Re: [v3 01/10] vmx: add new boot parameter to control PML enabling

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 24/04/15 09:19, Kai Huang wrote:
> A top level EPT parameter "ept=<options>" and a sub boolean "opt_pml_enabled"
> are added to control PML. Other booleans can be further added for any other EPT
> related features.
>
> The document description for the new parameter is also added.
>
> Signed-off-by: Kai Huang <kai.huang@linux.intel.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

> ---
>  docs/misc/xen-command-line.markdown | 15 +++++++++++++++
>  xen/arch/x86/hvm/vmx/vmcs.c         | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 45 insertions(+)
>
> diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
> index 1dda1f0..4889e27 100644
> --- a/docs/misc/xen-command-line.markdown
> +++ b/docs/misc/xen-command-line.markdown
> @@ -685,6 +685,21 @@ requirement can be relaxed.  This option is particularly useful for nested
>  virtualization, to allow the L1 hypervisor to use EPT even if the L0 hypervisor
>  does not provide VM\_ENTRY\_LOAD\_GUEST\_PAT.
>  
> +### ept (Intel)
> +> `= List of ( pml<boolean> )`
> +
> +> Default: `false`
> +
> +Controls EPT related features. Currently only Page Modification Logging (PML) is
> +the controllable feature as boolean type.
> +
> +PML is a new hardware feature in Intel's Broadwell Server and further platforms
> +which reduces hypervisor overhead of log-dirty mechanism by automatically
> +recording GPAs (guest physical addresses) when guest memory gets dirty, and
> +therefore significantly reducing number of EPT violation caused by write
> +protection of guest memory, which is a necessity to implement log-dirty
> +mechanism before PML.
> +
>  ### gdb
>  > `= <baud>[/<clock_hz>][,DPS[,<io-base>[,<irq>[,<port-bdf>[,<bridge-bdf>]]]] | pci | amt ] `
>  
> diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
> index 63007a9..79efa42 100644
> --- a/xen/arch/x86/hvm/vmx/vmcs.c
> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
> @@ -64,6 +64,36 @@ integer_param("ple_gap", ple_gap);
>  static unsigned int __read_mostly ple_window = 4096;
>  integer_param("ple_window", ple_window);
>  
> +static bool_t __read_mostly opt_pml_enabled = 0;
> +
> +/*
> + * The 'ept' parameter controls functionalities that depend on, or impact the
> + * EPT mechanism. Optional comma separated value may contain:
> + *
> + *  pml                 Enable PML
> + */
> +static void __init parse_ept_param(char *s)
> +{
> +    char *ss;
> +
> +    do {
> +        bool_t val = !!strncmp(s, "no-", 3);
> +        if ( !val )
> +            s += 3;
> +
> +        ss = strchr(s, ',');
> +        if ( ss )
> +            *ss = '\0';
> +
> +        if ( !strcmp(s, "pml") )
> +            opt_pml_enabled = val;
> +
> +        s = ss + 1;
> +    } while ( ss );
> +}
> +
> +custom_param("ept", parse_ept_param);
> +
>  /* Dynamic (run-time adjusted) execution control flags. */
>  u32 vmx_pin_based_exec_control __read_mostly;
>  u32 vmx_cpu_based_exec_control __read_mostly;