[PATCH KVM VMX 0/2] Enable Unrestricted Guest

[PATCH KVM VMX 0/2] Enable Unrestricted Guest

[Nitin A Kamble]

Hi Avi,
  I have modified the earlier patch as per you comments. I have prepared a 
separate patch for renaming rmode.active to rmode.vm86_active. And 2nd patch 
enables the Unrestricted Guest feature in the KVM.
   This patch will also work with unfixed (cpu reset state) qemu. 
Please apply.

Thanks & Regards,
Nitin

Nitin A Kamble (2):
  KVM: VMX: Rename rmode.active to rmode.vm86_active
  KVM: VMX: Support Unrestricted Guest feature

 arch/x86/include/asm/kvm_host.h |   14 ++++---
 arch/x86/include/asm/vmx.h      |    1 +
 arch/x86/kvm/vmx.c              |   77 +++++++++++++++++++++++++++++----------
 3 files changed, 66 insertions(+), 26 deletions(-)

[PATCH KVM VMX 1/2] KVM: VMX: Rename rmode.active to rmode.vm86_active

[Nitin A Kamble]

That way the interpretation of rmode.active becomes more clear with
unrestricted guest code.

Signed-off-by: Nitin A Kamble <nitin.a.kamble@intel.com>
---
 arch/x86/include/asm/kvm_host.h |    2 +-
 arch/x86/kvm/vmx.c              |   28 ++++++++++++++--------------
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1951d39..1cc901e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -339,7 +339,7 @@ struct kvm_vcpu_arch {
 	} interrupt;
 
 	struct {
-		int active;
+		int vm86_active;
 		u8 save_iopl;
 		struct kvm_save_segment {
 			u16 selector;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index fd05fd2..d1ec8a9 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -497,7 +497,7 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu)
 		if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP)
 			eb |= 1u << BP_VECTOR;
 	}
-	if (vcpu->arch.rmode.active)
+	if (vcpu->arch.rmode.vm86_active)
 		eb = ~0;
 	if (enable_ept)
 		eb &= ~(1u << PF_VECTOR); /* bypass_guest_pf = 0 */
@@ -733,7 +733,7 @@ static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu)
 
 static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
 {
-	if (vcpu->arch.rmode.active)
+	if (vcpu->arch.rmode.vm86_active)
 		rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM;
 	vmcs_writel(GUEST_RFLAGS, rflags);
 }
@@ -790,7 +790,7 @@ static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
 		intr_info |= INTR_INFO_DELIVER_CODE_MASK;
 	}
 
-	if (vcpu->arch.rmode.active) {
+	if (vcpu->arch.rmode.vm86_active) {
 		vmx->rmode.irq.pending = true;
 		vmx->rmode.irq.vector = nr;
 		vmx->rmode.irq.rip = kvm_rip_read(vcpu);
@@ -1370,7 +1370,7 @@ static void enter_pmode(struct kvm_vcpu *vcpu)
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
 	vmx->emulation_required = 1;
-	vcpu->arch.rmode.active = 0;
+	vcpu->arch.rmode.vm86_active = 0;
 
 	vmcs_writel(GUEST_TR_BASE, vcpu->arch.rmode.tr.base);
 	vmcs_write32(GUEST_TR_LIMIT, vcpu->arch.rmode.tr.limit);
@@ -1432,7 +1432,7 @@ static void enter_rmode(struct kvm_vcpu *vcpu)
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
 	vmx->emulation_required = 1;
-	vcpu->arch.rmode.active = 1;
+	vcpu->arch.rmode.vm86_active = 1;
 
 	vcpu->arch.rmode.tr.base = vmcs_readl(GUEST_TR_BASE);
 	vmcs_writel(GUEST_TR_BASE, rmode_tss_base(vcpu->kvm));
@@ -1616,10 +1616,10 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 
 	vmx_fpu_deactivate(vcpu);
 
-	if (vcpu->arch.rmode.active && (cr0 & X86_CR0_PE))
+	if (vcpu->arch.rmode.vm86_active && (cr0 & X86_CR0_PE))
 		enter_pmode(vcpu);
 
-	if (!vcpu->arch.rmode.active && !(cr0 & X86_CR0_PE))
+	if (!vcpu->arch.rmode.vm86_active && !(cr0 & X86_CR0_PE))
 		enter_rmode(vcpu);
 
 #ifdef CONFIG_X86_64
@@ -1675,7 +1675,7 @@ static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 
 static void vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 {
-	unsigned long hw_cr4 = cr4 | (vcpu->arch.rmode.active ?
+	unsigned long hw_cr4 = cr4 | (vcpu->arch.rmode.vm86_active ?
 		    KVM_RMODE_VM_CR4_ALWAYS_ON : KVM_PMODE_VM_CR4_ALWAYS_ON);
 
 	vcpu->arch.cr4 = cr4;
@@ -1758,7 +1758,7 @@ static void vmx_set_segment(struct kvm_vcpu *vcpu,
 	struct kvm_vmx_segment_field *sf = &kvm_vmx_segment_fields[seg];
 	u32 ar;
 
-	if (vcpu->arch.rmode.active && seg == VCPU_SREG_TR) {
+	if (vcpu->arch.rmode.vm86_active && seg == VCPU_SREG_TR) {
 		vcpu->arch.rmode.tr.selector = var->selector;
 		vcpu->arch.rmode.tr.base = var->base;
 		vcpu->arch.rmode.tr.limit = var->limit;
@@ -1768,7 +1768,7 @@ static void vmx_set_segment(struct kvm_vcpu *vcpu,
 	vmcs_writel(sf->base, var->base);
 	vmcs_write32(sf->limit, var->limit);
 	vmcs_write16(sf->selector, var->selector);
-	if (vcpu->arch.rmode.active && var->s) {
+	if (vcpu->arch.rmode.vm86_active && var->s) {
 		/*
 		 * Hack real-mode segments into vm86 compatibility.
 		 */
@@ -2337,7 +2337,7 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
 		goto out;
 	}
 
-	vmx->vcpu.arch.rmode.active = 0;
+	vmx->vcpu.arch.rmode.vm86_active = 0;
 
 	vmx->soft_vnmi_blocked = 0;
 
@@ -2475,7 +2475,7 @@ static void vmx_inject_irq(struct kvm_vcpu *vcpu)
 	KVMTRACE_1D(INJ_VIRQ, vcpu, (u32)irq, handler);
 
 	++vcpu->stat.irq_injections;
-	if (vcpu->arch.rmode.active) {
+	if (vcpu->arch.rmode.vm86_active) {
 		vmx->rmode.irq.pending = true;
 		vmx->rmode.irq.vector = irq;
 		vmx->rmode.irq.rip = kvm_rip_read(vcpu);
@@ -2516,7 +2516,7 @@ static void vmx_inject_nmi(struct kvm_vcpu *vcpu)
 	}
 
 	++vcpu->stat.nmi_injections;
-	if (vcpu->arch.rmode.active) {
+	if (vcpu->arch.rmode.vm86_active) {
 		vmx->rmode.irq.pending = true;
 		vmx->rmode.irq.vector = NMI_VECTOR;
 		vmx->rmode.irq.rip = kvm_rip_read(vcpu);
@@ -2652,7 +2652,7 @@ static int handle_exception(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 		return kvm_mmu_page_fault(vcpu, cr2, error_code);
 	}
 
-	if (vcpu->arch.rmode.active &&
+	if (vcpu->arch.rmode.vm86_active &&
 	    handle_rmode_exception(vcpu, intr_info & INTR_INFO_VECTOR_MASK,
 								error_code)) {
 		if (vcpu->arch.halt_request) {
-- 
1.6.0.6

Re: [PATCH KVM VMX 1/2] KVM: VMX: Rename rmode.active to rmode.vm86_active

[Avi Kivity]

Nitin A Kamble wrote:
> That way the interpretation of rmode.active becomes more clear with
> unrestricted guest code.
>   

Applied, thanks.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

[PATCH KVM VMX 2/2] KVM: VMX: Support Unrestricted Guest feature

[Nitin A Kamble]

"Unrestricted Guest" feature is added in the VMX specification.
Intel Westmere and onwards processors will support this feature.

    It allows kvm guests to run real mode and unpaged mode
code natively in the VMX mode when EPT is turned on. With the
unrestricted guest there is no need to emulate the guest real mode code
in the vm86 container or in the emulator. Also the guest big real mode
code works like native.

  The attached patch enhances KVM to use the unrestricted guest feature
if available on the processor. It also adds a new kernel/module
parameter to disable the unrestricted guest feature at the boot time.

Signed-off-by: Nitin A Kamble <nitin.a.kamble@intel.com>
---
 arch/x86/include/asm/kvm_host.h |   12 +++++----
 arch/x86/include/asm/vmx.h      |    1 +
 arch/x86/kvm/vmx.c              |   49 ++++++++++++++++++++++++++++++++++----
 3 files changed, 51 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1cc901e..a1a96a5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -37,12 +37,14 @@
 #define CR3_L_MODE_RESERVED_BITS (CR3_NONPAE_RESERVED_BITS |	\
 				  0xFFFFFF0000000000ULL)
 
-#define KVM_GUEST_CR0_MASK				   \
-	(X86_CR0_PG | X86_CR0_PE | X86_CR0_WP | X86_CR0_NE \
-	 | X86_CR0_NW | X86_CR0_CD)
+#define KVM_GUEST_CR0_MASK_UNRESTRICTED_GUEST				\
+	(X86_CR0_WP | X86_CR0_NE | X86_CR0_NW | X86_CR0_CD)
+#define KVM_GUEST_CR0_MASK						\
+	(KVM_GUEST_CR0_MASK_UNRESTRICTED_GUEST | X86_CR0_PG | X86_CR0_PE)
+#define KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST				\
+	(X86_CR0_WP | X86_CR0_NE | X86_CR0_TS | X86_CR0_MP)
 #define KVM_VM_CR0_ALWAYS_ON						\
-	(X86_CR0_PG | X86_CR0_PE | X86_CR0_WP | X86_CR0_NE | X86_CR0_TS \
-	 | X86_CR0_MP)
+	(KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST | X86_CR0_PG | X86_CR0_PE)
 #define KVM_GUEST_CR4_MASK						\
 	(X86_CR4_VME | X86_CR4_PSE | X86_CR4_PAE | X86_CR4_PGE | X86_CR4_VMXE)
 #define KVM_PMODE_VM_CR4_ALWAYS_ON (X86_CR4_PAE | X86_CR4_VMXE)
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 498f944..c73da02 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -55,6 +55,7 @@
 #define SECONDARY_EXEC_ENABLE_EPT               0x00000002
 #define SECONDARY_EXEC_ENABLE_VPID              0x00000020
 #define SECONDARY_EXEC_WBINVD_EXITING		0x00000040
+#define SECONDARY_EXEC_UNRESTRICTED_GUEST	0x00000080
 
 
 #define PIN_BASED_EXT_INTR_MASK                 0x00000001
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d1ec8a9..b3d8a3a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -50,6 +50,10 @@ module_param_named(flexpriority, flexpriority_enabled, bool, S_IRUGO);
 static int __read_mostly enable_ept = 1;
 module_param_named(ept, enable_ept, bool, S_IRUGO);
 
+static int __read_mostly enable_unrestricted_guest = 1;
+module_param_named(unrestricted_guest,
+			enable_unrestricted_guest, bool, S_IRUGO);
+
 static int __read_mostly emulate_invalid_guest_state = 0;
 module_param(emulate_invalid_guest_state, bool, S_IRUGO);
 
@@ -270,6 +274,12 @@ static inline int cpu_has_vmx_ept(void)
 		SECONDARY_EXEC_ENABLE_EPT;
 }
 
+static inline int cpu_has_vmx_unrestricted_guest(void)
+{
+	return vmcs_config.cpu_based_2nd_exec_ctrl &
+		SECONDARY_EXEC_UNRESTRICTED_GUEST;
+}
+
 static inline int vm_need_virtualize_apic_accesses(struct kvm *kvm)
 {
 	return flexpriority_enabled &&
@@ -1201,7 +1211,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
 		opt2 = SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
 			SECONDARY_EXEC_WBINVD_EXITING |
 			SECONDARY_EXEC_ENABLE_VPID |
-			SECONDARY_EXEC_ENABLE_EPT;
+			SECONDARY_EXEC_ENABLE_EPT |
+			SECONDARY_EXEC_UNRESTRICTED_GUEST;
 		if (adjust_vmx_controls(min2, opt2,
 					MSR_IA32_VMX_PROCBASED_CTLS2,
 					&_cpu_based_2nd_exec_control) < 0)
@@ -1331,8 +1342,13 @@ static __init int hardware_setup(void)
 	if (!cpu_has_vmx_vpid())
 		enable_vpid = 0;
 
-	if (!cpu_has_vmx_ept())
+	if (!cpu_has_vmx_ept()) {
 		enable_ept = 0;
+		enable_unrestricted_guest = 0;
+	}
+
+	if (!cpu_has_vmx_unrestricted_guest())
+		enable_unrestricted_guest = 0;
 
 	if (!cpu_has_vmx_flexpriority())
 		flexpriority_enabled = 0;
@@ -1431,6 +1447,9 @@ static void enter_rmode(struct kvm_vcpu *vcpu)
 	unsigned long flags;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
+	if (enable_unrestricted_guest)
+		goto continue_rmode;
+
 	vmx->emulation_required = 1;
 	vcpu->arch.rmode.vm86_active = 1;
 
@@ -1584,7 +1603,6 @@ static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
 			      CPU_BASED_CR3_STORE_EXITING));
 		vcpu->arch.cr0 = cr0;
 		vmx_set_cr4(vcpu, vcpu->arch.cr4);
-		*hw_cr0 |= X86_CR0_PE | X86_CR0_PG;
 		*hw_cr0 &= ~X86_CR0_WP;
 	} else if (!is_paging(vcpu)) {
 		/* From nonpaging to paging */
@@ -1611,8 +1629,13 @@ static void ept_update_paging_mode_cr4(unsigned long *hw_cr4,
 
 static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 {
-	unsigned long hw_cr0 = (cr0 & ~KVM_GUEST_CR0_MASK) |
-				KVM_VM_CR0_ALWAYS_ON;
+	unsigned long hw_cr0;
+
+	if (enable_unrestricted_guest)
+		hw_cr0 = (cr0 & ~KVM_GUEST_CR0_MASK_UNRESTRICTED_GUEST)
+			| KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST;
+	else
+		hw_cr0 = (cr0 & ~KVM_GUEST_CR0_MASK) | KVM_VM_CR0_ALWAYS_ON;
 
 	vmx_fpu_deactivate(vcpu);
 
@@ -1777,6 +1800,10 @@ static void vmx_set_segment(struct kvm_vcpu *vcpu,
 		ar = 0xf3;
 	} else
 		ar = vmx_segment_access_rights(var);
+
+	if (enable_unrestricted_guest && (seg != VCPU_SREG_LDTR))
+		ar |= 0x1; /* Accessed */
+
 	vmcs_write32(sf->ar_bytes, ar);
 }
 
@@ -2073,11 +2100,19 @@ out:
 static void seg_setup(int seg)
 {
 	struct kvm_vmx_segment_field *sf = &kvm_vmx_segment_fields[seg];
+	unsigned int ar;
 
 	vmcs_write16(sf->selector, 0);
 	vmcs_writel(sf->base, 0);
 	vmcs_write32(sf->limit, 0xffff);
-	vmcs_write32(sf->ar_bytes, 0xf3);
+	if (enable_unrestricted_guest) {
+		ar = 0x93;
+		if (seg == VCPU_SREG_CS)
+			ar |= 0x08; /* code segment */
+	} else
+		ar = 0xf3;
+
+	vmcs_write32(sf->ar_bytes, ar);
 }
 
 static int alloc_apic_access_page(struct kvm *kvm)
@@ -2220,6 +2255,8 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
 			exec_control &= ~SECONDARY_EXEC_ENABLE_VPID;
 		if (!enable_ept)
 			exec_control &= ~SECONDARY_EXEC_ENABLE_EPT;
+		if (!enable_unrestricted_guest)
+			exec_control &= ~SECONDARY_EXEC_UNRESTRICTED_GUEST;
 		vmcs_write32(SECONDARY_VM_EXEC_CONTROL, exec_control);
 	}
 
-- 
1.6.0.6

Re: [PATCH KVM VMX 2/2] KVM: VMX: Support Unrestricted Guest feature

[Avi Kivity]

Nitin A Kamble wrote:
> "Unrestricted Guest" feature is added in the VMX specification.
> Intel Westmere and onwards processors will support this feature.
>
>     It allows kvm guests to run real mode and unpaged mode
> code natively in the VMX mode when EPT is turned on. With the
> unrestricted guest there is no need to emulate the guest real mode code
> in the vm86 container or in the emulator. Also the guest big real mode
> code works like native.
>
>   The attached patch enhances KVM to use the unrestricted guest feature
> if available on the processor. It also adds a new kernel/module
> parameter to disable the unrestricted guest feature at the boot time.
>
>  
> @@ -1431,6 +1447,9 @@ static void enter_rmode(struct kvm_vcpu *vcpu)
>  	unsigned long flags;
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>  
> +	if (enable_unrestricted_guest)
> +		goto continue_rmode;
> +
>   

I think you should just return here.  You don't need to reset the mmu 
context or run the init_rmode() code.  Maybe you need to flush the tlb.



> +
> +	if (enable_unrestricted_guest && (seg != VCPU_SREG_LDTR))
> +		ar |= 0x1; /* Accessed */
> +
>  	vmcs_write32(sf->ar_bytes, ar);
>  }
>   

Please add a comment indicating it's for broken userspace that doesn't 
set the A bit.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

[PATCH] KVM: VMX: Support Unrestricted Guest feature

[Nitin A Kamble]

"Unrestricted Guest" feature is added in the VMX specification.
Intel Westmere and onwards processors will support this feature.

    It allows kvm guests to run real mode and unpaged mode
code natively in the VMX mode when EPT is turned on. With the
unrestricted guest there is no need to emulate the guest real mode code
in the vm86 container or in the emulator. Also the guest big real mode
code works like native.

  The attached patch enhances KVM to use the unrestricted guest feature
if available on the processor. It also adds a new kernel/module
parameter to disable the unrestricted guest feature at the boot time.

Signed-off-by: Nitin A Kamble <nitin.a.kamble@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
 arch/x86/include/asm/kvm_host.h |   12 ++++---
 arch/x86/include/asm/vmx.h      |    1 +
 arch/x86/kvm/vmx.c              |   60 +++++++++++++++++++++++++++++++++++----
 3 files changed, 62 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1cc901e..a1a96a5 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -37,12 +37,14 @@
 #define CR3_L_MODE_RESERVED_BITS (CR3_NONPAE_RESERVED_BITS |	\
 				  0xFFFFFF0000000000ULL)
 
-#define KVM_GUEST_CR0_MASK				   \
-	(X86_CR0_PG | X86_CR0_PE | X86_CR0_WP | X86_CR0_NE \
-	 | X86_CR0_NW | X86_CR0_CD)
+#define KVM_GUEST_CR0_MASK_UNRESTRICTED_GUEST				\
+	(X86_CR0_WP | X86_CR0_NE | X86_CR0_NW | X86_CR0_CD)
+#define KVM_GUEST_CR0_MASK						\
+	(KVM_GUEST_CR0_MASK_UNRESTRICTED_GUEST | X86_CR0_PG | X86_CR0_PE)
+#define KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST				\
+	(X86_CR0_WP | X86_CR0_NE | X86_CR0_TS | X86_CR0_MP)
 #define KVM_VM_CR0_ALWAYS_ON						\
-	(X86_CR0_PG | X86_CR0_PE | X86_CR0_WP | X86_CR0_NE | X86_CR0_TS \
-	 | X86_CR0_MP)
+	(KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST | X86_CR0_PG | X86_CR0_PE)
 #define KVM_GUEST_CR4_MASK						\
 	(X86_CR4_VME | X86_CR4_PSE | X86_CR4_PAE | X86_CR4_PGE | X86_CR4_VMXE)
 #define KVM_PMODE_VM_CR4_ALWAYS_ON (X86_CR4_PAE | X86_CR4_VMXE)
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 11be5ad..e7927a6 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -55,6 +55,7 @@
 #define SECONDARY_EXEC_ENABLE_EPT               0x00000002
 #define SECONDARY_EXEC_ENABLE_VPID              0x00000020
 #define SECONDARY_EXEC_WBINVD_EXITING		0x00000040
+#define SECONDARY_EXEC_UNRESTRICTED_GUEST	0x00000080
 
 
 #define PIN_BASED_EXT_INTR_MASK                 0x00000001
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 2c454ea..fb14bde 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -51,6 +51,10 @@ module_param_named(flexpriority, flexpriority_enabled, bool, S_IRUGO);
 static int __read_mostly enable_ept = 1;
 module_param_named(ept, enable_ept, bool, S_IRUGO);
 
+static int __read_mostly enable_unrestricted_guest = 1;
+module_param_named(unrestricted_guest,
+			enable_unrestricted_guest, bool, S_IRUGO);
+
 static int __read_mostly emulate_invalid_guest_state = 0;
 module_param(emulate_invalid_guest_state, bool, S_IRUGO);
 
@@ -279,6 +283,12 @@ static inline int cpu_has_vmx_ept(void)
 		SECONDARY_EXEC_ENABLE_EPT;
 }
 
+static inline int cpu_has_vmx_unrestricted_guest(void)
+{
+	return vmcs_config.cpu_based_2nd_exec_ctrl &
+		SECONDARY_EXEC_UNRESTRICTED_GUEST;
+}
+
 static inline int vm_need_virtualize_apic_accesses(struct kvm *kvm)
 {
 	return flexpriority_enabled &&
@@ -1210,7 +1220,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
 		opt2 = SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
 			SECONDARY_EXEC_WBINVD_EXITING |
 			SECONDARY_EXEC_ENABLE_VPID |
-			SECONDARY_EXEC_ENABLE_EPT;
+			SECONDARY_EXEC_ENABLE_EPT |
+			SECONDARY_EXEC_UNRESTRICTED_GUEST;
 		if (adjust_vmx_controls(min2, opt2,
 					MSR_IA32_VMX_PROCBASED_CTLS2,
 					&_cpu_based_2nd_exec_control) < 0)
@@ -1340,8 +1351,13 @@ static __init int hardware_setup(void)
 	if (!cpu_has_vmx_vpid())
 		enable_vpid = 0;
 
-	if (!cpu_has_vmx_ept())
+	if (!cpu_has_vmx_ept()) {
 		enable_ept = 0;
+		enable_unrestricted_guest = 0;
+	}
+
+	if (!cpu_has_vmx_unrestricted_guest())
+		enable_unrestricted_guest = 0;
 
 	if (!cpu_has_vmx_flexpriority())
 		flexpriority_enabled = 0;
@@ -1440,6 +1456,9 @@ static void enter_rmode(struct kvm_vcpu *vcpu)
 	unsigned long flags;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
+	if (enable_unrestricted_guest)
+		return;
+
 	vmx->emulation_required = 1;
 	vcpu->arch.rmode.vm86_active = 1;
 
@@ -1593,7 +1612,6 @@ static void ept_update_paging_mode_cr0(unsigned long *hw_cr0,
 			      CPU_BASED_CR3_STORE_EXITING));
 		vcpu->arch.cr0 = cr0;
 		vmx_set_cr4(vcpu, vcpu->arch.cr4);
-		*hw_cr0 |= X86_CR0_PE | X86_CR0_PG;
 		*hw_cr0 &= ~X86_CR0_WP;
 	} else if (!is_paging(vcpu)) {
 		/* From nonpaging to paging */
@@ -1620,8 +1638,13 @@ static void ept_update_paging_mode_cr4(unsigned long *hw_cr4,
 
 static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 {
-	unsigned long hw_cr0 = (cr0 & ~KVM_GUEST_CR0_MASK) |
-				KVM_VM_CR0_ALWAYS_ON;
+	unsigned long hw_cr0;
+
+	if (enable_unrestricted_guest)
+		hw_cr0 = (cr0 & ~KVM_GUEST_CR0_MASK_UNRESTRICTED_GUEST)
+			| KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST;
+	else
+		hw_cr0 = (cr0 & ~KVM_GUEST_CR0_MASK) | KVM_VM_CR0_ALWAYS_ON;
 
 	vmx_fpu_deactivate(vcpu);
 
@@ -1786,6 +1809,21 @@ static void vmx_set_segment(struct kvm_vcpu *vcpu,
 		ar = 0xf3;
 	} else
 		ar = vmx_segment_access_rights(var);
+
+	/*
+	 *   Fix the "Accessed" bit in AR field of segment registers for older
+	 * qemu binaries.
+	 *   IA32 arch specifies that at the time of processor reset the
+	 * "Accessed" bit in the AR field of segment registers is 1. And qemu
+	 * is setting it to 0 in the usedland code. This causes invalid guest
+	 * state vmexit when "unrestricted guest" mode is turned on.
+	 *    Fix for this setup issue in cpu_reset is being pushed in the qemu
+	 * tree. Newer qemu binaries with that qemu fix would not need this
+	 * kvm hack.
+	 */
+	if (enable_unrestricted_guest && (seg != VCPU_SREG_LDTR))
+		ar |= 0x1; /* Accessed */
+
 	vmcs_write32(sf->ar_bytes, ar);
 }
 
@@ -2082,11 +2120,19 @@ out:
 static void seg_setup(int seg)
 {
 	struct kvm_vmx_segment_field *sf = &kvm_vmx_segment_fields[seg];
+	unsigned int ar;
 
 	vmcs_write16(sf->selector, 0);
 	vmcs_writel(sf->base, 0);
 	vmcs_write32(sf->limit, 0xffff);
-	vmcs_write32(sf->ar_bytes, 0xf3);
+	if (enable_unrestricted_guest) {
+		ar = 0x93;
+		if (seg == VCPU_SREG_CS)
+			ar |= 0x08; /* code segment */
+	} else
+		ar = 0xf3;
+
+	vmcs_write32(sf->ar_bytes, ar);
 }
 
 static int alloc_apic_access_page(struct kvm *kvm)
@@ -2229,6 +2275,8 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
 			exec_control &= ~SECONDARY_EXEC_ENABLE_VPID;
 		if (!enable_ept)
 			exec_control &= ~SECONDARY_EXEC_ENABLE_EPT;
+		if (!enable_unrestricted_guest)
+			exec_control &= ~SECONDARY_EXEC_UNRESTRICTED_GUEST;
 		vmcs_write32(SECONDARY_VM_EXEC_CONTROL, exec_control);
 	}
 
-- 
1.6.0.6

Re: [PATCH] KVM: VMX: Support Unrestricted Guest feature

[Avi Kivity]

Nitin A Kamble wrote:
> "Unrestricted Guest" feature is added in the VMX specification.
> Intel Westmere and onwards processors will support this feature.
>
>     It allows kvm guests to run real mode and unpaged mode
> code natively in the VMX mode when EPT is turned on. With the
> unrestricted guest there is no need to emulate the guest real mode code
> in the vm86 container or in the emulator. Also the guest big real mode
> code works like native.
>
>   The attached patch enhances KVM to use the unrestricted guest feature
> if available on the processor. It also adds a new kernel/module
> parameter to disable the unrestricted guest feature at the boot time.
>
>   

Applied, thanks.

-- 
error compiling committee.c: too many arguments to function