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Subject[RFC PATCH V2 06/11] KVM: VMX: Introduce SPP-Induced vm exit and it's handle.
Date
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 <yi.z.zhang@linux.intel.com>
Signed-off-by: He Chen <he.chen@linux.intel.com>
---
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 bd4ec8a..ee24eb2 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -539,6 +539,13 @@ 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 f0b0c90..ac67622 100644
--- a/arch/x86/include/uapi/asm/vmx.h
+++ b/arch/x86/include/uapi/asm/vmx.h
@@ -85,6 +85,7 @@
#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" }, \
@@ -141,6 +142,7 @@
{ 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 e96b4c7..6634098 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -9698,6 +9698,50 @@ static int handle_invpcid(struct kvm_vcpu *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 a 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;
@@ -9910,6 +9954,7 @@ 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
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