[PATCH 1/2] VMX: Properly return error to userspace on vmentry failure

[PATCH 1/2] VMX: Properly return error to userspace on vmentry failure

[Mohammed Gamal]

The vmexit handler returns KVM_EXIT_UNKNOWN since there is no handler
for vmentry failures. This intercepts vmentry failures and returns
KVM_FAIL_ENTRY to userspace instead.

Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
---
 arch/x86/kvm/vmx.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 99ae513..4edcffb 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3665,6 +3665,13 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
 	if (enable_ept && is_paging(vcpu))
 		vcpu->arch.cr3 = vmcs_readl(GUEST_CR3);
 
+	if (exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) {
+		vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
+		vcpu->run->fail_entry.hardware_entry_failure_reason
+			= exit_reason & ~VMX_EXIT_REASONS_FAILED_VMENTRY;
+		return 0;
+	}
+
 	if (unlikely(vmx->fail)) {
 		vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
 		vcpu->run->fail_entry.hardware_entry_failure_reason
-- 
1.7.0.4

[PATCH 2/2] VMX: Add constant for invalid guest state exit reason

[Mohammed Gamal]

For the sake of completeness, this patch adds a symbolic
constant for VMX exit reason 0x21 (invalid guest state).

Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
---
 arch/x86/include/asm/vmx.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 9e6779f..104cf86 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -257,6 +257,7 @@ enum vmcs_field {
 #define EXIT_REASON_IO_INSTRUCTION      30
 #define EXIT_REASON_MSR_READ            31
 #define EXIT_REASON_MSR_WRITE           32
+#define EXIT_REASON_INVALID_STATE	33
 #define EXIT_REASON_MWAIT_INSTRUCTION   36
 #define EXIT_REASON_MONITOR_INSTRUCTION 39
 #define EXIT_REASON_PAUSE_INSTRUCTION   40
-- 
1.7.0.4

Re: [PATCH 1/2] VMX: Properly return error to userspace on vmentry failure

[Avi Kivity]

On 05/24/2010 01:01 AM, Mohammed Gamal wrote:
> The vmexit handler returns KVM_EXIT_UNKNOWN since there is no handler
> for vmentry failures. This intercepts vmentry failures and returns
> KVM_FAIL_ENTRY to userspace instead.
>
> Signed-off-by: Mohammed Gamal<m.gamal005@gmail.com>
> ---
>   arch/x86/kvm/vmx.c |    7 +++++++
>   1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 99ae513..4edcffb 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3665,6 +3665,13 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
>   	if (enable_ept&&  is_paging(vcpu))
>   		vcpu->arch.cr3 = vmcs_readl(GUEST_CR3);
>
> +	if (exit_reason&  VMX_EXIT_REASONS_FAILED_VMENTRY) {
> +		vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
> +		vcpu->run->fail_entry.hardware_entry_failure_reason
> +			= exit_reason&  ~VMX_EXIT_REASONS_FAILED_VMENTRY;
> +		return 0;
> +	}
> +
>   	if (unlikely(vmx->fail)) {
>   		vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
>   		vcpu->run->fail_entry.hardware_entry_failure_reason
>    

How does the user distinguish between KVM_EXIT_FAIL_ENTRY due to an exit 
reason with bit 31 set and vmlauch/vmresume failure (vmx->fail set)?  We 
need separate exit codes (with documentation in api.txt).

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

Re: [PATCH 2/2] VMX: Add constant for invalid guest state exit reason

[Avi Kivity]

On 05/24/2010 01:01 AM, Mohammed Gamal wrote:
> For the sake of completeness, this patch adds a symbolic
> constant for VMX exit reason 0x21 (invalid guest state).
>    

Applied, thanks.

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

Re: [PATCH 1/2] VMX: Properly return error to userspace on vmentry failure

[Mohammed Gamal]

On Tue, May 25, 2010 at 2:45 PM, Avi Kivity <avi@redhat.com> wrote:
> On 05/24/2010 01:01 AM, Mohammed Gamal wrote:
>>
>> The vmexit handler returns KVM_EXIT_UNKNOWN since there is no handler
>> for vmentry failures. This intercepts vmentry failures and returns
>> KVM_FAIL_ENTRY to userspace instead.
>>
>> Signed-off-by: Mohammed Gamal<m.gamal005@gmail.com>
>> ---
>>  arch/x86/kvm/vmx.c |    7 +++++++
>>  1 files changed, 7 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 99ae513..4edcffb 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -3665,6 +3665,13 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
>>        if (enable_ept&&  is_paging(vcpu))
>>                vcpu->arch.cr3 = vmcs_readl(GUEST_CR3);
>>
>> +       if (exit_reason&  VMX_EXIT_REASONS_FAILED_VMENTRY) {
>> +               vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
>> +               vcpu->run->fail_entry.hardware_entry_failure_reason
>> +                       = exit_reason&  ~VMX_EXIT_REASONS_FAILED_VMENTRY;
>> +               return 0;
>> +       }
>> +
>>        if (unlikely(vmx->fail)) {
>>                vcpu->run->exit_reason = KVM_EXIT_FAIL_ENTRY;
>>                vcpu->run->fail_entry.hardware_entry_failure_reason
>>
>
> How does the user distinguish between KVM_EXIT_FAIL_ENTRY due to an exit
> reason with bit 31 set and vmlauch/vmresume failure (vmx->fail set)?  We
> need separate exit codes (with documentation in api.txt).

In both cases the vm fails entry, and I don't think the hardware entry
failure reason codes would overlap between the vmx->fail case and exit
reasons with bit 31 set, so why should there be such distinction
between both cases?
>
> --
> error compiling committee.c: too many arguments to function
>
>

Re: [PATCH 1/2] VMX: Properly return error to userspace on vmentry failure

[Avi Kivity]

On 05/25/2010 03:01 PM, Mohammed Gamal wrote:
>>
>> How does the user distinguish between KVM_EXIT_FAIL_ENTRY due to an exit
>> reason with bit 31 set and vmlauch/vmresume failure (vmx->fail set)?  We
>> need separate exit codes (with documentation in api.txt).
>>      
> In both cases the vm fails entry, and I don't think the hardware entry
> failure reason codes would overlap between the vmx->fail case and exit
> reasons with bit 31 set, so why should there be such distinction
> between both cases?
>    

Only 5 more error codes (28->33) and we have overlap.

If you return the new codes with bit 31 still set then we can use the 
existing KVM_EXIT_FAIL_ENTRY.


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

Re: [PATCH 1/2] VMX: Properly return error to userspace on vmentry failure

[Mohammed Gamal]

On Tue, May 25, 2010 at 3:10 PM, Avi Kivity <avi@redhat.com> wrote:
> On 05/25/2010 03:01 PM, Mohammed Gamal wrote:
>>>
>>> How does the user distinguish between KVM_EXIT_FAIL_ENTRY due to an exit
>>> reason with bit 31 set and vmlauch/vmresume failure (vmx->fail set)?  We
>>> need separate exit codes (with documentation in api.txt).
>>>
>>
>> In both cases the vm fails entry, and I don't think the hardware entry
>> failure reason codes would overlap between the vmx->fail case and exit
>> reasons with bit 31 set, so why should there be such distinction
>> between both cases?
>>
>
> Only 5 more error codes (28->33) and we have overlap.
>
> If you return the new codes with bit 31 still set then we can use the
> existing KVM_EXIT_FAIL_ENTRY.

That'd be a better idea.

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