Re: [PATCH 6/6] kvm: qemu: Enable EPT support for real mode

["Yang, Sheng" <sheng.yang@intel.com>]

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On Tuesday 22 April 2008 18:16:41 Avi Kivity wrote:
> Yang, Sheng wrote:
> > From 73c33765f3d879001818cd0719038c78a0c65561 Mon Sep 17 00:00:00 2001
> > From: Sheng Yang <sheng.yang@intel.com>
> > Date: Fri, 18 Apr 2008 17:15:39 +0800
> > Subject: [PATCH] kvm: qemu: Enable EPT support for real mode
> >
> > This patch build a identity page table on the last page of VGA bios, and
> > use it as the guest page table in nonpaging mode for EPT.
>
> Doing this in qemu means older versions of qemu can't work with an
> ept-enabled kernel.  Also, placing the table in the vga bios might
> conflict with video card assignment to a guest.
>
> Suggest placing this near the realmode tss (see vmx.c:init_rmode_tss())
> which serves a similar function.

Something like this? (along with one page reserved in e820 table)

I put the page it into 0xfffbc000 now. But I think the following implement is 
not very elegant... Too complex compared to the qemu one.

BTW: The S/R and live migration problem was fixed.

From b1836738e82ed416c8fb43cffd85b3d17ab10260 Mon Sep 17 00:00:00 2001
From: Sheng Yang <sheng.yang@intel.com>
Date: Thu, 24 Apr 2008 14:23:50 +0800
Subject: [PATCH] KVM: VMX: Perpare a identity page table for EPT in real mode


Signed-off-by: Sheng Yang <sheng.yang@intel.com>
---
 arch/x86/kvm/vmx.c         |   75 
++++++++++++++++++++++++++++++++++++++++++--
 arch/x86/kvm/vmx.h         |    3 ++
 include/asm-x86/kvm_host.h |    3 ++
 3 files changed, 78 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 588b9ea..b19b2b2 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -87,7 +87,7 @@ static inline struct vcpu_vmx *to_vmx(struct kvm_vcpu *vcpu)
 	return container_of(vcpu, struct vcpu_vmx, vcpu);
 }

-static int init_rmode_tss(struct kvm *kvm);
+static int init_rmode(struct kvm *kvm);

 static DEFINE_PER_CPU(struct vmcs *, vmxarea);
 static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
@@ -1345,7 +1345,7 @@ static void enter_rmode(struct kvm_vcpu *vcpu)
 	fix_rmode_seg(VCPU_SREG_FS, &vcpu->arch.rmode.fs);

 	kvm_mmu_reset_context(vcpu);
-	init_rmode_tss(vcpu->kvm);
+	init_rmode(vcpu->kvm);
 }

 #ifdef CONFIG_X86_64
@@ -1707,6 +1707,37 @@ out:
 	return ret;
 }

+static int init_rmode_identity_map(struct kvm *kvm)
+{
+	int i, r, ret;
+	pfn_t identity_map_pfn;
+	u32 table[PT32_ENT_PER_PAGE];
+
+	if (kvm->arch.ept_identity_pagetable_done)
+		return 1;
+	ret = 0;
+	identity_map_pfn = VMX_EPT_IDENTITY_PAGETABLE_ADDR >> PAGE_SHIFT;
+	r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE);
+	if (r < 0)
+		goto out;
+	/*
+	 * Set up identity-mapping pagetable for EPT in real mode, also verify
+	 * the contain of page
+	 * 0xe7 = _PAGE_PRESENT | _PAGE_RW | _PAGE_USER | _PAGE_ACCESSED |
+	 *	  _PAGE_DIRTY   | _PAGE_PSE
+	 */
+	for (i = 0; i < PT32_ENT_PER_PAGE; i++)
+		table[i] = (i << 22) + 0xe7;
+	r = kvm_write_guest_page(kvm, identity_map_pfn,
+			table, 0, PAGE_SIZE);
+	if (r < 0)
+		goto out;
+	kvm->arch.ept_identity_pagetable_done = true;
+	ret = 1;
+out:
+	return ret;
+}
+
 static void seg_setup(int seg)
 {
 	struct kvm_vmx_segment_field *sf = &kvm_vmx_segment_fields[seg];
@@ -1741,6 +1772,31 @@ out:
 	return r;
 }

+static int alloc_identity_pagetable(struct kvm *kvm)
+{
+	struct kvm_userspace_memory_region kvm_userspace_mem;
+	int r = 0;
+
+	down_write(&kvm->slots_lock);
+	if (kvm->arch.ept_identity_pagetable)
+		goto out;
+	kvm_userspace_mem.slot = IDENTITY_PAGETABLE_PRIVATE_MEMSLOT;
+	kvm_userspace_mem.flags = 0;
+	kvm_userspace_mem.guest_phys_addr = VMX_EPT_IDENTITY_PAGETABLE_ADDR;
+	kvm_userspace_mem.memory_size = PAGE_SIZE;
+	r = __kvm_set_memory_region(kvm, &kvm_userspace_mem, 0);
+	if (r)
+		goto out;
+
+	down_read(&current->mm->mmap_sem);
+	kvm->arch.ept_identity_pagetable = gfn_to_page(kvm,
+			VMX_EPT_IDENTITY_PAGETABLE_ADDR >> PAGE_SHIFT);
+	up_read(&current->mm->mmap_sem);
+out:
+	up_write(&kvm->slots_lock);
+	return r;
+}
+
 static void allocate_vpid(struct vcpu_vmx *vmx)
 {
 	int vpid;
@@ -1904,6 +1960,15 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
 	return 0;
 }

+static int init_rmode(struct kvm *kvm)
+{
+	if (!init_rmode_tss(kvm))
+		return 0;
+	if (!init_rmode_identity_map(kvm))
+		return 0;
+	return 1;
+}
+
 static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -1911,7 +1976,7 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
 	int ret;

 	down_read(&vcpu->kvm->slots_lock);
-	if (!init_rmode_tss(vmx->vcpu.kvm)) {
+	if (!init_rmode(vmx->vcpu.kvm)) {
 		ret = -ENOMEM;
 		goto out;
 	}
@@ -2967,6 +3032,10 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm 
*kvm, unsigned int id)
 		if (alloc_apic_access_page(kvm) != 0)
 			goto free_vmcs;

+	if (vm_need_ept())
+		if (alloc_identity_pagetable(kvm) != 0)
+			goto free_vmcs;
+
 	return &vmx->vcpu;

 free_vmcs:
diff --git a/arch/x86/kvm/vmx.h b/arch/x86/kvm/vmx.h
index 8f662e3..469a107 100644
--- a/arch/x86/kvm/vmx.h
+++ b/arch/x86/kvm/vmx.h
@@ -340,6 +340,7 @@ enum vmcs_field {
 #define MSR_IA32_FEATURE_CONTROL_VMXON_ENABLED  0x4

 #define APIC_ACCESS_PAGE_PRIVATE_MEMSLOT	9
+#define IDENTITY_PAGETABLE_PRIVATE_MEMSLOT	10

 #define VMX_NR_VPIDS				(1 << 16)
 #define VMX_VPID_EXTENT_SINGLE_CONTEXT		1
@@ -362,4 +363,6 @@ enum vmcs_field {
 #define VMX_EPT_FAKE_ACCESSED_MASK		(1ul << 62)
 #define VMX_EPT_FAKE_DIRTY_MASK			(1ul << 63)

+#define VMX_EPT_IDENTITY_PAGETABLE_ADDR		0xfffbc000ul
+
 #endif
diff --git a/include/asm-x86/kvm_host.h b/include/asm-x86/kvm_host.h
index 003bc0e..69afbab 100644
--- a/include/asm-x86/kvm_host.h
+++ b/include/asm-x86/kvm_host.h
@@ -314,6 +314,9 @@ struct kvm_arch{
 	struct page *apic_access_page;

 	gpa_t wall_clock;
+
+	struct page *ept_identity_pagetable;
+	bool ept_identity_pagetable_done;
 };

 struct kvm_vm_stat {
--
1.5.4.5

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From b1836738e82ed416c8fb43cffd85b3d17ab10260 Mon Sep 17 00:00:00 2001
From: Sheng Yang <sheng.yang@intel.com>
Date: Thu, 24 Apr 2008 14:23:50 +0800
Subject: [PATCH] KVM: VMX: Perpare a identity page table for EPT in real mode


Signed-off-by: Sheng Yang <sheng.yang@intel.com>
---
 arch/x86/kvm/vmx.c         |   75 ++++++++++++++++++++++++++++++++++++++++++--
 arch/x86/kvm/vmx.h         |    3 ++
 include/asm-x86/kvm_host.h |    3 ++
 3 files changed, 78 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 588b9ea..b19b2b2 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -87,7 +87,7 @@ static inline struct vcpu_vmx *to_vmx(struct kvm_vcpu *vcpu)
 	return container_of(vcpu, struct vcpu_vmx, vcpu);
 }
 
-static int init_rmode_tss(struct kvm *kvm);
+static int init_rmode(struct kvm *kvm);
 
 static DEFINE_PER_CPU(struct vmcs *, vmxarea);
 static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
@@ -1345,7 +1345,7 @@ static void enter_rmode(struct kvm_vcpu *vcpu)
 	fix_rmode_seg(VCPU_SREG_FS, &vcpu->arch.rmode.fs);
 
 	kvm_mmu_reset_context(vcpu);
-	init_rmode_tss(vcpu->kvm);
+	init_rmode(vcpu->kvm);
 }
 
 #ifdef CONFIG_X86_64
@@ -1707,6 +1707,37 @@ out:
 	return ret;
 }
 
+static int init_rmode_identity_map(struct kvm *kvm)
+{
+	int i, r, ret;
+	pfn_t identity_map_pfn;
+	u32 table[PT32_ENT_PER_PAGE];
+
+	if (kvm->arch.ept_identity_pagetable_done)
+		return 1;
+	ret = 0;
+	identity_map_pfn = VMX_EPT_IDENTITY_PAGETABLE_ADDR >> PAGE_SHIFT;
+	r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE);
+	if (r < 0)
+		goto out;
+	/*
+	 * Set up identity-mapping pagetable for EPT in real mode, also verify
+	 * the contain of page
+	 * 0xe7 = _PAGE_PRESENT | _PAGE_RW | _PAGE_USER | _PAGE_ACCESSED |
+	 *	  _PAGE_DIRTY   | _PAGE_PSE
+	 */
+	for (i = 0; i < PT32_ENT_PER_PAGE; i++)
+		table[i] = (i << 22) + 0xe7;
+	r = kvm_write_guest_page(kvm, identity_map_pfn,
+			table, 0, PAGE_SIZE);
+	if (r < 0)
+		goto out;
+	kvm->arch.ept_identity_pagetable_done = true;
+	ret = 1;
+out:
+	return ret;
+}
+
 static void seg_setup(int seg)
 {
 	struct kvm_vmx_segment_field *sf = &kvm_vmx_segment_fields[seg];
@@ -1741,6 +1772,31 @@ out:
 	return r;
 }
 
+static int alloc_identity_pagetable(struct kvm *kvm)
+{
+	struct kvm_userspace_memory_region kvm_userspace_mem;
+	int r = 0;
+
+	down_write(&kvm->slots_lock);
+	if (kvm->arch.ept_identity_pagetable)
+		goto out;
+	kvm_userspace_mem.slot = IDENTITY_PAGETABLE_PRIVATE_MEMSLOT;
+	kvm_userspace_mem.flags = 0;
+	kvm_userspace_mem.guest_phys_addr = VMX_EPT_IDENTITY_PAGETABLE_ADDR;
+	kvm_userspace_mem.memory_size = PAGE_SIZE;
+	r = __kvm_set_memory_region(kvm, &kvm_userspace_mem, 0);
+	if (r)
+		goto out;
+
+	down_read(&current->mm->mmap_sem);
+	kvm->arch.ept_identity_pagetable = gfn_to_page(kvm,
+			VMX_EPT_IDENTITY_PAGETABLE_ADDR >> PAGE_SHIFT);
+	up_read(&current->mm->mmap_sem);
+out:
+	up_write(&kvm->slots_lock);
+	return r;
+}
+
 static void allocate_vpid(struct vcpu_vmx *vmx)
 {
 	int vpid;
@@ -1904,6 +1960,15 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
 	return 0;
 }
 
+static int init_rmode(struct kvm *kvm)
+{
+	if (!init_rmode_tss(kvm))
+		return 0;
+	if (!init_rmode_identity_map(kvm))
+		return 0;
+	return 1;
+}
+
 static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -1911,7 +1976,7 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
 	int ret;
 
 	down_read(&vcpu->kvm->slots_lock);
-	if (!init_rmode_tss(vmx->vcpu.kvm)) {
+	if (!init_rmode(vmx->vcpu.kvm)) {
 		ret = -ENOMEM;
 		goto out;
 	}
@@ -2967,6 +3032,10 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 		if (alloc_apic_access_page(kvm) != 0)
 			goto free_vmcs;
 
+	if (vm_need_ept())
+		if (alloc_identity_pagetable(kvm) != 0)
+			goto free_vmcs;
+
 	return &vmx->vcpu;
 
 free_vmcs:
diff --git a/arch/x86/kvm/vmx.h b/arch/x86/kvm/vmx.h
index 8f662e3..469a107 100644
--- a/arch/x86/kvm/vmx.h
+++ b/arch/x86/kvm/vmx.h
@@ -340,6 +340,7 @@ enum vmcs_field {
 #define MSR_IA32_FEATURE_CONTROL_VMXON_ENABLED  0x4
 
 #define APIC_ACCESS_PAGE_PRIVATE_MEMSLOT	9
+#define IDENTITY_PAGETABLE_PRIVATE_MEMSLOT	10
 
 #define VMX_NR_VPIDS				(1 << 16)
 #define VMX_VPID_EXTENT_SINGLE_CONTEXT		1
@@ -362,4 +363,6 @@ enum vmcs_field {
 #define VMX_EPT_FAKE_ACCESSED_MASK		(1ul << 62)
 #define VMX_EPT_FAKE_DIRTY_MASK			(1ul << 63)
 
+#define VMX_EPT_IDENTITY_PAGETABLE_ADDR		0xfffbc000ul
+
 #endif
diff --git a/include/asm-x86/kvm_host.h b/include/asm-x86/kvm_host.h
index 003bc0e..69afbab 100644
--- a/include/asm-x86/kvm_host.h
+++ b/include/asm-x86/kvm_host.h
@@ -314,6 +314,9 @@ struct kvm_arch{
 	struct page *apic_access_page;
 
 	gpa_t wall_clock;
+
+	struct page *ept_identity_pagetable;
+	bool ept_identity_pagetable_done;
 };
 
 struct kvm_vm_stat {
-- 
1.5.4.5


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