[PATCH v11 14/16] KVM: emulator: Add emulation of LASS violation checks on linear address

[Binbin Wu]

From: Zeng Guang <guang.zeng@xxxxxxxxx>

When Intel Linear Address Space Separation (LASS) is enabled, the
processor applies a LASS violation check to every access to a linear
address. To align with hardware behavior, KVM needs to perform the
same check in instruction emulation.

Define a new function in x86_emulator_ops to perform the LASS violation
check in KVM emulator. The function accepts an address and a size, which
delimit the memory access, and a flag, which provides extra information
about the access that is necessary for LASS violation checks, e.g., whether
the access is an instruction fetch or implicit access.

emulator_is_lass_violation() is just a placeholder. it will be wired up
to VMX/SVM implementation by a later patch.

Signed-off-by: Zeng Guang <guang.zeng@xxxxxxxxx>
Signed-off-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>
Tested-by: Xuelian Guo <xuelian.guo@xxxxxxxxx>
---
 arch/x86/include/asm/kvm-x86-ops.h |  3 ++-
 arch/x86/include/asm/kvm_host.h    |  3 +++
 arch/x86/kvm/emulate.c             | 11 +++++++++++
 arch/x86/kvm/kvm_emulate.h         |  3 +++
 arch/x86/kvm/x86.c                 | 10 ++++++++++
 5 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 179931b73876..fc9945e80177 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -133,8 +133,9 @@ KVM_X86_OP_OPTIONAL(migrate_timers)
 KVM_X86_OP(msr_filter_changed)
 KVM_X86_OP(complete_emulated_msr)
 KVM_X86_OP(vcpu_deliver_sipi_vector)
-KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons);
+KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons)
 KVM_X86_OP(get_untagged_addr)
+KVM_X86_OP_OPTIONAL_RET0(is_lass_violation)
 
 #undef KVM_X86_OP
 #undef KVM_X86_OP_OPTIONAL
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d4e3657b840a..3e73fc45c8e6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1754,6 +1754,9 @@ struct kvm_x86_ops {
 	unsigned long (*vcpu_get_apicv_inhibit_reasons)(struct kvm_vcpu *vcpu);
 
 	gva_t (*get_untagged_addr)(struct kvm_vcpu *vcpu, gva_t gva, unsigned int flags);
+
+	bool (*is_lass_violation)(struct kvm_vcpu *vcpu, unsigned long addr,
+				  unsigned int size, unsigned int flags);
 };
 
 struct kvm_x86_nested_ops {
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 7af58b8d57ac..cbd08daeae9e 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -742,6 +742,10 @@ static __always_inline int __linearize(struct x86_emulate_ctxt *ctxt,
 		}
 		break;
 	}
+
+	if (ctxt->ops->is_lass_violation(ctxt, *linear, size, flags))
+		goto bad;
+
 	if (la & (insn_alignment(ctxt, size) - 1))
 		return emulate_gp(ctxt, 0);
 	return X86EMUL_CONTINUE;
@@ -848,6 +852,9 @@ static inline int jmp_rel(struct x86_emulate_ctxt *ctxt, int rel)
 static int linear_read_system(struct x86_emulate_ctxt *ctxt, ulong linear,
 			      void *data, unsigned size)
 {
+	if (ctxt->ops->is_lass_violation(ctxt, linear, size, X86EMUL_F_IMPLICIT))
+		return emulate_gp(ctxt, 0);
+
 	return ctxt->ops->read_std(ctxt, linear, data, size, &ctxt->exception, true);
 }
 
@@ -855,6 +862,10 @@ static int linear_write_system(struct x86_emulate_ctxt *ctxt,
 			       ulong linear, void *data,
 			       unsigned int size)
 {
+	if (ctxt->ops->is_lass_violation(ctxt, linear, size,
+					 X86EMUL_F_IMPLICIT | X86EMUL_F_WRITE))
+		return emulate_gp(ctxt, 0);
+
 	return ctxt->ops->write_std(ctxt, linear, data, size, &ctxt->exception, true);
 }
 
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 26f402616604..a76baa51fa16 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -234,6 +234,9 @@ struct x86_emulate_ops {
 
 	gva_t (*get_untagged_addr)(struct x86_emulate_ctxt *ctxt, gva_t addr,
 				   unsigned int flags);
+
+	bool (*is_lass_violation)(struct x86_emulate_ctxt *ctxt, unsigned long addr,
+				  unsigned int size, unsigned int flags);
 };
 
 /* Type, address-of, and value of an instruction's operand. */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4c2cdfcae79d..58d7a9241630 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8317,6 +8317,15 @@ static gva_t emulator_get_untagged_addr(struct x86_emulate_ctxt *ctxt,
 	return static_call(kvm_x86_get_untagged_addr)(emul_to_vcpu(ctxt), addr, flags);
 }
 
+static bool emulator_is_lass_violation(struct x86_emulate_ctxt *ctxt,
+				       unsigned long addr,
+				       unsigned int size,
+				       unsigned int flags)
+{
+	return static_call(kvm_x86_is_lass_violation)(emul_to_vcpu(ctxt),
+						      addr, size, flags);
+}
+
 static const struct x86_emulate_ops emulate_ops = {
 	.vm_bugged           = emulator_vm_bugged,
 	.read_gpr            = emulator_read_gpr,
@@ -8362,6 +8371,7 @@ static const struct x86_emulate_ops emulate_ops = {
 	.triple_fault        = emulator_triple_fault,
 	.set_xcr             = emulator_set_xcr,
 	.get_untagged_addr   = emulator_get_untagged_addr,
+	.is_lass_violation   = emulator_is_lass_violation,
 };
 
 static void toggle_interruptibility(struct kvm_vcpu *vcpu, u32 mask)
-- 
2.25.1