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[RFC PATCH 3/4] KVM: x86: add support for emulating UMIP

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  [RFC PATCH 3/4] KVM: x86: add support for emulating UMIP Paolo Bonzini <pbonzini@redhat.com> - 2016-07-12 21:30 +0200
    Re: [RFC PATCH 3/4] KVM: x86: add support for emulating UMIP Radim Krčmář <rkrcmar@redhat.com> - 2016-07-13 22:10 +0200
      Re: [RFC PATCH 3/4] KVM: x86: add support for emulating UMIP Paolo Bonzini <pbonzini@redhat.com> - 2016-07-14 09:10 +0200
        Re: [RFC PATCH 3/4] KVM: x86: add support for emulating UMIP Radim Krčmář <rkrcmar@redhat.com> - 2016-07-14 14:30 +0200

#1441677 — [RFC PATCH 3/4] KVM: x86: add support for emulating UMIP

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/include/asm/kvm_host.h |  3 ++-
 arch/x86/kvm/cpuid.c            |  5 ++++-
 arch/x86/kvm/cpuid.h            |  8 ++++++++
 arch/x86/kvm/emulate.c          | 13 +++++++++++++
 arch/x86/kvm/svm.c              |  6 ++++++
 arch/x86/kvm/vmx.c              |  6 ++++++
 arch/x86/kvm/x86.c              |  3 +++
 7 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d8204817a5fe..9e1a1db65c7b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -86,7 +86,7 @@
 			  | X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR | X86_CR4_PCIDE \
 			  | X86_CR4_OSXSAVE | X86_CR4_SMEP | X86_CR4_FSGSBASE \
 			  | X86_CR4_OSXMMEXCPT | X86_CR4_VMXE | X86_CR4_SMAP \
-			  | X86_CR4_PKE))
+			  | X86_CR4_PKE | X86_CR4_UMIP))
 
 #define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)
 
@@ -971,6 +971,7 @@ struct kvm_x86_ops {
 	void (*handle_external_intr)(struct kvm_vcpu *vcpu);
 	bool (*mpx_supported)(void);
 	bool (*xsaves_supported)(void);
+	bool (*umip_emulated)(void);
 
 	int (*check_nested_events)(struct kvm_vcpu *vcpu, bool external_intr);
 
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 7597b42a8a88..ac80e74056c4 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -315,6 +315,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 	unsigned f_invpcid = kvm_x86_ops->invpcid_supported() ? F(INVPCID) : 0;
 	unsigned f_mpx = kvm_mpx_supported() ? F(MPX) : 0;
 	unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0;
+	unsigned f_umip = kvm_x86_ops->umip_emulated() ? F(UMIP) : 0;
 
 	/* cpuid 1.edx */
 	const u32 kvm_cpuid_1_edx_x86_features =
@@ -373,7 +374,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 		F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | f_xsaves;
 
 	/* cpuid 7.0.ecx*/
-	const u32 kvm_cpuid_7_0_ecx_x86_features = F(PKU) | 0 /*OSPKE*/;
+	const u32 kvm_cpuid_7_0_ecx_x86_features = F(PKU) | 0 /*OSPKE*/ |
+		F(UMIP);
 
 	/* all calls to cpuid_count() should be made on the same cpu */
 	get_cpu();
@@ -454,6 +456,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 			entry->ebx |= F(TSC_ADJUST);
 			entry->ecx &= kvm_cpuid_7_0_ecx_x86_features;
 			cpuid_mask(&entry->ecx, CPUID_7_ECX);
+			entry->ecx |= f_umip;
 			/* PKU is not yet implemented for shadow paging. */
 			if (!tdp_enabled)
 				entry->ecx &= ~F(PKU);
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index e17a74b1d852..422de9db1785 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -88,6 +88,14 @@ static inline bool guest_cpuid_has_pku(struct kvm_vcpu *vcpu)
 	return best && (best->ecx & bit(X86_FEATURE_PKU));
 }
 
+static inline bool guest_cpuid_has_umip(struct kvm_vcpu *vcpu)
+{
+	struct kvm_cpuid_entry2 *best;
+
+	best = kvm_find_cpuid_entry(vcpu, 7, 0);
+	return best && (best->ecx & bit(X86_FEATURE_UMIP));
+}
+
 static inline bool guest_cpuid_has_longmode(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpuid_entry2 *best;
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 3e09c7461ba8..d2f568a0fc46 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3579,6 +3579,11 @@ static int em_rdmsr(struct x86_emulate_ctxt *ctxt)
 
 static int em_store_sreg(struct x86_emulate_ctxt *ctxt, int segment)
 {
+	if (segment > VCPU_SREG_GS &&
+	    (ctxt->ops->get_cr(ctxt, 4) & X86_CR4_UMIP) &&
+	    ctxt->ops->cpl(ctxt) > 0)
+		return emulate_gp(ctxt, 0);
+
 	ctxt->dst.val = get_segment_selector(ctxt, segment);
 	if (ctxt->dst.bytes == 4 && ctxt->dst.type == OP_MEM)
 		ctxt->dst.bytes = 2;
@@ -3679,6 +3684,10 @@ static int emulate_store_desc_ptr(struct x86_emulate_ctxt *ctxt,
 {
 	struct desc_ptr desc_ptr;
 
+	if ((ctxt->ops->get_cr(ctxt, 4) & X86_CR4_UMIP) &&
+	    ctxt->ops->cpl(ctxt) > 0)
+		return emulate_gp(ctxt, 0);
+
 	if (ctxt->mode == X86EMUL_MODE_PROT64)
 		ctxt->op_bytes = 8;
 	get(ctxt, &desc_ptr);
@@ -3738,6 +3747,10 @@ static int em_lidt(struct x86_emulate_ctxt *ctxt)
 
 static int em_smsw(struct x86_emulate_ctxt *ctxt)
 {
+	if ((ctxt->ops->get_cr(ctxt, 4) & X86_CR4_UMIP) &&
+	    ctxt->ops->cpl(ctxt) > 0)
+		return emulate_gp(ctxt, 0);
+
 	if (ctxt->dst.type == OP_MEM)
 		ctxt->dst.bytes = 2;
 	ctxt->dst.val = ctxt->ops->get_cr(ctxt, 0);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 5bfdbbf1ce79..227258ddab24 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4736,6 +4736,11 @@ static bool svm_xsaves_supported(void)
 	return false;
 }
 
+static bool svm_umip_emulated(void)
+{
+	return false;
+}
+
 static bool svm_has_wbinvd_exit(void)
 {
 	return true;
@@ -5054,6 +5059,7 @@ static struct kvm_x86_ops svm_x86_ops = {
 	.invpcid_supported = svm_invpcid_supported,
 	.mpx_supported = svm_mpx_supported,
 	.xsaves_supported = svm_xsaves_supported,
+	.umip_emulated = svm_umip_emulated,
 
 	.set_supported_cpuid = svm_set_supported_cpuid,
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index a9e35b3f3ea6..b133fc3d6a7d 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8595,6 +8595,11 @@ static bool vmx_xsaves_supported(void)
 		SECONDARY_EXEC_XSAVES;
 }
 
+static bool vmx_umip_emulated(void)
+{
+	return false;
+}
+
 static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx)
 {
 	u32 exit_intr_info;
@@ -11239,6 +11244,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
 	.handle_external_intr = vmx_handle_external_intr,
 	.mpx_supported = vmx_mpx_supported,
 	.xsaves_supported = vmx_xsaves_supported,
+	.umip_emulated = vmx_umip_emulated,
 
 	.check_nested_events = vmx_check_nested_events,
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 548f546f92db..85c7e8135342 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -746,6 +746,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 	if (!guest_cpuid_has_pku(vcpu) && (cr4 & X86_CR4_PKE))
 		return 1;
 
+	if (!guest_cpuid_has_umip(vcpu) && (cr4 & X86_CR4_UMIP))
+		return 1;
+
 	if (is_long_mode(vcpu)) {
 		if (!(cr4 & X86_CR4_PAE))
 			return 1;
-- 
1.8.3.1

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#1442803

2016-07-12 21:20+0200, Paolo Bonzini:
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> @@ -3738,6 +3747,10 @@ static int em_lidt(struct x86_emulate_ctxt *ctxt)
>  
>  static int em_smsw(struct x86_emulate_ctxt *ctxt)
>  {
> +	if ((ctxt->ops->get_cr(ctxt, 4) & X86_CR4_UMIP) &&
> +	    ctxt->ops->cpl(ctxt) > 0)

UMIP should #GP(0) in virtual-8086 mode too (for SMSW, SIDT, and SGDT),
but cpl() returns 0 in vm86.

> +		return emulate_gp(ctxt, 0);

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#1443124

On 13/07/2016 22:03, Radim Krčmář wrote:
> 2016-07-12 21:20+0200, Paolo Bonzini:
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>> @@ -3738,6 +3747,10 @@ static int em_lidt(struct x86_emulate_ctxt *ctxt)
>>  
>>  static int em_smsw(struct x86_emulate_ctxt *ctxt)
>>  {
>> +	if ((ctxt->ops->get_cr(ctxt, 4) & X86_CR4_UMIP) &&
>> +	    ctxt->ops->cpl(ctxt) > 0)
> 
> UMIP should #GP(0) in virtual-8086 mode too (for SMSW, SIDT, and SGDT),
> but cpl() returns 0 in vm86.

No, it returns 3.

vmx->rmode.vm86_active means "there is no unrestricted guest support,
and we're using VM86 mode to emulate real mode".  The special case in
vmx_get_cpl is needed exactly because real mode CPL is 0 but VM86 has
CPL 3.  In fact fix_rmode_seg sets DPL=3 for all segments, and CPL=SS.DPL.

Paolo

>> +		return emulate_gp(ctxt, 0);
> --
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> 

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#1443405

2016-07-14 09:00+0200, Paolo Bonzini:
> On 13/07/2016 22:03, Radim Krčmář wrote:
>> 2016-07-12 21:20+0200, Paolo Bonzini:
>>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>> ---
>>> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>>> @@ -3738,6 +3747,10 @@ static int em_lidt(struct x86_emulate_ctxt *ctxt)
>>>  
>>>  static int em_smsw(struct x86_emulate_ctxt *ctxt)
>>>  {
>>> +	if ((ctxt->ops->get_cr(ctxt, 4) & X86_CR4_UMIP) &&
>>> +	    ctxt->ops->cpl(ctxt) > 0)
>> 
>> UMIP should #GP(0) in virtual-8086 mode too (for SMSW, SIDT, and SGDT),
>> but cpl() returns 0 in vm86.
> 
> No, it returns 3.
> 
> vmx->rmode.vm86_active means "there is no unrestricted guest support,
> and we're using VM86 mode to emulate real mode".  The special case in
> vmx_get_cpl is needed exactly because real mode CPL is 0 but VM86 has
> CPL 3.  In fact fix_rmode_seg sets DPL=3 for all segments, and CPL=SS.DPL.

Right, thanks.

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