Re: [Xen-devel] [PATCH 07/10] VMX: handle PML enabling in vmx_vcpu_initialise

[Kai Huang <kai.huang@xxxxxxxxxxxxxxx>]

On 03/28/2015 05:12 AM, Andrew Cooper wrote:
> On 27/03/15 02:35, Kai Huang wrote:
> > It's possible domain has already been in log-dirty mode when creating vcpu, in
> > which case we should enable PML for this vcpu if PML has been enabled for the
> > domain.
> >
> > Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
> > ---
> >   xen/arch/x86/hvm/vmx/vmx.c | 24 ++++++++++++++++++++++++
> >   1 file changed, 24 insertions(+)
> >
> > diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> > index 453bcc5..fce3aa2 100644
> > --- a/xen/arch/x86/hvm/vmx/vmx.c
> > +++ b/xen/arch/x86/hvm/vmx/vmx.c
> > @@ -116,6 +116,30 @@ static int vmx_vcpu_initialise(struct vcpu *v)
> >           return rc;
> >       }
> >   
> > +    /*
> > +     * It's rare but still possible that domain has already been in log-dirty
> > +     * mode when vcpu is being created (commented by Tim), in which case we
> > +     * should enable PML for this vcpu if PML has been enabled for the domain,
> > +     * and failure to enable results in failure of creating this vcpu.
> > +     *
> > +     * Note even there's no vcpu created for the domain, vmx_domain_enable_pml
> > +     * will return successful in which case vmx_domain_pml_enabled will also
> > +     * return true. And even this is the first vcpu to be created with
> > +     * vmx_domain_pml_enabled being true, failure of enabling PML still results
> > +     * in failure of creating vcpu, to avoid complicated logic to revert PML
> > +     * style EPT table to non-PML style EPT table.
> > +     */
> > +    if ( vmx_domain_pml_enabled(v->domain) )
> > +    {
> > +        if ( (rc = vmx_vcpu_enable_pml(v)) != 0 )
> Given the comment here, is the assertion in the top of
> vmx_vcpu_enable_pml() liable to trip?
Do you mean below assertion at beginning of vmx_vcpu_enable_pml might 
not work here?
    ASSERT(!vmx_vcpu_pml_enabled(v));

To me it asserts for this particular vcpu, not the domain, so even in 
this case the assertion is reasonable and should work fine, shouldn't it?
> > +        {
> > +            dprintk(XENLOG_ERR, "Failed to enable PML for vcpu %d\n",
> > +                    v->vcpu_id);
> Please use %pv to identify the domain as well as vcpu.
Sure.

Thanks,
-Kai
> ~Andrew
>
> > +            vmx_destroy_vmcs(v);
> > +            return rc;
> > +        }
> > +    }
> > +
> >       vpmu_initialise(v);
> >   
> >       vmx_install_vlapic_mapping(v);
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