Re: [Xen-devel] [PATCH v2 11/16] x86: don't set sysenter_entry in vmcs when !CONFIG_PV

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Oct 19, 2018 at 04:42:24PM +0100, Andrew Cooper wrote:
> On 19/10/18 15:28, Wei Liu wrote:
> > The symbol will not be available when PV is disabled.
> >
> > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > ---
> > v2: new
> > ---
> >  xen/arch/x86/hvm/vmx/vmcs.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
> > index d9747b4..282677a 100644
> > --- a/xen/arch/x86/hvm/vmx/vmcs.c
> > +++ b/xen/arch/x86/hvm/vmx/vmcs.c
> > @@ -1159,9 +1159,16 @@ static int construct_vmcs(struct vcpu *v)
> >      __vmwrite(HOST_CS_SELECTOR, __HYPERVISOR_CS);
> >      __vmwrite(HOST_RIP, (unsigned long)vmx_asm_vmexit_handler);
> >  
> > +#ifdef CONFIG_PV
> >      /* Host SYSENTER CS:RIP. */
> >      __vmwrite(HOST_SYSENTER_CS, __HYPERVISOR_CS);
> >      __vmwrite(HOST_SYSENTER_EIP, (unsigned long)sysenter_entry);
> > +#else
> > +    /*
> > +     * Should something be put here for debugging purpose? We never
> > +     * set it up in the first place.
> 
> With MSR_SYSENTER_CS set to 0, SYSENTER/SYSEXIT instructions
> automatically #GP[0].

OK. So we should initialise MSR_SYSENTER_CS to 0 in a previous patch.

Wei.

> 
> I don't think we need anything here in the !PV case.
> 
> ~Andrew

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