Re: [Xen-devel] [PATCH] x86/EPT: defer enabling of A/D maintenance until PML get enabled

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.10.15 at 08:42, <kai.huang@xxxxxxxxxxxxxxx> wrote:
> Thanks for your comments Jan. Actually I am not happy with combining 
> with EPT A/D bit update with PML enabling to single function. After 
> thinking again, how about adding a separate vmx function (ex, 
> vmx_domain_update_eptp) to update EPTP of VMCS of all vcpus of domain 
> after p2m->ept.ept_ad is updated. Another good is this function can also 
> be used in the future for other runtime updates to p2m->ept.
> 
> What's your idea?

I don't mind, but that's really more of a question to the VMX maintainers.

> --- a/xen/arch/x86/mm/p2m-ept.c
> +++ b/xen/arch/x86/mm/p2m-ept.c
> @@ -1129,17 +1129,26 @@ void ept_sync_domain(struct p2m_domain *p2m)
> 
>   static void ept_enable_pml(struct p2m_domain *p2m)
>   {
>       /*
> -     * No need to check if vmx_domain_enable_pml has succeeded or not, as
> +     * No need to return if vmx_domain_enable_pml has succeeded or not, as

It seems to me that you'd better use "whether" instead of "if" now
(and then perhaps also drop the "or not").

>        * ept_p2m_type_to_flags will do the check, and write protection will be
>        * used if PML is not enabled.
>        */
> -    vmx_domain_enable_pml(p2m->domain);
> +    if ( vmx_domain_enable_pml(p2m->domain) )
> +        return;
> +
> +    p2m->ept.ept_ad = 1;
> +    vmx_domain_update_eptp(p2m->domain);

Shouldn't you enable A/D _before_ enabling PML, at least without
having a domain-is-paused check here?

Jan


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