[PATCH RFC 05/10] KVM: VMX: Introduce SPP-Induced vm exit and it's handle.

[Zhang Yi]

From: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>

Accesses using guest-physical addresses may cause SPP-induced VM exits
due to an SPPT misconfiguration or an
SPPT miss. The basic VM exit reason code reported for SPP-induced VM
exits is 66.

An SPPT misconfiguration VM exit occurs when, in the course of
translating a guest-physical address, the logical processor encounters
a leaf EPT paging-structure entry mapping a 4KB page for which the
sub-page write permission control bit is set and during the SPPT lookup
an SPPT paging-structure entry contains an unsupported value.

An SPPT miss VM exit occurs when, in the course of translation a
guest-physical address, the logical processor encounters a leaf
EPT paging-structure entry for which the sub-page write permission
control bit is set and during the SPPT lookup there is no SPPT
misconfiguration but any level of SPPT paging-structure entries
are not-present.

SPPT misconfigurations and SPPT misses can occur only due to an attempt
to write memory with a guest-physical address.

Signed-off-by: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: He Chen <he.chen@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/vmx.h      |  7 +++++++
 arch/x86/include/uapi/asm/vmx.h |  2 ++
 arch/x86/kvm/vmx.c              | 45 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 55bac23..7f1b824 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -543,6 +543,13 @@ struct vmx_msr_entry {
 #define EPT_VIOLATION_GVA_TRANSLATED	(1 << EPT_VIOLATION_GVA_TRANSLATED_BIT)
 
 /*
+ * Exit Qualifications for SPPT-Induced VM Exits
+ */
+#define SPPT_INDUCED_EXIT_TYPE_BIT	11
+#define SPPT_INDUCED_EXIT_TYPE		(1 << SPPT_INDUCED_EXIT_TYPE_BIT)
+#define SPPT_INTR_INFO_UNBLOCK_NMI	INTR_INFO_UNBLOCK_NMI
+
+/*
  * VM-instruction error numbers
  */
 enum vm_instruction_error_number {
diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h
index 690a2dc..d632264 100644
--- a/arch/x86/include/uapi/asm/vmx.h
+++ b/arch/x86/include/uapi/asm/vmx.h
@@ -84,6 +84,7 @@
 #define EXIT_REASON_PML_FULL            62
 #define EXIT_REASON_XSAVES              63
 #define EXIT_REASON_XRSTORS             64
+#define EXIT_REASON_SPP                 66
 
 #define VMX_EXIT_REASONS \
 	{ EXIT_REASON_EXCEPTION_NMI,         "EXCEPTION_NMI" }, \
@@ -140,6 +141,7 @@
 	{ EXIT_REASON_ENCLS,                 "ENCLS" }, \
 	{ EXIT_REASON_RDSEED,                "RDSEED" }, \
 	{ EXIT_REASON_PML_FULL,              "PML_FULL" }, \
+	{ EXIT_REASON_SPP,                   "SPP" }, \
 	{ EXIT_REASON_XSAVES,                "XSAVES" }, \
 	{ EXIT_REASON_XRSTORS,               "XRSTORS" }
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index a4ac08a..fa4f548 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7997,6 +7997,50 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
 	return kvm_skip_emulated_instruction(vcpu);
 }
 
+static int handle_spp(struct kvm_vcpu *vcpu)
+{
+	unsigned long exit_qualification;
+
+	exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
+
+	/*
+	 * SPP VM exit happened while executing iret from NMI,
+	 * "blocked by NMI" bit has to be set before next VM entry.
+	 * There are errata that may cause this bit to not be set:
+	 * AAK134, BY25.
+	 */
+	if (!(to_vmx(vcpu)->idt_vectoring_info & VECTORING_INFO_VALID_MASK) &&
+	    (exit_qualification & SPPT_INTR_INFO_UNBLOCK_NMI))
+		vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
+			      GUEST_INTR_STATE_NMI);
+
+	pr_debug("SPP: SPP exit_qualification=%lx\n", exit_qualification);
+
+	vcpu->arch.exit_qualification = exit_qualification;
+
+	if (exit_qualification & SPPT_INDUCED_EXIT_TYPE) {
+		/*
+		 * SPPT Miss
+		 * We don't set SPP write access for the corresponding
+		 * GPA, if we haven't setup, we need to construct
+		 * SPP table here.
+		 */
+		pr_debug("SPP: %s: SPPT Miss!!!\n", __func__);
+		return 1;
+	}
+
+	/*
+	 * SPPT Misconfig
+	 * This is probably possible that your sppt table
+	 * set as an incorrect format
+	 */
+	WARN_ON(1);
+	vcpu->run->exit_reason = KVM_EXIT_UNKNOWN;
+	vcpu->run->hw.hardware_exit_reason = EXIT_REASON_SPP;
+	pr_alert("SPP: %s: SPPT Misconfiguration!!!\n", __func__);
+	return 0;
+}
+
 static int handle_pml_full(struct kvm_vcpu *vcpu)
 {
 	unsigned long exit_qualification;
@@ -8194,6 +8238,7 @@ static int (*const kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
 	[EXIT_REASON_INVVPID]                 = handle_invvpid,
 	[EXIT_REASON_RDRAND]                  = handle_invalid_op,
 	[EXIT_REASON_RDSEED]                  = handle_invalid_op,
+	[EXIT_REASON_SPP]                     = handle_spp,
 	[EXIT_REASON_XSAVES]                  = handle_xsaves,
 	[EXIT_REASON_XRSTORS]                 = handle_xrstors,
 	[EXIT_REASON_PML_FULL]		      = handle_pml_full,
-- 
2.7.4