* [PATCH] Add GDT, IDT and RFLAGS guest state validity checks
@ 2009-09-21 15:33 Mohammed Gamal
2009-09-22 7:13 ` Avi Kivity
0 siblings, 1 reply; 3+ messages in thread
From: Mohammed Gamal @ 2009-09-21 15:33 UTC (permalink / raw)
To: avi; +Cc: mtosatti, kvm, Mohammed Gamal
With emulate_invalid_guest_state=1 Windows XP exits with an invalid guest state
due to rflags not being in a VMX-compliant state. This patch fixes this issue,
although Windows XP doesn't boot yet with invalid state emulation on.
Also added GDT and IDT checks while we're at it.
Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
---
arch/x86/kvm/vmx.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 56 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 3fe0d42..eaec4a5 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2022,6 +2022,23 @@ static bool ldtr_valid(struct kvm_vcpu *vcpu)
return true;
}
+static bool gdtr_idtr_valid(struct kvm_vcpu *vcpu)
+{
+ struct descriptor_table gdt;
+ struct descriptor_table idt;
+
+ vmx_get_gdt(vcpu, &gdt);
+ vmx_get_idt(vcpu, &idt);
+
+ if (gdt.limit & 0xffff0000)
+ return false;
+
+ if (idt.limit & 0xffff0000)
+ return false;
+
+ return true;
+}
+
static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
{
struct kvm_segment cs, ss;
@@ -2033,6 +2050,41 @@ static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
(ss.selector & SELECTOR_RPL_MASK));
}
+static bool rflags_valid(struct kvm_vcpu *vcpu)
+{
+ unsigned long rflags;
+ u32 entry_intr_info;
+
+ rflags = vmcs_readl(GUEST_RFLAGS);
+ entry_intr_info = vmcs_read32(VM_ENTRY_INTR_INFO_FIELD);
+#ifdef CONFIG_X86_64
+ if (rflags & 0xffffffffffc00000)
+ return false;
+ if (is_long_mode(vcpu))
+ if (rflags & X86_EFLAGS_VM)
+ return false;
+#else
+ if (rflags & 0xffc00000)
+ return false;
+#endif
+ if (rflags & 0x8000)
+ return false;
+ if (rflags & 0x20)
+ return false;
+ if (rflags & 0x8)
+ return false;
+ if (!(rflags & 0x2))
+ return false;
+
+ if ((entry_intr_info & INTR_INFO_INTR_TYPE_MASK) == INTR_TYPE_EXT_INTR
+ && (entry_intr_info & INTR_INFO_VALID_MASK)) {
+ if (!(rflags & X86_EFLAGS_IF))
+ return false;
+ }
+
+ return true;
+}
+
/*
* Check if guest state is valid. Returns true if valid, false if
* not.
@@ -2077,8 +2129,11 @@ static bool guest_state_valid(struct kvm_vcpu *vcpu)
}
/* TODO:
* - Add checks on RIP
- * - Add checks on RFLAGS
*/
+ if (!rflags_valid(vcpu))
+ return false;
+ if (!gdtr_idtr_valid(vcpu))
+ return false;
return true;
}
--
1.6.0.4
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] Add GDT, IDT and RFLAGS guest state validity checks
2009-09-21 15:33 [PATCH] Add GDT, IDT and RFLAGS guest state validity checks Mohammed Gamal
@ 2009-09-22 7:13 ` Avi Kivity
2009-09-22 7:21 ` Mohammed Gamal
0 siblings, 1 reply; 3+ messages in thread
From: Avi Kivity @ 2009-09-22 7:13 UTC (permalink / raw)
To: Mohammed Gamal; +Cc: mtosatti, kvm
On 09/21/2009 06:33 PM, Mohammed Gamal wrote:
> With emulate_invalid_guest_state=1 Windows XP exits with an invalid guest state
> due to rflags not being in a VMX-compliant state. This patch fixes this issue,
> although Windows XP doesn't boot yet with invalid state emulation on.
>
> Also added GDT and IDT checks while we're at it.
>
> Signed-off-by: Mohammed Gamal<m.gamal005@gmail.com>
> ---
> arch/x86/kvm/vmx.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 files changed, 56 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 3fe0d42..eaec4a5 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2022,6 +2022,23 @@ static bool ldtr_valid(struct kvm_vcpu *vcpu)
> return true;
> }
>
> +static bool gdtr_idtr_valid(struct kvm_vcpu *vcpu)
> +{
> + struct descriptor_table gdt;
> + struct descriptor_table idt;
> +
> + vmx_get_gdt(vcpu,&gdt);
> + vmx_get_idt(vcpu,&idt);
> +
> + if (gdt.limit& 0xffff0000)
> + return false;
> +
> + if (idt.limit& 0xffff0000)
> + return false;
> +
> + return true;
> +}
>
gdt and idt limits cannot be > 0xffff, since the intstructions to load
them always use a 16 bit quantity.
> +
> static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
> {
> struct kvm_segment cs, ss;
> @@ -2033,6 +2050,41 @@ static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
> (ss.selector& SELECTOR_RPL_MASK));
> }
>
> +static bool rflags_valid(struct kvm_vcpu *vcpu)
> +{
> + unsigned long rflags;
> + u32 entry_intr_info;
> +
> + rflags = vmcs_readl(GUEST_RFLAGS);
> + entry_intr_info = vmcs_read32(VM_ENTRY_INTR_INFO_FIELD);
> +#ifdef CONFIG_X86_64
> + if (rflags& 0xffffffffffc00000)
> + return false;
> + if (is_long_mode(vcpu))
> + if (rflags& X86_EFLAGS_VM)
> + return false;
> +#else
> + if (rflags& 0xffc00000)
> + return false;
> +#endif
> + if (rflags& 0x8000)
> + return false;
> + if (rflags& 0x20)
> + return false;
> + if (rflags& 0x8)
> + return false;
> + if (!(rflags& 0x2))
> + return false;
> +
> + if ((entry_intr_info& INTR_INFO_INTR_TYPE_MASK) == INTR_TYPE_EXT_INTR
> + && (entry_intr_info& INTR_INFO_VALID_MASK)) {
> + if (!(rflags& X86_EFLAGS_IF))
> + return false;
> + }
> +
> + return true;
> +}
>
It's really difficult to tell what you are doing here since you're using
numbers instead of symbolic constants. But I think some of these are
generally illegal. !guest_state_valid() means "the state is valid for
x86 but not valid for vmx entry"; if it's generally invalid all bets are
off.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] Add GDT, IDT and RFLAGS guest state validity checks
2009-09-22 7:13 ` Avi Kivity
@ 2009-09-22 7:21 ` Mohammed Gamal
0 siblings, 0 replies; 3+ messages in thread
From: Mohammed Gamal @ 2009-09-22 7:21 UTC (permalink / raw)
To: Avi Kivity; +Cc: mtosatti, kvm
On Tue, Sep 22, 2009 at 9:13 AM, Avi Kivity <avi@redhat.com> wrote:
> On 09/21/2009 06:33 PM, Mohammed Gamal wrote:
>>
>> With emulate_invalid_guest_state=1 Windows XP exits with an invalid guest
>> state
>> due to rflags not being in a VMX-compliant state. This patch fixes this
>> issue,
>> although Windows XP doesn't boot yet with invalid state emulation on.
>>
>> Also added GDT and IDT checks while we're at it.
>>
>> Signed-off-by: Mohammed Gamal<m.gamal005@gmail.com>
>> ---
>> arch/x86/kvm/vmx.c | 57
>> +++++++++++++++++++++++++++++++++++++++++++++++++++-
>> 1 files changed, 56 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 3fe0d42..eaec4a5 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -2022,6 +2022,23 @@ static bool ldtr_valid(struct kvm_vcpu *vcpu)
>> return true;
>> }
>>
>> +static bool gdtr_idtr_valid(struct kvm_vcpu *vcpu)
>> +{
>> + struct descriptor_table gdt;
>> + struct descriptor_table idt;
>> +
>> + vmx_get_gdt(vcpu,&gdt);
>> + vmx_get_idt(vcpu,&idt);
>> +
>> + if (gdt.limit& 0xffff0000)
>> + return false;
>> +
>> + if (idt.limit& 0xffff0000)
>> + return false;
>> +
>> + return true;
>> +}
>>
>
> gdt and idt limits cannot be > 0xffff, since the intstructions to load them
> always use a 16 bit quantity.
>
>> +
>> static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
>> {
>> struct kvm_segment cs, ss;
>> @@ -2033,6 +2050,41 @@ static bool cs_ss_rpl_check(struct kvm_vcpu *vcpu)
>> (ss.selector& SELECTOR_RPL_MASK));
>> }
>>
>> +static bool rflags_valid(struct kvm_vcpu *vcpu)
>> +{
>> + unsigned long rflags;
>> + u32 entry_intr_info;
>> +
>> + rflags = vmcs_readl(GUEST_RFLAGS);
>> + entry_intr_info = vmcs_read32(VM_ENTRY_INTR_INFO_FIELD);
>> +#ifdef CONFIG_X86_64
>> + if (rflags& 0xffffffffffc00000)
>> + return false;
>> + if (is_long_mode(vcpu))
>> + if (rflags& X86_EFLAGS_VM)
>> + return false;
>> +#else
>> + if (rflags& 0xffc00000)
>> + return false;
>> +#endif
>> + if (rflags& 0x8000)
>> + return false;
>> + if (rflags& 0x20)
>> + return false;
>> + if (rflags& 0x8)
>> + return false;
>> + if (!(rflags& 0x2))
>> + return false;
>> +
>> + if ((entry_intr_info& INTR_INFO_INTR_TYPE_MASK) ==
>> INTR_TYPE_EXT_INTR
>> + && (entry_intr_info& INTR_INFO_VALID_MASK)) {
>> + if (!(rflags& X86_EFLAGS_IF))
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>>
>
> It's really difficult to tell what you are doing here since you're using
> numbers instead of symbolic constants. But I think some of these are
> generally illegal. !guest_state_valid() means "the state is valid for x86
> but not valid for vmx entry"; if it's generally invalid all bets are off.
>
The checks are based on those mentioned in the Intel Software
Developer Manual Vol. 2 Section 22.3.1.3 and 22.3.1.4
^ permalink raw reply [flat|nested] 3+ messages in thread
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2009-09-21 15:33 [PATCH] Add GDT, IDT and RFLAGS guest state validity checks Mohammed Gamal
2009-09-22 7:13 ` Avi Kivity
2009-09-22 7:21 ` Mohammed Gamal
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