Re: [RFC][PATCH] Add support for the GUEST_SMBASE VMCS field for Intel VT-x.

[Avi Kivity <avi@redhat.com>]

On 06/05/2012 02:59 PM, Matthias Lange wrote:
> On Sun, May 20, 2012 at 03:39:30PM +0300, Avi Kivity wrote:
>> On 05/18/2012 12:34 PM, Matthias Lange wrote:
>> > The following patch adds support for the GUEST_SMBASE field. This allows
>> > hypervisors running inside kvm read/write access to this field. I have
>> > tested this to work on a Core i5 machine.
>> >
>> > diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
>> > index 31f180c..6a14720 100644
>> > --- a/arch/x86/include/asm/vmx.h
>> > +++ b/arch/x86/include/asm/vmx.h
>> > @@ -194,6 +194,7 @@ enum vmcs_field {
>> >  	GUEST_TR_AR_BYTES               = 0x00004822,
>> >  	GUEST_INTERRUPTIBILITY_INFO     = 0x00004824,
>> >  	GUEST_ACTIVITY_STATE            = 0X00004826,
>> > +	GUEST_SMBASE			= 0x00004828,
>> >  	GUEST_SYSENTER_CS               = 0x0000482A,
>> >  	HOST_IA32_SYSENTER_CS           = 0x00004c00,
>> >  	CR0_GUEST_HOST_MASK             = 0x00006000,
>> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> > index 4ff0ab9..0063743 100644
>> > --- a/arch/x86/kvm/vmx.c
>> > +++ b/arch/x86/kvm/vmx.c
>> > @@ -285,6 +285,7 @@ struct __packed vmcs12 {
>> >  	u32 guest_tr_ar_bytes;
>> >  	u32 guest_interruptibility_info;
>> >  	u32 guest_activity_state;
>> > +	u32 guest_smbase;
>> >  	u32 guest_sysenter_cs;
>> >  	u32 host_ia32_sysenter_cs;
>> >  	u32 padding32[8]; /* room for future expansion */
>> > @@ -546,6 +547,7 @@ static unsigned short vmcs_field_to_offset_table[] = {
>> >
>> 
>> vmcs12 is an ABI, so you can't insert fields at random.  Grab one from
>> padding32.
> 
> Do you mean the ABI defined in the Intel Software Developer's manual 3B? Or is
> vmcs12 only an ABI internal to the kvm module?

The latter.  We want to be able to live migrate a guest with nested
guests, and if the format of vmcs12 changes, the migration will break.

> 
> I understand that my patch is wrong because I need to decrease the size of
> padding32. I tested the patch by running Ubuntu 12.04 as the L1 guest and
> Tinycore Linux as the L2 guest.
> 
> Let me know what you think.
> 



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error compiling committee.c: too many arguments to function