmsr(vcpu, msr, kvm_gpr_read(vcpu, reg));
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(handle_fastpath_wrmsr_imm);
 
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index fdab0ad49098..7d6c1c31539f 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -400,15 +400,14 @@ static inline bool vcpu_match_mmio_gpa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	return false;
 }
 
-static inline unsigned long kvm_register_read(struct kvm_vcpu *vcpu, int reg)
+static inline unsigned long kvm_gpr_read(struct kvm_vcpu *vcpu, int reg)
 {
 	unsigned long val = kvm_register_read_raw(vcpu, reg);
 
 	return is_64_bit_mode(vcpu) ? val : (u32)val;
 }
 
-static inline void kvm_register_write(struct kvm_vcpu *vcpu,
-				       int reg, unsigned long val)
+static inline void kvm_gpr_write(struct kvm_vcpu *vcpu, int reg, unsigned long val)
 {
 	if (!is_64_bit_mode(vcpu))
 		val = (u32)val;
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index d6b2a665b499..c9700dc88bb1 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1679,7 +1679,7 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
 	bool handled = false;
 	u8 cpl;
 
-	input = (u64)kvm_register_read(vcpu, VCPU_REGS_RAX);
+	input = (u64)kvm_gpr_read(vcpu, VCPU_REGS_RAX);
 
 	/* Hyper-V hypercalls get bit 31 set in EAX */
 	if ((input & 0x80000000) &&
-- 
2.51.0

[PATCH 02/16] KVM: x86: Refactor GPR accessors to differentiate register access types

[Chang S. Bae]

Refactor the GPR accessors to introduce internal helpers to distinguish
between legacy and extended GPRs. Add CONFIG_KVM_APX to selectively
enable EGPR support.

EGPRs will initially remain unused in the kernel. Thus, the state will
not be saved in KVM register cache on every VM exit. Instead, the guest
state remains live in hardware registers or is stored in guest fpstate.

For now, the EGPR accessors are placeholders to be implemented later.

Link: https://lore.kernel.org/7cff2a78-94f3-4746-9833-c2a1bf51eed6@redhat.com
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
Changes since last version:
* Move kvm_gpr_read_raw() / kvm_gpr_write_raw() into x86.c
  (Paolo: https://lore.kernel.org/33eacd6f-5598-49cb-bb11-ca3a47bfb111@redhat.com)
* Add CONFIG_KVM_APX to compile out R16-R31 handling (Paolo). Massage the
  changelog to note this.
---
 arch/x86/include/asm/kvm_host.h      | 18 ++++++++++++++++
 arch/x86/include/asm/kvm_vcpu_regs.h | 16 ++++++++++++++
 arch/x86/kvm/Kconfig                 |  4 ++++
 arch/x86/kvm/fpu.h                   |  6 ++++++
 arch/x86/kvm/x86.c                   | 32 ++++++++++++++++++++++++++++
 arch/x86/kvm/x86.h                   | 19 +++++++++++++++--
 6 files changed, 93 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5a3bfa293e8b..9dedb8d77222 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -212,6 +212,24 @@ enum {
 	VCPU_SREG_GS,
 	VCPU_SREG_TR,
 	VCPU_SREG_LDTR,
+#ifdef CONFIG_X86_64
+	VCPU_XREG_R16 = __VCPU_XREG_R16,
+	VCPU_XREG_R17 = __VCPU_XREG_R17,
+	VCPU_XREG_R18 = __VCPU_XREG_R18,
+	VCPU_XREG_R19 = __VCPU_XREG_R19,
+	VCPU_XREG_R20 = __VCPU_XREG_R20,
+	VCPU_XREG_R21 = __VCPU_XREG_R21,
+	VCPU_XREG_R22 = __VCPU_XREG_R22,
+	VCPU_XREG_R23 = __VCPU_XREG_R23,
+	VCPU_XREG_R24 = __VCPU_XREG_R24,
+	VCPU_XREG_R25 = __VCPU_XREG_R25,
+	VCPU_XREG_R26 = __VCPU_XREG_R26,
+	VCPU_XREG_R27 = __VCPU_XREG_R27,
+	VCPU_XREG_R28 = __VCPU_XREG_R28,
+	VCPU_XREG_R29 = __VCPU_XREG_R29,
+	VCPU_XREG_R30 = __VCPU_XREG_R30,
+	VCPU_XREG_R31 = __VCPU_XREG_R31,
+#endif
 };
 
 enum exit_fastpath_completion {
diff --git a/arch/x86/include/asm/kvm_vcpu_regs.h b/arch/x86/include/asm/kvm_vcpu_regs.h
index 1af2cb59233b..dd0cc171f405 100644
--- a/arch/x86/include/asm/kvm_vcpu_regs.h
+++ b/arch/x86/include/asm/kvm_vcpu_regs.h
@@ -20,6 +20,22 @@
 #define __VCPU_REGS_R13 13
 #define __VCPU_REGS_R14 14
 #define __VCPU_REGS_R15 15
+#define __VCPU_XREG_R16 16
+#define __VCPU_XREG_R17 17
+#define __VCPU_XREG_R18 18
+#define __VCPU_XREG_R19 19
+#define __VCPU_XREG_R20 20
+#define __VCPU_XREG_R21 21
+#define __VCPU_XREG_R22 22
+#define __VCPU_XREG_R23 23
+#define __VCPU_XREG_R24 24
+#define __VCPU_XREG_R25 25
+#define __VCPU_XREG_R26 26
+#define __VCPU_XREG_R27 27
+#define __VCPU_XREG_R28 28
+#define __VCPU_XREG_R29 29
+#define __VCPU_XREG_R30 30
+#define __VCPU_XREG_R31 31
 #endif
 
 #endif /* _ASM_X86_KVM_VCPU_REGS_H */
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 278f08194ec8..2b2995188e97 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -93,10 +93,14 @@ config KVM_SW_PROTECTED_VM
 
 	  If unsure, say "N".
 
+config KVM_APX
+	bool
+
 config KVM_INTEL
 	tristate "KVM for Intel (and compatible) processors support"
 	depends on KVM && IA32_FEAT_CTL
 	select X86_FRED if X86_64
+	select KVM_APX if X86_64
 	help
 	  Provides support for KVM on processors equipped with Intel's VT
 	  extensions, a.k.a. Virtual Machine Extensions (VMX).
diff --git a/arch/x86/kvm/fpu.h b/arch/x86/kvm/fpu.h
index f898781b6a06..f2613924532d 100644
--- a/arch/x86/kvm/fpu.h
+++ b/arch/x86/kvm/fpu.h
@@ -4,6 +4,7 @@
 #define __KVM_FPU_H_
 
 #include <asm/fpu/api.h>
+#include <asm/kvm_vcpu_regs.h>
 
 typedef u32		__attribute__((vector_size(16))) sse128_t;
 #define __sse128_u	union { sse128_t vec; u64 as_u64[2]; u32 as_u32[4]; }
@@ -203,4 +204,9 @@ static inline void kvm_write_mmx_reg(int reg, const u64 *data)
 	kvm_fpu_put();
 }
 
+#ifdef CONFIG_X86_64
+static inline unsigned long kvm_read_egpr(int reg) { return 0; }
+static inline void kvm_write_egpr(int reg, unsigned long data) { }
+#endif
+
 #endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 23e57170898a..819986edb79c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1255,6 +1255,38 @@ static inline u64 kvm_guest_supported_xfd(struct kvm_vcpu *vcpu)
 }
 #endif
 
+#ifdef CONFIG_KVM_APX
+unsigned long kvm_gpr_read_raw(struct kvm_vcpu *vcpu, int reg)
+{
+	switch (reg) {
+	case VCPU_REGS_RAX ... VCPU_REGS_R15:
+		return kvm_register_read_raw(vcpu, reg);
+	case VCPU_XREG_R16 ... VCPU_XREG_R31:
+		return kvm_read_egpr(reg);
+	default:
+		WARN_ON_ONCE(1);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gpr_read_raw);
+
+void kvm_gpr_write_raw(struct kvm_vcpu *vcpu, int reg, unsigned long val)
+{
+	switch (reg) {
+	case VCPU_REGS_RAX ... VCPU_REGS_R15:
+		kvm_register_write_raw(vcpu, reg, val);
+		break;
+	case VCPU_XREG_R16 ... VCPU_XREG_R31:
+		kvm_write_egpr(reg, val);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+	}
+}
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gpr_write_raw);
+#endif
+
 int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
 {
 	u64 xcr0 = xcr;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 7d6c1c31539f..19183aa92855 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -400,9 +400,24 @@ static inline bool vcpu_match_mmio_gpa(struct kvm_vcpu *vcpu, gpa_t gpa)
 	return false;
 }
 
+#ifdef CONFIG_KVM_APX
+unsigned long kvm_gpr_read_raw(struct kvm_vcpu *vcpu, int reg);
+void kvm_gpr_write_raw(struct kvm_vcpu *vcpu, int reg, unsigned long val);
+#else
+static inline unsigned long kvm_gpr_read_raw(struct kvm_vcpu *vcpu, int reg)
+{
+	return kvm_register_read_raw(vcpu, reg);
+}
+
+static inline void kvm_gpr_write_raw(struct kvm_vcpu *vcpu, int reg, unsigned long val)
+{
+	kvm_register_write_raw(vcpu, reg, val);
+}
+#endif
+
 static inline unsigned long kvm_gpr_read(struct kvm_vcpu *vcpu, int reg)
 {
-	unsigned long val = kvm_register_read_raw(vcpu, reg);
+	unsigned long val = kvm_gpr_read_raw(vcpu, reg);
 
 	return is_64_bit_mode(vcpu) ? val : (u32)val;
 }
@@ -411,7 +426,7 @@ static inline void kvm_gpr_write(struct kvm_vcpu *vcpu, int reg, unsigned long v
 {
 	if (!is_64_bit_mode(vcpu))
 		val = (u32)val;
-	return kvm_register_write_raw(vcpu, reg, val);
+	kvm_gpr_write_raw(vcpu, reg, val);
 }
 
 static inline bool kvm_check_has_quirk(struct kvm *kvm, u64 quirk)
-- 
2.51.0

[PATCH 03/16] KVM: x86: Implement accessors for extended GPRs

[Chang S. Bae]

Add helpers to directly read and write EGPRs (R16–R31).

Unlike legacy GPRs, EGPRs are not cached in vcpu->arch.regs[]. Their
contents remain live in hardware. If preempted, the EGPR state is
preserved in the guest XSAVE buffer.

The Advanced Performance Extensions (APX) feature introduces EGPRs as an
XSAVE-managed state component. The new helpers access the registers
directly between kvm_fpu_get() and kvm_fpu_put().

Callers should ensure that EGPRs are enabled before using these helpers.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
No change since last version
---
 arch/x86/kvm/fpu.h | 80 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 78 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/fpu.h b/arch/x86/kvm/fpu.h
index f2613924532d..f132cad4b49e 100644
--- a/arch/x86/kvm/fpu.h
+++ b/arch/x86/kvm/fpu.h
@@ -148,6 +148,61 @@ static inline void _kvm_write_mmx_reg(int reg, const u64 *data)
 	}
 }
 
+#ifdef CONFIG_X86_64
+/*
+ * Accessors for extended general-purpose registers. binutils >= 2.43 can
+ * recognize those register symbols.
+ */
+
+static inline void _kvm_read_egpr(int reg, unsigned long *data)
+{
+	/* mov %r16..%r31, %rax */
+	switch (reg) {
+	case __VCPU_XREG_R16: asm(".byte 0xd5, 0x48, 0x89, 0xc0" : "=a"(*data)); break;
+	case __VCPU_XREG_R17: asm(".byte 0xd5, 0x48, 0x89, 0xc8" : "=a"(*data)); break;
+	case __VCPU_XREG_R18: asm(".byte 0xd5, 0x48, 0x89, 0xd0" : "=a"(*data)); break;
+	case __VCPU_XREG_R19: asm(".byte 0xd5, 0x48, 0x89, 0xd8" : "=a"(*data)); break;
+	case __VCPU_XREG_R20: asm(".byte 0xd5, 0x48, 0x89, 0xe0" : "=a"(*data)); break;
+	case __VCPU_XREG_R21: asm(".byte 0xd5, 0x48, 0x89, 0xe8" : "=a"(*data)); break;
+	case __VCPU_XREG_R22: asm(".byte 0xd5, 0x48, 0x89, 0xf0" : "=a"(*data)); break;
+	case __VCPU_XREG_R23: asm(".byte 0xd5, 0x48, 0x89, 0xf8" : "=a"(*data)); break;
+	case __VCPU_XREG_R24: asm(".byte 0xd5, 0x4c, 0x89, 0xc0" : "=a"(*data)); break;
+	case __VCPU_XREG_R25: asm(".byte 0xd5, 0x4c, 0x89, 0xc8" : "=a"(*data)); break;
+	case __VCPU_XREG_R26: asm(".byte 0xd5, 0x4c, 0x89, 0xd0" : "=a"(*data)); break;
+	case __VCPU_XREG_R27: asm(".byte 0xd5, 0x4c, 0x89, 0xd8" : "=a"(*data)); break;
+	case __VCPU_XREG_R28: asm(".byte 0xd5, 0x4c, 0x89, 0xe0" : "=a"(*data)); break;
+	case __VCPU_XREG_R29: asm(".byte 0xd5, 0x4c, 0x89, 0xe8" : "=a"(*data)); break;
+	case __VCPU_XREG_R30: asm(".byte 0xd5, 0x4c, 0x89, 0xf0" : "=a"(*data)); break;
+	case __VCPU_XREG_R31: asm(".byte 0xd5, 0x4c, 0x89, 0xf8" : "=a"(*data)); break;
+	default: BUG();
+	}
+}
+
+static inline void _kvm_write_egpr(int reg, unsigned long *data)
+{
+	/* mov %rax, %r16...%r31*/
+	switch (reg) {
+	case __VCPU_XREG_R16: asm(".byte 0xd5, 0x18, 0x89, 0xc0" : : "a"(*data)); break;
+	case __VCPU_XREG_R17: asm(".byte 0xd5, 0x18, 0x89, 0xc1" : : "a"(*data)); break;
+	case __VCPU_XREG_R18: asm(".byte 0xd5, 0x18, 0x89, 0xc2" : : "a"(*data)); break;
+	case __VCPU_XREG_R19: asm(".byte 0xd5, 0x18, 0x89, 0xc3" : : "a"(*data)); break;
+	case __VCPU_XREG_R20: asm(".byte 0xd5, 0x18, 0x89, 0xc4" : : "a"(*data)); break;
+	case __VCPU_XREG_R21: asm(".byte 0xd5, 0x18, 0x89, 0xc5" : : "a"(*data)); break;
+	case __VCPU_XREG_R22: asm(".byte 0xd5, 0x18, 0x89, 0xc6" : : "a"(*data)); break;
+	case __VCPU_XREG_R23: asm(".byte 0xd5, 0x18, 0x89, 0xc7" : : "a"(*data)); break;
+	case __VCPU_XREG_R24: asm(".byte 0xd5, 0x19, 0x89, 0xc0" : : "a"(*data)); break;
+	case __VCPU_XREG_R25: asm(".byte 0xd5, 0x19, 0x89, 0xc1" : : "a"(*data)); break;
+	case __VCPU_XREG_R26: asm(".byte 0xd5, 0x19, 0x89, 0xc2" : : "a"(*data)); break;
+	case __VCPU_XREG_R27: asm(".byte 0xd5, 0x19, 0x89, 0xc3" : : "a"(*data)); break;
+	case __VCPU_XREG_R28: asm(".byte 0xd5, 0x19, 0x89, 0xc4" : : "a"(*data)); break;
+	case __VCPU_XREG_R29: asm(".byte 0xd5, 0x19, 0x89, 0xc5" : : "a"(*data)); break;
+	case __VCPU_XREG_R30: asm(".byte 0xd5, 0x19, 0x89, 0xc6" : : "a"(*data)); break;
+	case __VCPU_XREG_R31: asm(".byte 0xd5, 0x19, 0x89, 0xc7" : : "a"(*data)); break;
+	default: BUG();
+	}
+}
+#endif
+
 static inline void kvm_fpu_get(void)
 {
 	fpregs_lock();
@@ -205,8 +260,29 @@ static inline void kvm_write_mmx_reg(int reg, const u64 *data)
 }
 
 #ifdef CONFIG_X86_64
-static inline unsigned long kvm_read_egpr(int reg) { return 0; }
-static inline void kvm_write_egpr(int reg, unsigned long data) { }
+static inline unsigned long kvm_read_egpr(int reg)
+{
+	unsigned long data;
+
+	if (WARN_ON_ONCE(!cpu_has_xfeatures(XFEATURE_MASK_APX, NULL)))
+		return 0;
+
+	kvm_fpu_get();
+	_kvm_read_egpr(reg, &data);
+	kvm_fpu_put();
+
+	return data;
+}
+
+static inline void kvm_write_egpr(int reg, unsigned long data)
+{
+	if (WARN_ON_ONCE(!cpu_has_xfeatures(XFEATURE_MASK_APX, NULL)))
+		return;
+
+	kvm_fpu_get();
+	_kvm_write_egpr(reg, &data);
+	kvm_fpu_put();
+}
 #endif
 
 #endif
-- 
2.51.0

[PATCH 04/16] KVM: VMX: Introduce unified instruction info structure

[Chang S. Bae]

Define a unified data structure that can represent both the legacy and
extended VMX instruction information formats.

VMX provides per-instruction metadata for VM exits to help decode the
attributes of the instruction that triggered the exit. The legacy format,
however, only supports up to 16 GPRs and thus cannot represent EGPRs. To
support these new registers, VMX introduces an extended 64-bit layout.

Instead of maintaining separate storage for each format, a single
union structure makes the overall handling simple. The field names are
consistent across both layouts. While the presence of certain fields
depends on the instruction type, the offsets remain fixed within each
format.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
No change since last version
---
 arch/x86/kvm/vmx/vmx.h | 61 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index bc3ed3145d7e..567320115a5a 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -311,6 +311,67 @@ struct kvm_vmx {
 	u64 *pid_table;
 };
 
+/*
+ * 32-bit layout of the legacy instruction information field. This format
+ * supports the 16 legacy GPRs.
+ */
+struct base_insn_info {
+	u32 scale		: 2;	/* Scaling factor */
+	u32 reserved1		: 1;
+	u32 reg1		: 4;	/* First register index */
+	u32 asize		: 3;	/* Address size */
+	u32 is_reg		: 1;	/* 0: memory, 1: register */
+	u32 osize		: 2;	/* Operand size */
+	u32 reserved2		: 2;
+	u32 seg			: 3;	/* Segment register index */
+	u32 index		: 4;	/* Index register index */
+	u32 index_invalid	: 1;	/* 0: valid, 1: invalid */
+	u32 base		: 4;	/* Base register index */
+	u32 base_invalid	: 1;	/* 0: valid, 1: invalid */
+	u32 reg2		: 4;	/* Second register index */
+};
+
+/*
+ * 64-bit layout of the extended instruction information field, which
+ * supports EGPRs.
+ */
+struct ext_insn_info {
+	u64 scale		: 2;	/* Scaling factor */
+	u64 asize		: 2;	/* Address size */
+	u64 is_reg		: 1;	/* 0: memory, 1: register */
+	u64 osize		: 2;	/* Operand size */
+	u64 seg			: 3;	/* Segment register index */
+	u64 index_invalid	: 1;	/* 0: valid, 1: invalid */
+	u64 base_invalid	: 1;	/* 0: valid, 1: invalid */
+	u64 reserved1		: 4;
+	u64 reg1		: 5;	/* First register index */
+	u64 reserved2		: 3;
+	u64 index		: 5;	/* Index register index */
+	u64 reserved3		: 3;
+	u64 base		: 5;	/* Base register index */
+	u64 reserved4		: 3;
+	u64 reg2		: 5;	/* Second register index */
+	u64 reserved5		: 19;
+};
+
+/* Union for accessing either the legacy or extended format. */
+union insn_info {
+	struct base_insn_info base;
+	struct ext_insn_info  ext;
+	u32 word;
+	u64 dword;
+};
+
+/*
+ * Wrapper structure combining the instruction info and a flag indicating
+ * whether the extended layout is in use.
+ */
+struct vmx_insn_info {
+	/* true if using the extended layout */
+	bool extended;
+	union insn_info info;
+};
+
 static __always_inline struct vcpu_vt *to_vt(struct kvm_vcpu *vcpu)
 {
 	return &(container_of(vcpu, struct vcpu_vmx, vcpu)->vt);
-- 
2.51.0

[PATCH 05/16] KVM: VMX: Refactor instruction information retrieval

[Chang S. Bae]

Introduce helpers to convert and extract exited instruction attributes,
preparing for EGPR support and deprecating some existing helpers.

Previously, VMX exit handlers directly decoded the raw VMCS field,
resulting in duplicated logic and assumption tied to the legacy layout.

With the unified structure, handlers can convert raw data into a
structure form and access each instruction attribute by field name.

The helper will later determine the format based on the VCPU
configuration. For now, there is no functional change since only the
legacy layout is used.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
No change since last version
---
 arch/x86/kvm/vmx/nested.c | 73 +++++++++++++++++++--------------------
 arch/x86/kvm/vmx/nested.h |  2 +-
 arch/x86/kvm/vmx/vmx.c    | 14 ++++----
 arch/x86/kvm/vmx/vmx.h    | 23 ++++++------
 4 files changed, 57 insertions(+), 55 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 84e2a4a613b7..558f889db621 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5238,7 +5238,7 @@ static void nested_vmx_triple_fault(struct kvm_vcpu *vcpu)
  * #UD, #GP, or #SS.
  */
 int get_vmx_mem_address(struct kvm_vcpu *vcpu, unsigned long exit_qualification,
-			u32 vmx_instruction_info, bool wr, int len, gva_t *ret)
+			struct vmx_insn_info info, bool wr, int len, gva_t *ret)
 {
 	gva_t off;
 	bool exn;
@@ -5252,14 +5252,14 @@ int get_vmx_mem_address(struct kvm_vcpu *vcpu, unsigned long exit_qualification,
 	 * For how an actual address is calculated from all these components,
 	 * refer to Vol. 1, "Operand Addressing".
 	 */
-	int  scaling = vmx_instruction_info & 3;
-	int  addr_size = (vmx_instruction_info >> 7) & 7;
-	bool is_reg = vmx_instruction_info & (1u << 10);
-	int  seg_reg = (vmx_instruction_info >> 15) & 7;
-	int  index_reg = (vmx_instruction_info >> 18) & 0xf;
-	bool index_is_valid = !(vmx_instruction_info & (1u << 22));
-	int  base_reg       = (vmx_instruction_info >> 23) & 0xf;
-	bool base_is_valid  = !(vmx_instruction_info & (1u << 27));
+	int  scaling        = insn_attr(info, scale);
+	int  addr_size      = insn_attr(info, asize);
+	bool is_reg         = insn_attr(info, is_reg);
+	int  seg_reg        = insn_attr(info, seg);
+	int  index_reg      = insn_attr(info, index);
+	bool index_is_valid = !insn_attr(info, index_invalid);
+	int  base_reg       = insn_attr(info, base);
+	bool base_is_valid  = !insn_attr(info, base_invalid);
 
 	if (is_reg) {
 		kvm_queue_exception(vcpu, UD_VECTOR);
@@ -5370,7 +5370,7 @@ static int nested_vmx_get_vmptr(struct kvm_vcpu *vcpu, gpa_t *vmpointer,
 	int r;
 
 	if (get_vmx_mem_address(vcpu, vmx_get_exit_qual(vcpu),
-				vmcs_read32(VMX_INSTRUCTION_INFO), false,
+				vmx_get_insn_info(vcpu), false,
 				sizeof(*vmpointer), &gva)) {
 		*ret = 1;
 		return -EINVAL;
@@ -5655,7 +5655,7 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
 	struct vmcs12 *vmcs12 = is_guest_mode(vcpu) ? get_shadow_vmcs12(vcpu)
 						    : get_vmcs12(vcpu);
 	unsigned long exit_qualification = vmx_get_exit_qual(vcpu);
-	u32 instr_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+	struct vmx_insn_info info = vmx_get_insn_info(vcpu);
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	struct x86_exception e;
 	unsigned long field;
@@ -5668,7 +5668,7 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
 		return 1;
 
 	/* Decode instruction info and find the field to read */
-	field = kvm_gpr_read(vcpu, (((instr_info) >> 28) & 0xf));
+	field = kvm_gpr_read(vcpu, insn_attr(info, reg2));
 
 	if (!nested_vmx_is_evmptr12_valid(vmx)) {
 		/*
@@ -5716,12 +5716,12 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
 	 * Note that the number of bits actually copied is 32 or 64 depending
 	 * on the guest's mode (32 or 64 bit), not on the given field's length.
 	 */
-	if (instr_info & BIT(10)) {
-		kvm_gpr_write(vcpu, (((instr_info) >> 3) & 0xf), value);
+	if (insn_attr(info, is_reg)) {
+		kvm_gpr_write(vcpu, insn_attr(info, reg1), value);
 	} else {
 		len = is_64_bit_mode(vcpu) ? 8 : 4;
 		if (get_vmx_mem_address(vcpu, exit_qualification,
-					instr_info, true, len, &gva))
+					info, true, len, &gva))
 			return 1;
 		/* _system ok, nested_vmx_check_permission has verified cpl=0 */
 		r = kvm_write_guest_virt_system(vcpu, gva, &value, len, &e);
@@ -5761,7 +5761,7 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
 	struct vmcs12 *vmcs12 = is_guest_mode(vcpu) ? get_shadow_vmcs12(vcpu)
 						    : get_vmcs12(vcpu);
 	unsigned long exit_qualification = vmx_get_exit_qual(vcpu);
-	u32 instr_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+	struct vmx_insn_info info = vmx_get_insn_info(vcpu);
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	struct x86_exception e;
 	unsigned long field;
@@ -5790,19 +5790,19 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
 	     get_vmcs12(vcpu)->vmcs_link_pointer == INVALID_GPA))
 		return nested_vmx_failInvalid(vcpu);
 
-	if (instr_info & BIT(10))
-		value = kvm_gpr_read(vcpu, (((instr_info) >> 3) & 0xf));
+	if (insn_attr(info, is_reg))
+		value = kvm_gpr_read(vcpu, insn_attr(info, reg1));
 	else {
 		len = is_64_bit_mode(vcpu) ? 8 : 4;
 		if (get_vmx_mem_address(vcpu, exit_qualification,
-					instr_info, false, len, &gva))
+					info, false, len, &gva))
 			return 1;
 		r = kvm_read_guest_virt(vcpu, gva, &value, len, &e);
 		if (r != X86EMUL_CONTINUE)
 			return kvm_handle_memory_failure(vcpu, r, &e);
 	}
 
-	field = kvm_gpr_read(vcpu, (((instr_info) >> 28) & 0xf));
+	field = kvm_gpr_read(vcpu, insn_attr(info, reg2));
 
 	offset = get_vmcs12_field_offset(field);
 	if (offset < 0)
@@ -5950,7 +5950,7 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu)
 static int handle_vmptrst(struct kvm_vcpu *vcpu)
 {
 	unsigned long exit_qual = vmx_get_exit_qual(vcpu);
-	u32 instr_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+	struct vmx_insn_info info = vmx_get_insn_info(vcpu);
 	gpa_t current_vmptr = to_vmx(vcpu)->nested.current_vmptr;
 	struct x86_exception e;
 	gva_t gva;
@@ -5962,7 +5962,7 @@ static int handle_vmptrst(struct kvm_vcpu *vcpu)
 	if (unlikely(nested_vmx_is_evmptr12_valid(to_vmx(vcpu))))
 		return 1;
 
-	if (get_vmx_mem_address(vcpu, exit_qual, instr_info,
+	if (get_vmx_mem_address(vcpu, exit_qual, info,
 				true, sizeof(gpa_t), &gva))
 		return 1;
 	/* *_system ok, nested_vmx_check_permission has verified cpl=0 */
@@ -5978,15 +5978,16 @@ static int handle_vmptrst(struct kvm_vcpu *vcpu)
 static int handle_invept(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	u32 vmx_instruction_info, types;
 	unsigned long type, roots_to_free;
+	struct vmx_insn_info info;
 	struct kvm_mmu *mmu;
 	gva_t gva;
 	struct x86_exception e;
 	struct {
 		u64 eptp, gpa;
 	} operand;
-	int i, r, gpr_index;
+	u32 types;
+	int i, r;
 
 	if (!(vmx->nested.msrs.secondary_ctls_high &
 	      SECONDARY_EXEC_ENABLE_EPT) ||
@@ -5998,9 +5999,8 @@ static int handle_invept(struct kvm_vcpu *vcpu)
 	if (!nested_vmx_check_permission(vcpu))
 		return 1;
 
-	vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
-	gpr_index = vmx_get_instr_info_reg2(vmx_instruction_info);
-	type = kvm_gpr_read(vcpu, gpr_index);
+	info = vmx_get_insn_info(vcpu);
+	type = kvm_gpr_read(vcpu, insn_attr(info, reg2));
 
 	types = (vmx->nested.msrs.ept_caps >> VMX_EPT_EXTENT_SHIFT) & 6;
 
@@ -6011,7 +6011,7 @@ static int handle_invept(struct kvm_vcpu *vcpu)
 	 * operand is read even if it isn't needed (e.g., for type==global)
 	 */
 	if (get_vmx_mem_address(vcpu, vmx_get_exit_qual(vcpu),
-			vmx_instruction_info, false, sizeof(operand), &gva))
+			info, false, sizeof(operand), &gva))
 		return 1;
 	r = kvm_read_guest_virt(vcpu, gva, &operand, sizeof(operand), &e);
 	if (r != X86EMUL_CONTINUE)
@@ -6058,7 +6058,7 @@ static int handle_invept(struct kvm_vcpu *vcpu)
 static int handle_invvpid(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	u32 vmx_instruction_info;
+	struct vmx_insn_info info;
 	unsigned long type, types;
 	gva_t gva;
 	struct x86_exception e;
@@ -6067,7 +6067,7 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
 		u64 gla;
 	} operand;
 	u16 vpid02;
-	int r, gpr_index;
+	int r;
 
 	if (!(vmx->nested.msrs.secondary_ctls_high &
 	      SECONDARY_EXEC_ENABLE_VPID) ||
@@ -6079,9 +6079,8 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
 	if (!nested_vmx_check_permission(vcpu))
 		return 1;
 
-	vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
-	gpr_index = vmx_get_instr_info_reg2(vmx_instruction_info);
-	type = kvm_gpr_read(vcpu, gpr_index);
+	info = vmx_get_insn_info(vcpu);
+	type = kvm_gpr_read(vcpu, insn_attr(info, reg2));
 
 	types = (vmx->nested.msrs.vpid_caps &
 			VMX_VPID_EXTENT_SUPPORTED_MASK) >> 8;
@@ -6094,7 +6093,7 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
 	 * operand is read even if it isn't needed (e.g., for type==global)
 	 */
 	if (get_vmx_mem_address(vcpu, vmx_get_exit_qual(vcpu),
-			vmx_instruction_info, false, sizeof(operand), &gva))
+			info, false, sizeof(operand), &gva))
 		return 1;
 	r = kvm_read_guest_virt(vcpu, gva, &operand, sizeof(operand), &e);
 	if (r != X86EMUL_CONTINUE)
@@ -6432,7 +6431,7 @@ static bool nested_vmx_exit_handled_encls(struct kvm_vcpu *vcpu,
 static bool nested_vmx_exit_handled_vmcs_access(struct kvm_vcpu *vcpu,
 	struct vmcs12 *vmcs12, gpa_t bitmap)
 {
-	u32 vmx_instruction_info;
+	struct vmx_insn_info info;
 	unsigned long field;
 	u8 b;
 
@@ -6440,8 +6439,8 @@ static bool nested_vmx_exit_handled_vmcs_access(struct kvm_vcpu *vcpu,
 		return true;
 
 	/* Decode instruction info and find the field to access */
-	vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
-	field = kvm_gpr_read(vcpu, (((vmx_instruction_info) >> 28) & 0xf));
+	info = vmx_get_insn_info(vcpu);
+	field = kvm_gpr_read(vcpu, insn_attr(info, reg2));
 
 	/* Out-of-range fields always cause a VM exit from L2 to L1 */
 	if (field >> 15)
diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h
index 983484d42ebf..e54f4e7b3664 100644
--- a/arch/x86/kvm/vmx/nested.h
+++ b/arch/x86/kvm/vmx/nested.h
@@ -50,7 +50,7 @@ void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu);
 int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data);
 int vmx_get_vmx_msr(struct nested_vmx_msrs *msrs, u32 msr_index, u64 *pdata);
 int get_vmx_mem_address(struct kvm_vcpu *vcpu, unsigned long exit_qualification,
-			u32 vmx_instruction_info, bool wr, int len, gva_t *ret);
+			struct vmx_insn_info info, bool wr, int len, gva_t *ret);
 void nested_mark_vmcs12_pages_dirty(struct kvm_vcpu *vcpu);
 bool nested_vmx_check_io_bitmaps(struct kvm_vcpu *vcpu, unsigned int port,
 				 int size);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c944b75c10a7..ae28b06b11f5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6054,29 +6054,27 @@ static int handle_monitor_trap(struct kvm_vcpu *vcpu)
 
 static int handle_invpcid(struct kvm_vcpu *vcpu)
 {
-	u32 vmx_instruction_info;
+	struct vmx_insn_info info;
 	unsigned long type;
 	gva_t gva;
 	struct {
 		u64 pcid;
 		u64 gla;
 	} operand;
-	int gpr_index;
 
 	if (!guest_cpu_cap_has(vcpu, X86_FEATURE_INVPCID)) {
 		kvm_queue_exception(vcpu, UD_VECTOR);
 		return 1;
 	}
 
-	vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
-	gpr_index = vmx_get_instr_info_reg2(vmx_instruction_info);
-	type = kvm_gpr_read(vcpu, gpr_index);
+	info = vmx_get_insn_info(vcpu);
+	type = kvm_gpr_read(vcpu, insn_attr(info, reg2));
 
 	/* According to the Intel instruction reference, the memory operand
 	 * is read even if it isn't needed (e.g., for type==all)
 	 */
 	if (get_vmx_mem_address(vcpu, vmx_get_exit_qual(vcpu),
-				vmx_instruction_info, false,
+				info, false,
 				sizeof(operand), &gva))
 		return 1;
 
@@ -6219,7 +6217,9 @@ static int handle_notify(struct kvm_vcpu *vcpu)
 
 static int vmx_get_msr_imm_reg(struct kvm_vcpu *vcpu)
 {
-	return vmx_get_instr_info_reg(vmcs_read32(VMX_INSTRUCTION_INFO));
+	struct vmx_insn_info info = vmx_get_insn_info(vcpu);
+
+	return insn_attr(info, reg1);
 }
 
 static int handle_rdmsr_imm(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 567320115a5a..ed02a8bcc15e 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -372,6 +372,19 @@ struct vmx_insn_info {
 	union insn_info info;
 };
 
+static inline struct vmx_insn_info vmx_get_insn_info(struct kvm_vcpu *vcpu __maybe_unused)
+{
+	struct vmx_insn_info insn;
+
+	insn.extended  = false;
+	insn.info.word = vmcs_read32(VMX_INSTRUCTION_INFO);
+
+	return insn;
+}
+
+#define insn_attr(insn, attr) \
+	((insn).extended ? (insn).info.ext.attr : (insn).info.base.attr)
+
 static __always_inline struct vcpu_vt *to_vt(struct kvm_vcpu *vcpu)
 {
 	return &(container_of(vcpu, struct vcpu_vmx, vcpu)->vt);
@@ -778,16 +791,6 @@ static inline bool vmx_guest_state_valid(struct kvm_vcpu *vcpu)
 
 void dump_vmcs(struct kvm_vcpu *vcpu);
 
-static inline int vmx_get_instr_info_reg(u32 vmx_instr_info)
-{
-	return (vmx_instr_info >> 3) & 0xf;
-}
-
-static inline int vmx_get_instr_info_reg2(u32 vmx_instr_info)
-{
-	return (vmx_instr_info >> 28) & 0xf;
-}
-
 static inline bool vmx_can_use_ipiv(struct kvm_vcpu *vcpu)
 {
 	return  lapic_in_kernel(vcpu) && enable_ipiv;
-- 
2.51.0

[PATCH 06/16] KVM: VMX: Refactor GPR index retrieval from exit qualification

[Chang S. Bae]

Introduce a helper to extract the GPR index from the exit qualification
field.

VMX exit qualification, in addition to the VMX instruction info field,
encodes a GPR index. With the introduction of EGPRs, this field is
extended by a previously reserved bit position.

This refactoring centralizes the logic so that future updates can handle
the extended GPR index without code duplication.

Since the VMCS exit qualification is cached in VCPU state, it is safe
for the helper to access it directly via the VCPU pointer. This argument
will also be used later to determine EGPR availability.

No functional change intended.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
No change since last version
---
 arch/x86/kvm/vmx/nested.c | 2 +-
 arch/x86/kvm/vmx/vmx.c    | 2 +-
 arch/x86/kvm/vmx/vmx.h    | 5 +++++
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 558f889db621..1e35e1923aec 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6353,7 +6353,7 @@ static bool nested_vmx_exit_handled_cr(struct kvm_vcpu *vcpu,
 
 	switch ((exit_qualification >> 4) & 3) {
 	case 0: /* mov to cr */
-		reg = (exit_qualification >> 8) & 15;
+		reg = vmx_get_exit_qual_gpr(vcpu);
 		val = kvm_gpr_read(vcpu, reg);
 		switch (cr) {
 		case 0:
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index ae28b06b11f5..d41e710e8807 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5588,7 +5588,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
 
 	exit_qualification = vmx_get_exit_qual(vcpu);
 	cr = exit_qualification & 15;
-	reg = (exit_qualification >> 8) & 15;
+	reg = vmx_get_exit_qual_gpr(vcpu);
 	switch ((exit_qualification >> 4) & 3) {
 	case 0: /* mov to cr */
 		val = kvm_gpr_read(vcpu, reg);
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index ed02a8bcc15e..f8dbad161717 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -411,6 +411,11 @@ static __always_inline unsigned long vmx_get_exit_qual(struct kvm_vcpu *vcpu)
 	return vt->exit_qualification;
 }
 
+static inline int vmx_get_exit_qual_gpr(struct kvm_vcpu *vcpu)
+{
+	return (vmx_get_exit_qual(vcpu) >> 8) & 0xf;
+}
+
 static __always_inline u32 vmx_get_intr_info(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vt *vt = to_vt(vcpu);
-- 
2.51.0

[PATCH 07/16] KVM: nVMX: Propagate the extended instruction info field

[Chang S. Bae]

Define the VMCS field offset for the extended instruction information.
Then, propagate the field to nested VMX.

When a virtual CPU enumerates the APX capability, nested VMX should
expose the extended field to address higher register indices.

Link: https://lore.kernel.org/CABgObfa-vqWCenVvvTAoB773AQ+9a1OOT9n5hjqT=zZBDQbb+Q@mail.gmail.com
Suggested-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
Changes since last version:
* Check the availability based on the guest APX capability (Chao)
* Massage the changelog to reflect this fact.
---
 arch/x86/include/asm/vmx.h | 2 ++
 arch/x86/kvm/vmx/nested.c  | 6 ++++++
 arch/x86/kvm/vmx/vmcs12.c  | 1 +
 arch/x86/kvm/vmx/vmcs12.h  | 3 ++-
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index c85c50019523..ab0684948c56 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -264,6 +264,8 @@ enum vmcs_field {
 	PID_POINTER_TABLE_HIGH		= 0x00002043,
 	GUEST_PHYSICAL_ADDRESS          = 0x00002400,
 	GUEST_PHYSICAL_ADDRESS_HIGH     = 0x00002401,
+	EXTENDED_INSTRUCTION_INFO	= 0x00002406,
+	EXTENDED_INSTRUCTION_INFO_HIGH	= 0x00002407,
 	VMCS_LINK_POINTER               = 0x00002800,
 	VMCS_LINK_POINTER_HIGH          = 0x00002801,
 	GUEST_IA32_DEBUGCTL             = 0x00002802,
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 1e35e1923aec..ce972eeaa6f7 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4746,6 +4746,12 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		vmcs12->vm_exit_intr_info = exit_intr_info;
 		vmcs12->vm_exit_instruction_len = exit_insn_len;
 		vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+		/*
+		 * The APX enumeration guarantees the presence of the extended
+		 * fields. This CPUID bit alone is sufficient to rely on it.
+		 */
+		if (guest_cpu_cap_has(vcpu, X86_FEATURE_APX))
+			vmcs12->extended_instruction_info = vmcs_read64(EXTENDED_INSTRUCTION_INFO);
 
 		/*
 		 * According to spec, there's no need to store the guest's
diff --git a/arch/x86/kvm/vmx/vmcs12.c b/arch/x86/kvm/vmx/vmcs12.c
index 4233b5ca9461..ea2b690a419e 100644
--- a/arch/x86/kvm/vmx/vmcs12.c
+++ b/arch/x86/kvm/vmx/vmcs12.c
@@ -53,6 +53,7 @@ const unsigned short vmcs12_field_offsets[] = {
 	FIELD64(XSS_EXIT_BITMAP, xss_exit_bitmap),
 	FIELD64(ENCLS_EXITING_BITMAP, encls_exiting_bitmap),
 	FIELD64(GUEST_PHYSICAL_ADDRESS, guest_physical_address),
+	FIELD64(EXTENDED_INSTRUCTION_INFO, extended_instruction_info),
 	FIELD64(VMCS_LINK_POINTER, vmcs_link_pointer),
 	FIELD64(GUEST_IA32_DEBUGCTL, guest_ia32_debugctl),
 	FIELD64(GUEST_IA32_PAT, guest_ia32_pat),
diff --git a/arch/x86/kvm/vmx/vmcs12.h b/arch/x86/kvm/vmx/vmcs12.h
index 4ad6b16525b9..2146e45aaade 100644
--- a/arch/x86/kvm/vmx/vmcs12.h
+++ b/arch/x86/kvm/vmx/vmcs12.h
@@ -71,7 +71,7 @@ struct __packed vmcs12 {
 	u64 pml_address;
 	u64 encls_exiting_bitmap;
 	u64 tsc_multiplier;
-	u64 padding64[1]; /* room for future expansion */
+	u64 extended_instruction_info;
 	/*
 	 * To allow migration of L1 (complete with its L2 guests) between
 	 * machines of different natural widths (32 or 64 bit), we cannot have
@@ -261,6 +261,7 @@ static inline void vmx_check_vmcs12_offsets(void)
 	CHECK_OFFSET(pml_address, 312);
 	CHECK_OFFSET(encls_exiting_bitmap, 320);
 	CHECK_OFFSET(tsc_multiplier, 328);
+	CHECK_OFFSET(extended_instruction_info, 336);
 	CHECK_OFFSET(cr0_guest_host_mask, 344);
 	CHECK_OFFSET(cr4_guest_host_mask, 352);
 	CHECK_OFFSET(cr0_read_shadow, 360);
-- 
2.51.0

[PATCH 08/16] KVM: VMX: Support extended register index in exit handling

[Chang S. Bae]

Support 5-bit register indices in VMCS fields when APX feature is
enumerated.

The presence of the extended instruction information field is indicated
by APX enumeration, regardless of the XCR0.APX bit setting.

With APX enumerated, the previously reserved bit in the exit qualification
can be referenced safely now. However, there is no guarantee that older
implementations always zeroed this bit.

Link: https://lore.kernel.org/7bb14722-c036-4835-8ed9-046b4e67909e@redhat.com
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
Changes since last version:
* Switch the condition for using the extended instruction information
  from checking XCR0 to relying on APX enumeration (Paolo).
* Rewrite the changelog to clarify this behavior.
---
 arch/x86/kvm/vmx/vmx.h | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index f8dbad161717..937f862f060d 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -372,12 +372,26 @@ struct vmx_insn_info {
 	union insn_info info;
 };
 
-static inline struct vmx_insn_info vmx_get_insn_info(struct kvm_vcpu *vcpu __maybe_unused)
+/*
+ * The APX enumeration guarantees the presence of the extended fields.
+ * The host CPUID bit alone is sufficient to rely on it.
+ */
+static inline bool vmx_insn_info_extended(void)
+{
+	return static_cpu_has(X86_FEATURE_APX);
+}
+
+static inline struct vmx_insn_info vmx_get_insn_info(struct kvm_vcpu *vcpu)
 {
 	struct vmx_insn_info insn;
 
-	insn.extended  = false;
-	insn.info.word = vmcs_read32(VMX_INSTRUCTION_INFO);
+	if (vmx_insn_info_extended()) {
+		insn.extended   = true;
+		insn.info.dword = vmcs_read64(EXTENDED_INSTRUCTION_INFO);
+	} else {
+		insn.extended  = false;
+		insn.info.word = vmcs_read32(VMX_INSTRUCTION_INFO);
+	}
 
 	return insn;
 }
@@ -413,7 +427,10 @@ static __always_inline unsigned long vmx_get_exit_qual(struct kvm_vcpu *vcpu)
 
 static inline int vmx_get_exit_qual_gpr(struct kvm_vcpu *vcpu)
 {
-	return (vmx_get_exit_qual(vcpu) >> 8) & 0xf;
+	if (vmx_insn_info_extended())
+		return (vmx_get_exit_qual(vcpu) >> 8) & 0x1f;
+	else
+		return (vmx_get_exit_qual(vcpu) >> 8) & 0xf;
 }
 
 static __always_inline u32 vmx_get_intr_info(struct kvm_vcpu *vcpu)
-- 
2.51.0

[PATCH 09/16] KVM: emulate: Support EGPR accessing and tracking

[Chang S. Bae]

Extend the emulator context and GPR accessors to handle EGPRs before
adding support for REX2-prefixed instructions.

Now the KVM GPR accessors can handle EGPRs. Then, the emulator can
uniformly cache and track all GPRs without requiring separate handling.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
No change since last version
---
 arch/x86/kvm/kvm_emulate.h | 10 +++++-----
 arch/x86/kvm/x86.c         |  4 ++--
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index fb3dab4b5a53..16b35a796a7f 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -105,13 +105,13 @@ struct x86_instruction_info {
 struct x86_emulate_ops {
 	void (*vm_bugged)(struct x86_emulate_ctxt *ctxt);
 	/*
-	 * read_gpr: read a general purpose register (rax - r15)
+	 * read_gpr: read a general purpose register (rax - r31)
 	 *
 	 * @reg: gpr number.
 	 */
 	ulong (*read_gpr)(struct x86_emulate_ctxt *ctxt, unsigned reg);
 	/*
-	 * write_gpr: write a general purpose register (rax - r15)
+	 * write_gpr: write a general purpose register (rax - r31)
 	 *
 	 * @reg: gpr number.
 	 * @val: value to write.
@@ -314,7 +314,7 @@ typedef void (*fastop_t)(struct fastop *);
  * a ModRM or SIB byte.
  */
 #ifdef CONFIG_X86_64
-#define NR_EMULATOR_GPRS	16
+#define NR_EMULATOR_GPRS	32
 #else
 #define NR_EMULATOR_GPRS	8
 #endif
@@ -373,9 +373,9 @@ struct x86_emulate_ctxt {
 	u8 lock_prefix;
 	u8 rep_prefix;
 	/* bitmaps of registers in _regs[] that can be read */
-	u16 regs_valid;
+	u32 regs_valid;
 	/* bitmaps of registers in _regs[] that have been written */
-	u16 regs_dirty;
+	u32 regs_dirty;
 	/* modrm */
 	u8 modrm;
 	u8 modrm_mod;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 819986edb79c..abbc9b8736e7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8817,12 +8817,12 @@ static bool emulator_guest_cpuid_is_intel_compatible(struct x86_emulate_ctxt *ct
 
 static ulong emulator_read_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg)
 {
-	return kvm_register_read_raw(emul_to_vcpu(ctxt), reg);
+	return kvm_gpr_read_raw(emul_to_vcpu(ctxt), reg);
 }
 
 static void emulator_write_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg, ulong val)
 {
-	kvm_register_write_raw(emul_to_vcpu(ctxt), reg, val);
+	kvm_gpr_write_raw(emul_to_vcpu(ctxt), reg, val);
 }
 
 static void emulator_set_nmi_mask(struct x86_emulate_ctxt *ctxt, bool masked)
-- 
2.51.0

[PATCH 10/16] KVM: emulate: Handle EGPR index and REX2-incompatible opcodes

[Chang S. Bae]

Prepare the emulator for REX2 handling by introducing the NoRex opcode
flag and supporting extended register indices.

Add a helper to factor out common logic for calculating register indices
from a given register identifier and REX bits alone.

REX2 does not support three-byte opcodes. Instead, the REX2.M bit selects
between one- and two-byte opcode tables, which were previously
distinguished by the 0x0F escape byte.

Some legacy instructions in those tables never reference extended
registers. When prefixed with REX, such instructions are treated as if
the prefix were absent. In contrast, a REX2 prefix causes a #UD, which
should be handled explicitly.

Link: https://lore.kernel.org/1ebf3a23-5671-41c1-8daa-c83f2f105936@redhat.com
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
Changes since last version:
* Introduce a dedicated flag to mark REX2-incompatible opcodes (Paolo).
  With JMPABS dropped, there is no longer a need to separate opcode
  tables.
* Refactor register index extraction into a common helper (Paolo) and
  adjust its return value to match existing call sites. Have
  __always_inline to ensure no build issue with
  BUILD_BUG_ON(!__builtin_constant_p(fld))
* Rewrite and clarify the changelog accordingly.
---
 arch/x86/kvm/emulate.c     | 80 +++++++++++++++++++++++---------------
 arch/x86/kvm/kvm_emulate.h |  1 +
 2 files changed, 50 insertions(+), 31 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index c8e292e9a24d..242e043634b9 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -175,6 +175,7 @@
 #define TwoMemOp    ((u64)1 << 55)  /* Instruction has two memory operand */
 #define IsBranch    ((u64)1 << 56)  /* Instruction is considered a branch. */
 #define ShadowStack ((u64)1 << 57)  /* Instruction affects Shadow Stacks. */
+#define NoRex       ((u64)1 << 58)  /* Instruction has no use of REX prefix */
 
 #define DstXacc     (DstAccLo | SrcAccHi | SrcWrite)
 
@@ -244,6 +245,7 @@ enum rex_bits {
 	REX_X = 2,
 	REX_R = 4,
 	REX_W = 8,
+	REX_M = 0x80,
 };
 
 static void writeback_registers(struct x86_emulate_ctxt *ctxt)
@@ -1078,6 +1080,15 @@ static int em_fnstsw(struct x86_emulate_ctxt *ctxt)
 	return X86EMUL_CONTINUE;
 }
 
+static __always_inline int rex_get_rxb(u8 rex, u8 fld)
+{
+	BUILD_BUG_ON(!__builtin_constant_p(fld));
+	BUILD_BUG_ON(fld != REX_B && fld != REX_X && fld != REX_R);
+
+	rex >>= ffs(fld) - 1;
+	return (rex & 1 ? 8 : 0) + (rex & 0x10 ? 16 : 0);
+}
+
 static void __decode_register_operand(struct x86_emulate_ctxt *ctxt,
 				      struct operand *op, int reg)
 {
@@ -1117,7 +1128,7 @@ static void decode_register_operand(struct x86_emulate_ctxt *ctxt,
 	if (ctxt->d & ModRM)
 		reg = ctxt->modrm_reg;
 	else
-		reg = (ctxt->b & 7) | (ctxt->rex_bits & REX_B ? 8 : 0);
+		reg = (ctxt->b & 7) | rex_get_rxb(ctxt->rex_bits, REX_B);
 
 	__decode_register_operand(ctxt, op, reg);
 }
@@ -1136,9 +1147,9 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
 	int rc = X86EMUL_CONTINUE;
 	ulong modrm_ea = 0;
 
-	ctxt->modrm_reg = (ctxt->rex_bits & REX_R ? 8 : 0);
-	index_reg = (ctxt->rex_bits & REX_X ? 8 : 0);
-	base_reg = (ctxt->rex_bits & REX_B ? 8 : 0);
+	ctxt->modrm_reg = rex_get_rxb(ctxt->rex_bits, REX_R);
+	index_reg       = rex_get_rxb(ctxt->rex_bits, REX_X);
+	base_reg        = rex_get_rxb(ctxt->rex_bits, REX_B);
 
 	ctxt->modrm_mod = (ctxt->modrm & 0xc0) >> 6;
 	ctxt->modrm_reg |= (ctxt->modrm & 0x38) >> 3;
@@ -4245,7 +4256,7 @@ static const struct opcode opcode_table[256] = {
 	/* 0x38 - 0x3F */
 	I6ALU(NoWrite, em_cmp), N, N,
 	/* 0x40 - 0x4F */
-	X8(I(DstReg, em_inc)), X8(I(DstReg, em_dec)),
+	X8(I(DstReg | NoRex, em_inc)), X8(I(DstReg | NoRex, em_dec)),
 	/* 0x50 - 0x57 */
 	X8(I(SrcReg | Stack, em_push)),
 	/* 0x58 - 0x5F */
@@ -4263,7 +4274,7 @@ static const struct opcode opcode_table[256] = {
 	I2bvIP(DstDI | SrcDX | Mov | String | Unaligned, em_in, ins, check_perm_in), /* insb, insw/insd */
 	I2bvIP(SrcSI | DstDX | String, em_out, outs, check_perm_out), /* outsb, outsw/outsd */
 	/* 0x70 - 0x7F */
-	X16(D(SrcImmByte | NearBranch | IsBranch)),
+	X16(D(SrcImmByte | NearBranch | IsBranch | NoRex)),
 	/* 0x80 - 0x87 */
 	G(ByteOp | DstMem | SrcImm, group1),
 	G(DstMem | SrcImm, group1),
@@ -4287,15 +4298,15 @@ static const struct opcode opcode_table[256] = {
 	II(ImplicitOps | Stack, em_popf, popf),
 	I(ImplicitOps, em_sahf), I(ImplicitOps, em_lahf),
 	/* 0xA0 - 0xA7 */
-	I2bv(DstAcc | SrcMem | Mov | MemAbs, em_mov),
-	I2bv(DstMem | SrcAcc | Mov | MemAbs | PageTable, em_mov),
-	I2bv(SrcSI | DstDI | Mov | String | TwoMemOp, em_mov),
-	I2bv(SrcSI | DstDI | String | NoWrite | TwoMemOp, em_cmp_r),
+	I2bv(DstAcc | SrcMem | Mov | MemAbs | NoRex, em_mov),
+	I2bv(DstMem | SrcAcc | Mov | MemAbs | PageTable | NoRex, em_mov),
+	I2bv(SrcSI | DstDI | Mov | String | TwoMemOp | NoRex, em_mov),
+	I2bv(SrcSI | DstDI | String | NoWrite | TwoMemOp | NoRex, em_cmp_r),
 	/* 0xA8 - 0xAF */
-	I2bv(DstAcc | SrcImm | NoWrite, em_test),
-	I2bv(SrcAcc | DstDI | Mov | String, em_mov),
-	I2bv(SrcSI | DstAcc | Mov | String, em_mov),
-	I2bv(SrcAcc | DstDI | String | NoWrite, em_cmp_r),
+	I2bv(DstAcc | SrcImm | NoWrite | NoRex, em_test),
+	I2bv(SrcAcc | DstDI | Mov | String | NoRex, em_mov),
+	I2bv(SrcSI | DstAcc | Mov | String | NoRex, em_mov),
+	I2bv(SrcAcc | DstDI | String | NoWrite | NoRex, em_cmp_r),
 	/* 0xB0 - 0xB7 */
 	X8(I(ByteOp | DstReg | SrcImm | Mov, em_mov)),
 	/* 0xB8 - 0xBF */
@@ -4325,17 +4336,17 @@ static const struct opcode opcode_table[256] = {
 	/* 0xD8 - 0xDF */
 	N, E(0, &escape_d9), N, E(0, &escape_db), N, E(0, &escape_dd), N, N,
 	/* 0xE0 - 0xE7 */
-	X3(I(SrcImmByte | NearBranch | IsBranch, em_loop)),
-	I(SrcImmByte | NearBranch | IsBranch, em_jcxz),
-	I2bvIP(SrcImmUByte | DstAcc, em_in,  in,  check_perm_in),
-	I2bvIP(SrcAcc | DstImmUByte, em_out, out, check_perm_out),
+	X3(I(SrcImmByte | NearBranch | IsBranch | NoRex, em_loop)),
+	I(SrcImmByte | NearBranch | IsBranch | NoRex, em_jcxz),
+	I2bvIP(SrcImmUByte | DstAcc | NoRex, em_in,  in,  check_perm_in),
+	I2bvIP(SrcAcc | DstImmUByte | NoRex, em_out, out, check_perm_out),
 	/* 0xE8 - 0xEF */
-	I(SrcImm | NearBranch | IsBranch | ShadowStack, em_call),
-	D(SrcImm | ImplicitOps | NearBranch | IsBranch),
-	I(SrcImmFAddr | No64 | IsBranch, em_jmp_far),
-	D(SrcImmByte | ImplicitOps | NearBranch | IsBranch),
-	I2bvIP(SrcDX | DstAcc, em_in,  in,  check_perm_in),
-	I2bvIP(SrcAcc | DstDX, em_out, out, check_perm_out),
+	I(SrcImm | NearBranch | IsBranch | ShadowStack | NoRex, em_call),
+	D(SrcImm | ImplicitOps | NearBranch | IsBranch | NoRex),
+	I(SrcImmFAddr | No64 | IsBranch | NoRex, em_jmp_far),
+	D(SrcImmByte | ImplicitOps | NearBranch | IsBranch | NoRex),
+	I2bvIP(SrcDX | DstAcc | NoRex, em_in,  in,  check_perm_in),
+	I2bvIP(SrcAcc | DstDX | NoRex, em_out, out, check_perm_out),
 	/* 0xF0 - 0xF7 */
 	N, DI(ImplicitOps, icebp), N, N,
 	DI(ImplicitOps | Priv, hlt), D(ImplicitOps),
@@ -4376,12 +4387,12 @@ static const struct opcode twobyte_table[256] = {
 	N, GP(ModRM | DstMem | SrcReg | Mov | Sse | Avx, &pfx_0f_2b),
 	N, N, N, N,
 	/* 0x30 - 0x3F */
-	II(ImplicitOps | Priv, em_wrmsr, wrmsr),
-	IIP(ImplicitOps, em_rdtsc, rdtsc, check_rdtsc),
-	II(ImplicitOps | Priv, em_rdmsr, rdmsr),
-	IIP(ImplicitOps, em_rdpmc, rdpmc, check_rdpmc),
-	I(ImplicitOps | EmulateOnUD | IsBranch | ShadowStack, em_sysenter),
-	I(ImplicitOps | Priv | EmulateOnUD | IsBranch | ShadowStack, em_sysexit),
+	II(ImplicitOps | Priv | NoRex, em_wrmsr, wrmsr),
+	IIP(ImplicitOps | NoRex, em_rdtsc, rdtsc, check_rdtsc),
+	II(ImplicitOps | Priv | NoRex, em_rdmsr, rdmsr),
+	IIP(ImplicitOps | NoRex, em_rdpmc, rdpmc, check_rdpmc),
+	I(ImplicitOps | EmulateOnUD | IsBranch | ShadowStack | NoRex, em_sysenter),
+	I(ImplicitOps | Priv | EmulateOnUD | IsBranch | ShadowStack | NoRex, em_sysexit),
 	N, N,
 	N, N, N, N, N, N, N, N,
 	/* 0x40 - 0x4F */
@@ -4399,7 +4410,7 @@ static const struct opcode twobyte_table[256] = {
 	N, N, N, N,
 	N, N, N, GP(SrcReg | DstMem | ModRM | Mov, &pfx_0f_6f_0f_7f),
 	/* 0x80 - 0x8F */
-	X16(D(SrcImm | NearBranch | IsBranch)),
+	X16(D(SrcImm | NearBranch | IsBranch | NoRex)),
 	/* 0x90 - 0x9F */
 	X16(D(ByteOp | DstMem | SrcNone | ModRM| Mov)),
 	/* 0xA0 - 0xA7 */
@@ -4992,6 +5003,13 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int
 		opcode = opcode_table[ctxt->b];
 	}
 
+	/*
+	 * Instructions marked with NoRex ignore a legacy REX prefix, but
+	 * #UD should be raised when prefixed with REX2.
+	 */
+	if (ctxt->d & NoRex && ctxt->rex_prefix == REX2_PREFIX)
+		opcode.flags = Undefined;
+
 	if (opcode.flags & ModRM)
 		ctxt->modrm = insn_fetch(u8, ctxt);
 
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 16b35a796a7f..dd5d1e489db6 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -325,6 +325,7 @@ typedef void (*fastop_t)(struct fastop *);
 enum rex_type {
 	REX_NONE,
 	REX_PREFIX,
+	REX2_PREFIX,
 };
 
 struct x86_emulate_ctxt {
-- 
2.51.0

[PATCH 11/16] KVM: emulate: Support REX2-prefixed opcode decode

[Chang S. Bae]

Extend the instruction decoder to recognize and handle the REX2 prefix,
including validation of prefix sequences and correct opcode table
selection.

REX2 is a terminal prefix: once 0xD5 is encountered, the following byte
is the opcode. When REX.M=0, most prefix bytes are invalid after REX2,
including REX, VEX, EVEX, and another REX2. Also, REX2-prefixed
instructions are only valid in 64-bit mode.

All of the invalid prefix combinations after REX2 coincide with opcodes
that are architecturally invalid in 64-bit mode. Thus, marking such
opcodes with No64 in opcode_table[] naturally disallows those illegal
prefix sequences.

The 0x40–0x4F opcode row was missing the No64 flag. While NoRex already
invalidates REX2 for these opcodes, adding No64 makes opcode attributes
explicit and complete.

Link: https://lore.kernel.org/CABgObfYYGTvkYpeyqLSr9JgKMDA_STSff2hXBNchLZuKFU+MMA@mail.gmail.com
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
Changes since last version:
* Simplify REX2 validation logic (Paolo).
* Add direct jumps to the relevant decode paths to reduce control flow
  complexity (Paolo).
* Rewrite and clarify the changelog.
---
 arch/x86/kvm/emulate.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 242e043634b9..fc065ef53400 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4256,7 +4256,7 @@ static const struct opcode opcode_table[256] = {
 	/* 0x38 - 0x3F */
 	I6ALU(NoWrite, em_cmp), N, N,
 	/* 0x40 - 0x4F */
-	X8(I(DstReg | NoRex, em_inc)), X8(I(DstReg | NoRex, em_dec)),
+	X8(I(DstReg | NoRex | No64, em_inc)), X8(I(DstReg | NoRex | No64, em_dec)),
 	/* 0x50 - 0x57 */
 	X8(I(SrcReg | Stack, em_push)),
 	/* 0x58 - 0x5F */
@@ -4850,6 +4850,17 @@ static int x86_decode_avx(struct x86_emulate_ctxt *ctxt,
 	return rc;
 }
 
+static inline bool rex2_invalid(struct x86_emulate_ctxt *ctxt)
+{
+	const struct x86_emulate_ops *ops = ctxt->ops;
+	u64 xcr = 0;
+
+	return ctxt->rex_prefix == REX_PREFIX ||
+	       !(ops->get_cr(ctxt, 4) & X86_CR4_OSXSAVE) ||
+	       ops->get_xcr(ctxt, 0, &xcr) ||
+	       !(xcr & XFEATURE_MASK_APX);
+}
+
 int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int emulation_type)
 {
 	int rc = X86EMUL_CONTINUE;
@@ -4903,7 +4914,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int
 	ctxt->op_bytes = def_op_bytes;
 	ctxt->ad_bytes = def_ad_bytes;
 
-	/* Legacy prefixes. */
+	/* Legacy and REX/REX2 prefixes. */
 	for (;;) {
 		switch (ctxt->b = insn_fetch(u8, ctxt)) {
 		case 0x66:	/* operand-size override */
@@ -4949,6 +4960,17 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int
 			ctxt->rex_prefix = REX_PREFIX;
 			ctxt->rex_bits   = ctxt->b & 0xf;
 			continue;
+		case 0xd5: /* REX2 */
+			if (mode != X86EMUL_MODE_PROT64)
+				goto done_prefixes;
+			if (rex2_invalid(ctxt)) {
+				opcode = ud;
+				goto done_modrm;
+			}
+			ctxt->rex_prefix = REX2_PREFIX;
+			ctxt->rex_bits   = insn_fetch(u8, ctxt);
+			ctxt->b          = insn_fetch(u8, ctxt);
+			goto done_prefixes;
 		case 0xf0:	/* LOCK */
 			ctxt->lock_prefix = 1;
 			break;
@@ -4971,6 +4993,12 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int
 	if (ctxt->rex_bits & REX_W)
 		ctxt->op_bytes = 8;
 
+	/* REX2 opcode is one byte unless M-bit selects the two-byte map */
+	if (ctxt->rex_bits & REX_M)
+		goto decode_twobytes;
+	else if (ctxt->rex_prefix == REX2_PREFIX)
+		goto decode_onebyte;
+
 	/* Opcode byte(s). */
 	if (ctxt->b == 0xc4 || ctxt->b == 0xc5) {
 		/* VEX or LDS/LES */
@@ -4988,17 +5016,19 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int
 			goto done;
 	} else if (ctxt->b == 0x0f) {
 		/* Two- or three-byte opcode */
-		ctxt->opcode_len = 2;
 		ctxt->b = insn_fetch(u8, ctxt);
+decode_twobytes:
+		ctxt->opcode_len = 2;
 		opcode = twobyte_table[ctxt->b];
 
 		/* 0F_38 opcode map */
-		if (ctxt->b == 0x38) {
+		if (ctxt->b == 0x38 && ctxt->rex_prefix != REX2_PREFIX) {
 			ctxt->opcode_len = 3;
 			ctxt->b = insn_fetch(u8, ctxt);
 			opcode = opcode_map_0f_38[ctxt->b];
 		}
 	} else {
+decode_onebyte:
 		/* Opcode byte(s). */
 		opcode = opcode_table[ctxt->b];
 	}
-- 
2.51.0

[PATCH 12/16] KVM: emulate: Reject EVEX-prefixed instructions

[Chang S. Bae]

Explicitly mark EVEX-prefixed opcodes (0x62) as unsupported.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
Changes since last version:
* Rebase onto the recently merged VEX series. Reuse the previously existing
  VEX-rejection logic and style.
---
 arch/x86/kvm/emulate.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index fc065ef53400..820ae381e601 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5040,6 +5040,11 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int
 	if (ctxt->d & NoRex && ctxt->rex_prefix == REX2_PREFIX)
 		opcode.flags = Undefined;
 
+	/* EVEX-prefixed instructions are not implemented */
+	if (ctxt->opcode_len == 1 && ctxt->b == 0x62 &&
+	    (mode == X86EMUL_MODE_PROT64 || (ctxt->modrm & 0xc0) == 0xc0))
+		opcode.flags = NotImpl;
+
 	if (opcode.flags & ModRM)
 		ctxt->modrm = insn_fetch(u8, ctxt);
 
-- 
2.51.0

[PATCH 13/16] KVM: x86: Guard valid XCR0.APX settings

[Chang S. Bae]

Prevent invalid XCR0.APX configurations in two cases: conflict with MPX
and lack of SVM support.

In the non-compacted XSAVE format, APX and MPX conflict on the same
offset. Although MPX is being deprecated in practice, KVM should
explicitly reject such configurations that set both bits.

At this point, only VMX supports EGPRs. SVM will require corresponding
extensions to handle EGPR indices.

The addition to the supported XCR0 mask should accompany guest CPUID
exposure, which will be done separately.

Link: https://lore.kernel.org/ab3f4937-38f5-4354-8850-bf773c159bbe@redhat.com
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
Changes since last version:
* Reject setting MPX and APX bits together in XCR0 (Paolo)
* Remove XCR0 dependency for extended instruction information (Paolo)
* Rewrite the changelog accordingly
---
 arch/x86/kvm/svm/svm.c | 7 ++++++-
 arch/x86/kvm/x86.c     | 4 ++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index ca1dc2342134..85a150e763b2 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5299,8 +5299,13 @@ static __init int svm_hardware_setup(void)
 	}
 	kvm_enable_efer_bits(EFER_NX);
 
+	/*
+	 * APX introduces EGPRs, which require additional VMCB support.
+	 * Disable APX until the necessary extensions are handled.
+	 */
 	kvm_caps.supported_xcr0 &= ~(XFEATURE_MASK_BNDREGS |
-				     XFEATURE_MASK_BNDCSR);
+				     XFEATURE_MASK_BNDCSR  |
+				     XFEATURE_MASK_APX);
 
 	if (boot_cpu_has(X86_FEATURE_FXSR_OPT))
 		kvm_enable_efer_bits(EFER_FFXSR);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index abbc9b8736e7..0c677af83ee4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1314,6 +1314,10 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
 	    (!(xcr0 & XFEATURE_MASK_BNDCSR)))
 		return 1;
 
+	/* MPX and APX conflict in the non-compacted XSAVE format */
+	if (xcr0 & XFEATURE_MASK_BNDREGS && xcr0 & XFEATURE_MASK_APX)
+		return 1;
+
 	if (xcr0 & XFEATURE_MASK_AVX512) {
 		if (!(xcr0 & XFEATURE_MASK_YMM))
 			return 1;
-- 
2.51.0

[PATCH 14/16] KVM: x86: Expose APX foundational feature bit to guests

[Chang S. Bae]

From: Peter Fang <peter.fang@intel.com>

Add the APX xfeature bit to the list of supported XCR0 components and
expose the APX feature to guests. Define the APX CPUID feature bits and
update the maximum supported CPUID leaf to 0x29 to include the APX leaf.
On SVM systems, ensure that the feature is not advertised as EGPR support
is not yet supported.

No APX sub-features are enumerated yet. Those will be exposed in a
separate patch.

Signed-off-by: Peter Fang <peter.fang@intel.com>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
No change since last version
---
 arch/x86/kvm/cpuid.c         | 8 +++++++-
 arch/x86/kvm/reverse_cpuid.h | 2 ++
 arch/x86/kvm/svm/svm.c       | 8 ++++++++
 arch/x86/kvm/x86.c           | 3 ++-
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index d563a948318b..55b32784c392 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1031,6 +1031,7 @@ void kvm_set_cpu_caps(void)
 		F(AVX_VNNI_INT16),
 		F(PREFETCHITI),
 		F(AVX10),
+		SCATTERED_F(APX),
 	);
 
 	kvm_cpu_cap_init(CPUID_7_2_EDX,
@@ -1394,7 +1395,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 	switch (function) {
 	case 0:
 		/* Limited to the highest leaf implemented in KVM. */
-		entry->eax = min(entry->eax, 0x24U);
+		entry->eax = min(entry->eax, 0x29U);
 		break;
 	case 1:
 		cpuid_entry_override(entry, CPUID_1_EDX);
@@ -1639,6 +1640,11 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		entry->edx = 0;
 		break;
 	}
+	case 0x29: {
+		/* No APX sub-features are supported yet */
+		entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+		break;
+	}
 	case KVM_CPUID_SIGNATURE: {
 		const u32 *sigptr = (const u32 *)KVM_SIGNATURE;
 		entry->eax = KVM_CPUID_FEATURES;
diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index 81b4a7acf72e..e538b5444919 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -35,6 +35,7 @@
 #define X86_FEATURE_AVX_VNNI_INT16      KVM_X86_FEATURE(CPUID_7_1_EDX, 10)
 #define X86_FEATURE_PREFETCHITI         KVM_X86_FEATURE(CPUID_7_1_EDX, 14)
 #define X86_FEATURE_AVX10               KVM_X86_FEATURE(CPUID_7_1_EDX, 19)
+#define KVM_X86_FEATURE_APX             KVM_X86_FEATURE(CPUID_7_1_EDX, 21)
 
 /* Intel-defined sub-features, CPUID level 0x00000007:2 (EDX) */
 #define X86_FEATURE_INTEL_PSFD		KVM_X86_FEATURE(CPUID_7_2_EDX, 0)
@@ -125,6 +126,7 @@ static __always_inline u32 __feature_translate(int x86_feature)
 	KVM_X86_TRANSLATE_FEATURE(SGX1);
 	KVM_X86_TRANSLATE_FEATURE(SGX2);
 	KVM_X86_TRANSLATE_FEATURE(SGX_EDECCSSA);
+	KVM_X86_TRANSLATE_FEATURE(APX);
 	KVM_X86_TRANSLATE_FEATURE(CONSTANT_TSC);
 	KVM_X86_TRANSLATE_FEATURE(PERFMON_V2);
 	KVM_X86_TRANSLATE_FEATURE(RRSBA_CTRL);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 85a150e763b2..afc99afa8dea 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5282,6 +5282,14 @@ static __init void svm_set_cpu_caps(void)
 	 */
 	kvm_cpu_cap_clear(X86_FEATURE_BUS_LOCK_DETECT);
 	kvm_cpu_cap_clear(X86_FEATURE_MSR_IMM);
+
+	/*
+	 * If the APX xfeature bit is not supported, meaning that VMCB
+	 * support for EGPRs is unavailable, then the APX feature should
+	 * not be exposed to the guest.
+	 */
+	if (!(kvm_caps.supported_xcr0 & XFEATURE_MASK_APX))
+		kvm_cpu_cap_clear(X86_FEATURE_APX);
 }
 
 static __init int svm_hardware_setup(void)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0c677af83ee4..8b8a532c98eb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -214,7 +214,8 @@ static DEFINE_PER_CPU(struct kvm_user_return_msrs, user_return_msrs);
 #define KVM_SUPPORTED_XCR0     (XFEATURE_MASK_FP | XFEATURE_MASK_SSE \
 				| XFEATURE_MASK_YMM | XFEATURE_MASK_BNDREGS \
 				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
-				| XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)
+				| XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE \
+				| XFEATURE_MASK_APX)
 
 #define XFEATURE_MASK_CET_ALL	(XFEATURE_MASK_CET_USER | XFEATURE_MASK_CET_KERNEL)
 /*
-- 
2.51.0

[PATCH 15/16] KVM: x86: Expose APX sub-features to guests

[Chang S. Bae]

Add CPUID leaf 0x29 sub-leaf 0 to enumerate APX sub-features to guests.
This leaf currently defines the following sub-features:

  * New Conditional Instructions (NCI)
  * New Data Destination (NDD)
  * Flags Suppression (NF)

The CPUID leaf is only exposed if the APX feature is enabled.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
No change since last version
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/cpuid.c            | 10 ++++++++--
 arch/x86/kvm/reverse_cpuid.h    |  4 ++++
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 9dedb8d77222..d75a76152340 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -794,6 +794,7 @@ enum kvm_only_cpuid_leafs {
 	CPUID_24_0_EBX,
 	CPUID_8000_0021_ECX,
 	CPUID_7_1_ECX,
+	CPUID_29_0_EBX,
 	NR_KVM_CPU_CAPS,
 
 	NKVMCAPINTS = NR_KVM_CPU_CAPS - NCAPINTS,
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 55b32784c392..e9437bedcafe 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1063,6 +1063,10 @@ void kvm_set_cpu_caps(void)
 		F(AVX10_512),
 	);
 
+	kvm_cpu_cap_init(CPUID_29_0_EBX,
+		F(APX_NCI_NDD_NF),
+	);
+
 	kvm_cpu_cap_init(CPUID_8000_0001_ECX,
 		F(LAHF_LM),
 		F(CMP_LEGACY),
@@ -1641,8 +1645,10 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		break;
 	}
 	case 0x29: {
-		/* No APX sub-features are supported yet */
-		entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+		if (!(kvm_caps.supported_xcr0 & XFEATURE_MASK_APX)) {
+			entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+			break;
+		}
 		break;
 	}
 	case KVM_CPUID_SIGNATURE: {
diff --git a/arch/x86/kvm/reverse_cpuid.h b/arch/x86/kvm/reverse_cpuid.h
index e538b5444919..f8587586d031 100644
--- a/arch/x86/kvm/reverse_cpuid.h
+++ b/arch/x86/kvm/reverse_cpuid.h
@@ -50,6 +50,9 @@
 #define X86_FEATURE_AVX10_256		KVM_X86_FEATURE(CPUID_24_0_EBX, 17)
 #define X86_FEATURE_AVX10_512		KVM_X86_FEATURE(CPUID_24_0_EBX, 18)
 
+/* Intel-defined sub-features, CPUID level 0x00000029:0 (EBX) */
+#define X86_FEATURE_APX_NCI_NDD_NF	KVM_X86_FEATURE(CPUID_29_0_EBX, 0)
+
 /* CPUID level 0x80000007 (EDX). */
 #define KVM_X86_FEATURE_CONSTANT_TSC	KVM_X86_FEATURE(CPUID_8000_0007_EDX, 8)
 
@@ -91,6 +94,7 @@ static const struct cpuid_reg reverse_cpuid[] = {
 	[CPUID_24_0_EBX]      = {      0x24, 0, CPUID_EBX},
 	[CPUID_8000_0021_ECX] = {0x80000021, 0, CPUID_ECX},
 	[CPUID_7_1_ECX]       = {         7, 1, CPUID_ECX},
+	[CPUID_29_0_EBX]      = {      0x29, 0, CPUID_EBX},
 };
 
 /*
-- 
2.51.0

[PATCH 16/16] KVM: x86: selftests: Add APX state handling and XCR0 sanity checks

[Chang S. Bae]

Now that KVM exposes the APX feature to guests on APX-capable systems,
extend the selftests to validate XCR0 configuration and state management.

Since APX repurposes the XSAVE area previously used by MPX in the
non-compacted format, add a check to ensure that MPX states are not set
when APX is enabled.

Also, load non-init APX state data in the guest so that XSTATE_BV[APX] is
set, allowing validation of APX state testing.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
No change since last version
---
 .../selftests/kvm/include/x86/processor.h     |  1 +
 tools/testing/selftests/kvm/x86/state_test.c  |  6 ++++++
 .../selftests/kvm/x86/xcr0_cpuid_test.c       | 19 +++++++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/x86/processor.h b/tools/testing/selftests/kvm/include/x86/processor.h
index 57d62a425109..6a1da26780ea 100644
--- a/tools/testing/selftests/kvm/include/x86/processor.h
+++ b/tools/testing/selftests/kvm/include/x86/processor.h
@@ -88,6 +88,7 @@ struct xstate {
 #define XFEATURE_MASK_LBR		BIT_ULL(15)
 #define XFEATURE_MASK_XTILE_CFG		BIT_ULL(17)
 #define XFEATURE_MASK_XTILE_DATA	BIT_ULL(18)
+#define XFEATURE_MASK_APX		BIT_ULL(19)
 
 #define XFEATURE_MASK_AVX512		(XFEATURE_MASK_OPMASK | \
 					 XFEATURE_MASK_ZMM_Hi256 | \
diff --git a/tools/testing/selftests/kvm/x86/state_test.c b/tools/testing/selftests/kvm/x86/state_test.c
index f2c7a1c297e3..2b7aa4cca011 100644
--- a/tools/testing/selftests/kvm/x86/state_test.c
+++ b/tools/testing/selftests/kvm/x86/state_test.c
@@ -167,6 +167,12 @@ static void __attribute__((__flatten__)) guest_code(void *arg)
 			asm volatile ("vmovupd %0, %%zmm16" :: "m" (buffer));
 		}
 
+		if (supported_xcr0 & XFEATURE_MASK_APX) {
+			/* mov $0xcccccccc, %r16 */
+			asm volatile (".byte 0xd5, 0x18, 0xb8, 0xcc, 0xcc,"
+				      "0xcc, 0xcc, 0x00, 0x00, 0x00, 0x00");
+		}
+
 		if (this_cpu_has(X86_FEATURE_MPX)) {
 			uint64_t bounds[2] = { 10, 0xffffffffull };
 			uint64_t output[2] = { };
diff --git a/tools/testing/selftests/kvm/x86/xcr0_cpuid_test.c b/tools/testing/selftests/kvm/x86/xcr0_cpuid_test.c
index d038c1571729..e3d3af5ab6f2 100644
--- a/tools/testing/selftests/kvm/x86/xcr0_cpuid_test.c
+++ b/tools/testing/selftests/kvm/x86/xcr0_cpuid_test.c
@@ -46,6 +46,20 @@ do {									\
 		       __supported, (xfeatures));			\
 } while (0)
 
+/*
+ * Verify that mutually exclusive architectural features do not overlap.
+ * For example, APX and MPX must never be reported as supported together.
+ */
+#define ASSERT_XFEATURE_CONFLICT(supported_xcr0, xfeatures, conflicts)			\
+do {											\
+	uint64_t __supported = (supported_xcr0) & ((xfeatures) | (conflicts));		\
+											\
+	__GUEST_ASSERT((__supported & (xfeatures)) != (xfeatures) ||			\
+		       !(__supported & (conflicts)),					\
+		       "supported = 0x%lx, xfeatures = 0x%llx, conflicts = 0x%llx",	\
+		       __supported, (xfeatures), (conflicts));				\
+} while (0)
+
 static void guest_code(void)
 {
 	uint64_t initial_xcr0;
@@ -79,6 +93,11 @@ static void guest_code(void)
 	ASSERT_ALL_OR_NONE_XFEATURE(supported_xcr0,
 				    XFEATURE_MASK_XTILE);
 
+	/* Check APX by ensuring MPX is not exposed concurrently */
+	ASSERT_XFEATURE_CONFLICT(supported_xcr0,
+				 XFEATURE_MASK_APX,
+				 XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR);
+
 	vector = xsetbv_safe(0, XFEATURE_MASK_FP);
 	__GUEST_ASSERT(!vector,
 		       "Expected success on XSETBV(FP), got %s",
-- 
2.51.0

Re: [PATCH 03/16] KVM: x86: Implement accessors for extended GPRs

[Paolo Bonzini]

On 12/21/25 05:07, Chang S. Bae wrote:
> Add helpers to directly read and write EGPRs (R16–R31).
> 
> Unlike legacy GPRs, EGPRs are not cached in vcpu->arch.regs[]. Their
> contents remain live in hardware. If preempted, the EGPR state is
> preserved in the guest XSAVE buffer.
> 
> The Advanced Performance Extensions (APX) feature introduces EGPRs as an
> XSAVE-managed state component. The new helpers access the registers
> directly between kvm_fpu_get() and kvm_fpu_put().
> 
> Callers should ensure that EGPRs are enabled before using these helpers.
> 
> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
> ---
> No change since last version
> ---
>   arch/x86/kvm/fpu.h | 80 ++++++++++++++++++++++++++++++++++++++++++++--
>   1 file changed, 78 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/fpu.h b/arch/x86/kvm/fpu.h
> index f2613924532d..f132cad4b49e 100644
> --- a/arch/x86/kvm/fpu.h
> +++ b/arch/x86/kvm/fpu.h
> @@ -148,6 +148,61 @@ static inline void _kvm_write_mmx_reg(int reg, const u64 *data)
>   	}
>   }
>   
> +#ifdef CONFIG_X86_64
> +/*
> + * Accessors for extended general-purpose registers. binutils >= 2.43 can
> + * recognize those register symbols.
> + */
> +
> +static inline void _kvm_read_egpr(int reg, unsigned long *data)
> +{
> +	/* mov %r16..%r31, %rax */
> +	switch (reg) {
> +	case __VCPU_XREG_R16: asm(".byte 0xd5, 0x48, 0x89, 0xc0" : "=a"(*data)); break;
> +	case __VCPU_XREG_R17: asm(".byte 0xd5, 0x48, 0x89, 0xc8" : "=a"(*data)); break;
> +	case __VCPU_XREG_R18: asm(".byte 0xd5, 0x48, 0x89, 0xd0" : "=a"(*data)); break;
> +	case __VCPU_XREG_R19: asm(".byte 0xd5, 0x48, 0x89, 0xd8" : "=a"(*data)); break;
> +	case __VCPU_XREG_R20: asm(".byte 0xd5, 0x48, 0x89, 0xe0" : "=a"(*data)); break;
> +	case __VCPU_XREG_R21: asm(".byte 0xd5, 0x48, 0x89, 0xe8" : "=a"(*data)); break;
> +	case __VCPU_XREG_R22: asm(".byte 0xd5, 0x48, 0x89, 0xf0" : "=a"(*data)); break;
> +	case __VCPU_XREG_R23: asm(".byte 0xd5, 0x48, 0x89, 0xf8" : "=a"(*data)); break;
> +	case __VCPU_XREG_R24: asm(".byte 0xd5, 0x4c, 0x89, 0xc0" : "=a"(*data)); break;
> +	case __VCPU_XREG_R25: asm(".byte 0xd5, 0x4c, 0x89, 0xc8" : "=a"(*data)); break;
> +	case __VCPU_XREG_R26: asm(".byte 0xd5, 0x4c, 0x89, 0xd0" : "=a"(*data)); break;
> +	case __VCPU_XREG_R27: asm(".byte 0xd5, 0x4c, 0x89, 0xd8" : "=a"(*data)); break;
> +	case __VCPU_XREG_R28: asm(".byte 0xd5, 0x4c, 0x89, 0xe0" : "=a"(*data)); break;
> +	case __VCPU_XREG_R29: asm(".byte 0xd5, 0x4c, 0x89, 0xe8" : "=a"(*data)); break;
> +	case __VCPU_XREG_R30: asm(".byte 0xd5, 0x4c, 0x89, 0xf0" : "=a"(*data)); break;
> +	case __VCPU_XREG_R31: asm(".byte 0xd5, 0x4c, 0x89, 0xf8" : "=a"(*data)); break;
> +	default: BUG();
> +	}
> +}
> +
> +static inline void _kvm_write_egpr(int reg, unsigned long *data)
> +{
> +	/* mov %rax, %r16...%r31*/
> +	switch (reg) {
> +	case __VCPU_XREG_R16: asm(".byte 0xd5, 0x18, 0x89, 0xc0" : : "a"(*data)); break;
> +	case __VCPU_XREG_R17: asm(".byte 0xd5, 0x18, 0x89, 0xc1" : : "a"(*data)); break;
> +	case __VCPU_XREG_R18: asm(".byte 0xd5, 0x18, 0x89, 0xc2" : : "a"(*data)); break;
> +	case __VCPU_XREG_R19: asm(".byte 0xd5, 0x18, 0x89, 0xc3" : : "a"(*data)); break;
> +	case __VCPU_XREG_R20: asm(".byte 0xd5, 0x18, 0x89, 0xc4" : : "a"(*data)); break;
> +	case __VCPU_XREG_R21: asm(".byte 0xd5, 0x18, 0x89, 0xc5" : : "a"(*data)); break;
> +	case __VCPU_XREG_R22: asm(".byte 0xd5, 0x18, 0x89, 0xc6" : : "a"(*data)); break;
> +	case __VCPU_XREG_R23: asm(".byte 0xd5, 0x18, 0x89, 0xc7" : : "a"(*data)); break;
> +	case __VCPU_XREG_R24: asm(".byte 0xd5, 0x19, 0x89, 0xc0" : : "a"(*data)); break;
> +	case __VCPU_XREG_R25: asm(".byte 0xd5, 0x19, 0x89, 0xc1" : : "a"(*data)); break;
> +	case __VCPU_XREG_R26: asm(".byte 0xd5, 0x19, 0x89, 0xc2" : : "a"(*data)); break;
> +	case __VCPU_XREG_R27: asm(".byte 0xd5, 0x19, 0x89, 0xc3" : : "a"(*data)); break;
> +	case __VCPU_XREG_R28: asm(".byte 0xd5, 0x19, 0x89, 0xc4" : : "a"(*data)); break;
> +	case __VCPU_XREG_R29: asm(".byte 0xd5, 0x19, 0x89, 0xc5" : : "a"(*data)); break;
> +	case __VCPU_XREG_R30: asm(".byte 0xd5, 0x19, 0x89, 0xc6" : : "a"(*data)); break;
> +	case __VCPU_XREG_R31: asm(".byte 0xd5, 0x19, 0x89, 0xc7" : : "a"(*data)); break;
> +	default: BUG();
> +	}
> +}
> +#endif

These are also way too big for inlining; move them in x86.c.  Already in 
patch 2,

+#ifdef CONFIG_X86_64
+static inline unsigned long kvm_read_egpr(int reg) { return 0; }
+static inline void kvm_write_egpr(int reg, unsigned long data) { }
+#endif

can be in x86.c.

Paolo

>   static inline void kvm_fpu_get(void)
>   {
>   	fpregs_lock();
> @@ -205,8 +260,29 @@ static inline void kvm_write_mmx_reg(int reg, const u64 *data)
>   }
>   
>   #ifdef CONFIG_X86_64
> -static inline unsigned long kvm_read_egpr(int reg) { return 0; }
> -static inline void kvm_write_egpr(int reg, unsigned long data) { }
> +static inline unsigned long kvm_read_egpr(int reg)
> +{
> +	unsigned long data;
> +
> +	if (WARN_ON_ONCE(!cpu_has_xfeatures(XFEATURE_MASK_APX, NULL)))
> +		return 0;
> +
> +	kvm_fpu_get();
> +	_kvm_read_egpr(reg, &data);
> +	kvm_fpu_put();
> +
> +	return data;
> +}
> +
> +static inline void kvm_write_egpr(int reg, unsigned long data)
> +{
> +	if (WARN_ON_ONCE(!cpu_has_xfeatures(XFEATURE_MASK_APX, NULL)))
> +		return;
> +
> +	kvm_fpu_get();
> +	_kvm_write_egpr(reg, &data);
> +	kvm_fpu_put();
> +}
>   #endif
>   
>   #endif

Re: [PATCH 10/16] KVM: emulate: Handle EGPR index and REX2-incompatible opcodes

[Paolo Bonzini]

On 12/21/25 05:07, Chang S. Bae wrote:
> @@ -175,6 +175,7 @@
>   #define TwoMemOp    ((u64)1 << 55)  /* Instruction has two memory operand */
>   #define IsBranch    ((u64)1 << 56)  /* Instruction is considered a branch. */
>   #define ShadowStack ((u64)1 << 57)  /* Instruction affects Shadow Stacks. */
> +#define NoRex       ((u64)1 << 58)  /* Instruction has no use of REX prefix */

While you have explained in the commit message that these are 
instructions that ignore REX, the flag is only used for REX2 and you're 
defining it based on the REX2 parts of the manual.

So I would call this NoRex2 ("Instruction not present in REX2 maps").

Paolo

Re: [PATCH 00/16] KVM: x86: Enable APX for guests

[Paolo Bonzini]

On 12/21/25 05:07, Chang S. Bae wrote:
> Hi all,
> 
> Since the last RFC posting [1], Paolo provided extensive feedback that
> helped clarify the overall direction, so this series is now without RFC.
> The patchset incorporates those feedbacks throughout, based on v6.19-rc1
> where the VEX support series [2] was merged.
> 
> Major changes were made on the emulator with rebasing and subsequent
> simplifications. Below is a brief summary of each part.

Looks good to me, with just a couple comments that I left on the 
individual patches.

Paolo

Re: [PATCH 08/16] KVM: VMX: Support extended register index in exit handling

[Chao Gao]

On Sun, Dec 21, 2025 at 04:07:34AM +0000, Chang S. Bae wrote:
>Support 5-bit register indices in VMCS fields when APX feature is
>enumerated.
>
>The presence of the extended instruction information field is indicated
>by APX enumeration, regardless of the XCR0.APX bit setting.
>
>With APX enumerated, the previously reserved bit in the exit qualification
>can be referenced safely now. However, there is no guarantee that older
>implementations always zeroed this bit.
>
>Link: https://lore.kernel.org/7bb14722-c036-4835-8ed9-046b4e67909e@redhat.com
>Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
>Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
>---
>Changes since last version:
>* Switch the condition for using the extended instruction information
>  from checking XCR0 to relying on APX enumeration (Paolo).
>* Rewrite the changelog to clarify this behavior.
>---
> arch/x86/kvm/vmx/vmx.h | 25 +++++++++++++++++++++----
> 1 file changed, 21 insertions(+), 4 deletions(-)
>
>diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
>index f8dbad161717..937f862f060d 100644
>--- a/arch/x86/kvm/vmx/vmx.h
>+++ b/arch/x86/kvm/vmx/vmx.h
>@@ -372,12 +372,26 @@ struct vmx_insn_info {
> 	union insn_info info;
> };
> 
>-static inline struct vmx_insn_info vmx_get_insn_info(struct kvm_vcpu *vcpu __maybe_unused)

...

>+/*
>+ * The APX enumeration guarantees the presence of the extended fields.
>+ * The host CPUID bit alone is sufficient to rely on it.
>+ */
>+static inline bool vmx_insn_info_extended(void)
>+{
>+	return static_cpu_has(X86_FEATURE_APX);
>+}
>+
>+static inline struct vmx_insn_info vmx_get_insn_info(struct kvm_vcpu *vcpu)

@vcpu isn't used in the function body, so it should probably be dropped.

> {
> 	struct vmx_insn_info insn;
> 
>-	insn.extended  = false;
>-	insn.info.word = vmcs_read32(VMX_INSTRUCTION_INFO);
>+	if (vmx_insn_info_extended()) {
>+		insn.extended   = true;
>+		insn.info.dword = vmcs_read64(EXTENDED_INSTRUCTION_INFO);
>+	} else {
>+		insn.extended  = false;
>+		insn.info.word = vmcs_read32(VMX_INSTRUCTION_INFO);
>+	}
> 
> 	return insn;
> }

Re: [PATCH 07/16] KVM: nVMX: Propagate the extended instruction info field

[Chao Gao]

On Sun, Dec 21, 2025 at 04:07:33AM +0000, Chang S. Bae wrote:
>Define the VMCS field offset for the extended instruction information.
>Then, propagate the field to nested VMX.
>
>When a virtual CPU enumerates the APX capability, nested VMX should
>expose the extended field to address higher register indices.
>
>Link: https://lore.kernel.org/CABgObfa-vqWCenVvvTAoB773AQ+9a1OOT9n5hjqT=zZBDQbb+Q@mail.gmail.com
>Suggested-by: Chao Gao <chao.gao@intel.com>
>Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
>---
>Changes since last version:
>* Check the availability based on the guest APX capability (Chao)
>* Massage the changelog to reflect this fact.
>---
> arch/x86/include/asm/vmx.h | 2 ++
> arch/x86/kvm/vmx/nested.c  | 6 ++++++
> arch/x86/kvm/vmx/vmcs12.c  | 1 +
> arch/x86/kvm/vmx/vmcs12.h  | 3 ++-
> 4 files changed, 11 insertions(+), 1 deletion(-)
>
>diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
>index c85c50019523..ab0684948c56 100644
>--- a/arch/x86/include/asm/vmx.h
>+++ b/arch/x86/include/asm/vmx.h
>@@ -264,6 +264,8 @@ enum vmcs_field {
> 	PID_POINTER_TABLE_HIGH		= 0x00002043,
> 	GUEST_PHYSICAL_ADDRESS          = 0x00002400,
> 	GUEST_PHYSICAL_ADDRESS_HIGH     = 0x00002401,
>+	EXTENDED_INSTRUCTION_INFO	= 0x00002406,
>+	EXTENDED_INSTRUCTION_INFO_HIGH	= 0x00002407,

Would you mind moving this hunk to patch 8 and swapping patches 7 and 8?

This would separate nested support for EXTENDED_INSTRUCTION_INFO into its own
patch and make it come after the basic (i.e., non-nested) support.

And, an ongoing cleanup [*] may intersect with the new field, so we'll need to
add:
	VMCS12_CASE64(EXTENDED_INSTRUCTION_INFO):
		return vmx_insn_info_extended();

to cpu_has_vmcs12_field() (note: it's a new function added by that cleanup).

[*]: https://lore.kernel.org/kvm/20251230220220.4122282-2-seanjc@google.com/

> 	VMCS_LINK_POINTER               = 0x00002800,
> 	VMCS_LINK_POINTER_HIGH          = 0x00002801,
> 	GUEST_IA32_DEBUGCTL             = 0x00002802,
>diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
>index 1e35e1923aec..ce972eeaa6f7 100644
>--- a/arch/x86/kvm/vmx/nested.c
>+++ b/arch/x86/kvm/vmx/nested.c
>@@ -4746,6 +4746,12 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
> 		vmcs12->vm_exit_intr_info = exit_intr_info;
> 		vmcs12->vm_exit_instruction_len = exit_insn_len;
> 		vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
>+		/*
>+		 * The APX enumeration guarantees the presence of the extended
>+		 * fields. This CPUID bit alone is sufficient to rely on it.
>+		 */
>+		if (guest_cpu_cap_has(vcpu, X86_FEATURE_APX))
>+			vmcs12->extended_instruction_info = vmcs_read64(EXTENDED_INSTRUCTION_INFO);
> 
> 		/*
> 		 * According to spec, there's no need to store the guest's
>diff --git a/arch/x86/kvm/vmx/vmcs12.c b/arch/x86/kvm/vmx/vmcs12.c
>index 4233b5ca9461..ea2b690a419e 100644
>--- a/arch/x86/kvm/vmx/vmcs12.c
>+++ b/arch/x86/kvm/vmx/vmcs12.c
>@@ -53,6 +53,7 @@ const unsigned short vmcs12_field_offsets[] = {
> 	FIELD64(XSS_EXIT_BITMAP, xss_exit_bitmap),
> 	FIELD64(ENCLS_EXITING_BITMAP, encls_exiting_bitmap),
> 	FIELD64(GUEST_PHYSICAL_ADDRESS, guest_physical_address),
>+	FIELD64(EXTENDED_INSTRUCTION_INFO, extended_instruction_info),
> 	FIELD64(VMCS_LINK_POINTER, vmcs_link_pointer),
> 	FIELD64(GUEST_IA32_DEBUGCTL, guest_ia32_debugctl),
> 	FIELD64(GUEST_IA32_PAT, guest_ia32_pat),
>diff --git a/arch/x86/kvm/vmx/vmcs12.h b/arch/x86/kvm/vmx/vmcs12.h
>index 4ad6b16525b9..2146e45aaade 100644
>--- a/arch/x86/kvm/vmx/vmcs12.h
>+++ b/arch/x86/kvm/vmx/vmcs12.h
>@@ -71,7 +71,7 @@ struct __packed vmcs12 {
> 	u64 pml_address;
> 	u64 encls_exiting_bitmap;
> 	u64 tsc_multiplier;
>-	u64 padding64[1]; /* room for future expansion */
>+	u64 extended_instruction_info;
> 	/*
> 	 * To allow migration of L1 (complete with its L2 guests) between
> 	 * machines of different natural widths (32 or 64 bit), we cannot have
>@@ -261,6 +261,7 @@ static inline void vmx_check_vmcs12_offsets(void)
> 	CHECK_OFFSET(pml_address, 312);
> 	CHECK_OFFSET(encls_exiting_bitmap, 320);
> 	CHECK_OFFSET(tsc_multiplier, 328);
>+	CHECK_OFFSET(extended_instruction_info, 336);
> 	CHECK_OFFSET(cr0_guest_host_mask, 344);
> 	CHECK_OFFSET(cr4_guest_host_mask, 352);
> 	CHECK_OFFSET(cr0_read_shadow, 360);
>-- 
>2.51.0
>