Re: [Xen-devel] [PATCH v11 05/12] xen/pvh: Update E820 to work with PVH

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 17 Dec 2013, Konrad Rzeszutek Wilk wrote:
> From: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
> 
> In xen_add_extra_mem() we can skip updating P2M as it's managed
> by Xen. PVH maps the entire IO space, but only RAM pages need
> to be repopulated.
> 
> Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
>  arch/x86/xen/setup.c | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index 2137c51..f93bca1 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -27,6 +27,7 @@
>  #include <xen/interface/memory.h>
>  #include <xen/interface/physdev.h>
>  #include <xen/features.h>
> +#include "mmu.h"
>  #include "xen-ops.h"
>  #include "vdso.h"
>  
> @@ -81,6 +82,9 @@ static void __init xen_add_extra_mem(u64 start, u64 size)
>  
>       memblock_reserve(start, size);
>  
> +     if (xen_feature(XENFEAT_auto_translated_physmap))
> +             return;
> +
>       xen_max_p2m_pfn = PFN_DOWN(start + size);
>       for (pfn = PFN_DOWN(start); pfn < xen_max_p2m_pfn; pfn++) {
>               unsigned long mfn = pfn_to_mfn(pfn);
> @@ -103,6 +107,7 @@ static unsigned long __init xen_do_chunk(unsigned long 
> start,
>               .domid        = DOMID_SELF
>       };
>       unsigned long len = 0;
> +     int xlated_phys = xen_feature(XENFEAT_auto_translated_physmap);
>       unsigned long pfn;
>       int ret;
>  
> @@ -116,7 +121,7 @@ static unsigned long __init xen_do_chunk(unsigned long 
> start,
>                               continue;
>                       frame = mfn;
>               } else {
> -                     if (mfn != INVALID_P2M_ENTRY)
> +                     if (!xlated_phys && mfn != INVALID_P2M_ENTRY)
>                               continue;
>                       frame = pfn;
>               }
> @@ -154,6 +159,13 @@ static unsigned long __init xen_do_chunk(unsigned long 
> start,
>  static unsigned long __init xen_release_chunk(unsigned long start,
>                                             unsigned long end)
>  {
> +     /*
> +      * Xen already ballooned out the E820 non RAM regions for us
> +      * and set them up properly in EPT.
> +      */
> +     if (xen_feature(XENFEAT_auto_translated_physmap))
> +             return end - start;
> +
>       return xen_do_chunk(start, end, true);
>  }
>  
> @@ -222,6 +234,9 @@ static void __init xen_set_identity_and_release_chunk(
>        * (except for the ISA region which must be 1:1 mapped) to
>        * release the refcounts (in Xen) on the original frames.
>        */
> +     if (xen_feature(XENFEAT_auto_translated_physmap))
> +             goto skip;
> +
>       for (pfn = start_pfn; pfn <= max_pfn_mapped && pfn < end_pfn; pfn++) {
>               pte_t pte = __pte_ma(0);
>  
> @@ -231,7 +246,7 @@ static void __init xen_set_identity_and_release_chunk(
>               (void)HYPERVISOR_update_va_mapping(
>                       (unsigned long)__va(pfn << PAGE_SHIFT), pte, 0);
>       }
> -
> +skip:
>       if (start_pfn < nr_pages)
>               *released += xen_release_chunk(
>                       start_pfn, min(end_pfn, nr_pages));

A goto? Really? What's wrong with an if?
Also considering that you are turning xen_release_chunk into a nop, the
only purpose of this function on PVH is to call set_phys_range_identity.
Can't we just do that?

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