Re: [Xen-devel] [PATCH V3 1/6]: PVH: basic and header changes, elfnote changes, ...

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 18 Oct 2012, Mukesh Rathor wrote:
> [PATCH 1/6] PVH: is a PV linux guest that has extended capabilities. This 
> patch allows it to be configured and enabled. Also, basic header file changes 
> to add new subcalls to physmap hypercall. Lastly, mfn_to_local_pfn must 
> return mfn for paging mode translate.
> 
> Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
> ---
>  arch/x86/include/asm/xen/page.h |    3 +++
>  arch/x86/xen/Kconfig            |   10 ++++++++++
>  arch/x86/xen/xen-head.S         |   11 ++++++++++-
>  include/xen/interface/memory.h  |   24 +++++++++++++++++++++++-
>  include/xen/interface/physdev.h |   10 ++++++++++
>  5 files changed, 56 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
> index 472b9b7..6af440d 100644
> --- a/arch/x86/include/asm/xen/page.h
> +++ b/arch/x86/include/asm/xen/page.h
> @@ -159,6 +159,9 @@ static inline xpaddr_t machine_to_phys(xmaddr_t machine)
>  static inline unsigned long mfn_to_local_pfn(unsigned long mfn)
>  {
>       unsigned long pfn = mfn_to_pfn(mfn);
> +
> +     if (xen_feature(XENFEAT_auto_translated_physmap))
> +             return mfn;
>       if (get_phys_to_machine(pfn) != mfn)
>               return -1; /* force !pfn_valid() */
>       return pfn;
> diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
> index fdce49c..822c5a0 100644
> --- a/arch/x86/xen/Kconfig
> +++ b/arch/x86/xen/Kconfig
> @@ -50,3 +50,13 @@ config XEN_DEBUG_FS
>         Enable statistics output and various tuning options in debugfs.
>         Enabling this option may incur a significant performance overhead.
>  
> +config XEN_X86_PVH
> +     bool "Support for running as a PVH guest (EXPERIMENTAL)"
> +     depends on X86_64 && XEN && EXPERIMENTAL
> +     default n
> +     help
> +        This option enables support for running as a PVH guest (PV guest
> +        using hardware extensions) under a suitably capable hypervisor.
> +        This option is EXPERIMENTAL because the hypervisor interfaces
> +        which it uses are not yet considered stable therefore backwards and
> +        forwards compatibility is not yet guaranteed.  If unsure, say N.

Do we really need the kconfig symbol? Why can't we have it always
enabled?


> diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
> index 7faed58..1a6bca1 100644
> --- a/arch/x86/xen/xen-head.S
> +++ b/arch/x86/xen/xen-head.S
> @@ -13,6 +13,15 @@
>  #include <xen/interface/elfnote.h>
>  #include <asm/xen/interface.h>
>  
> +#ifdef CONFIG_XEN_X86_PVH
> +#define FEATURES_PVH "|writable_descriptor_tables" \
> +                  "|auto_translated_physmap" \
> +                  "|supervisor_mode_kernel" \
> +                  "|hvm_callback_vector"
> +#else
> +#define FEATURES_PVH /* Not supported */
> +#endif
> +
>       __INIT
>  ENTRY(startup_xen)
>       cld
> @@ -95,7 +104,7 @@ NEXT_HYPERCALL(arch_6)
>  #endif
>       ELFNOTE(Xen, XEN_ELFNOTE_ENTRY,          _ASM_PTR startup_xen)
>       ELFNOTE(Xen, XEN_ELFNOTE_HYPERCALL_PAGE, _ASM_PTR hypercall_page)
> -     ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .asciz 
> "!writable_page_tables|pae_pgdir_above_4gb")
> +     ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .asciz 
> "!writable_page_tables|pae_pgdir_above_4gb"FEATURES_PVH)
>       ELFNOTE(Xen, XEN_ELFNOTE_PAE_MODE,       .asciz "yes")
>       ELFNOTE(Xen, XEN_ELFNOTE_LOADER,         .asciz "generic")
>       ELFNOTE(Xen, XEN_ELFNOTE_L1_MFN_VALID,

Considering that the PVH capability ends up in an ELF note, the kconfig
symbol is actually useful at least for debugging: it is the only way to
disable it from the guest side. However I would imaging that Xen would
always provide an option to disable PVH features in a VM or dom0.


> diff --git a/include/xen/interface/memory.h b/include/xen/interface/memory.h
> index d8e33a9..425911f 100644
> --- a/include/xen/interface/memory.h
> +++ b/include/xen/interface/memory.h
> @@ -169,7 +169,13 @@ struct xen_add_to_physmap {
>      /* Source mapping space. */
>  #define XENMAPSPACE_shared_info 0 /* shared info page */
>  #define XENMAPSPACE_grant_table 1 /* grant table page */
> -    unsigned int space;
> +#define XENMAPSPACE_gmfn        2 /* GMFN */
> +#define XENMAPSPACE_gmfn_range  3 /* GMFN range */
> +#define XENMAPSPACE_gmfn_foreign 4 /* GMFN from another guest */
> +    uint16_t space;
> +    domid_t foreign_domid;         /* IFF XENMAPSPACE_gmfn_foreign */
> +
> +#define XENMAPIDX_grant_table_status 0x80000000
>  
>      /* Index into source mapping space. */
>      unsigned long idx;
> @@ -237,4 +243,20 @@ DEFINE_GUEST_HANDLE_STRUCT(xen_memory_map);
>   * during a driver critical region.
>   */
>  extern spinlock_t xen_reservation_lock;
> +
> +/*
> + * Unmaps the page appearing at a particular GPFN from the specified guest's
> + * pseudophysical address space.
> + * arg == addr of xen_remove_from_physmap_t.
> + */
> +#define XENMEM_remove_from_physmap      15
> +struct xen_remove_from_physmap {
> +    /* Which domain to change the mapping for. */
> +    domid_t domid;
> +
> +    /* GPFN of the current mapping of the page. */
> +    xen_pfn_t gpfn;
> +};
> +DEFINE_GUEST_HANDLE_STRUCT(xen_remove_from_physmap);
> +
>  #endif /* __XEN_PUBLIC_MEMORY_H__ */

these bits have been submitted separately by Ian, if I am not mistaken.


> diff --git a/include/xen/interface/physdev.h b/include/xen/interface/physdev.h
> index 9ce788d..3b9d5b6 100644
> --- a/include/xen/interface/physdev.h
> +++ b/include/xen/interface/physdev.h
> @@ -258,6 +258,16 @@ struct physdev_pci_device {
>      uint8_t devfn;
>  };
>  
> +#define PHYSDEVOP_pvh_map_iomem        30

I would just call this PHYSDEVOP_map_iomem, we might use it on non-PVH
guests as well one day.


> +struct physdev_map_iomem {
> +    /* IN */
> +    uint64_t first_gfn;
> +    uint64_t first_mfn;
> +    uint32_t nr_mfns;
> +    uint32_t add_mapping;        /* 1 == add mapping;  0 == unmap */
> +
> +};
> +
>  /*
>   * Notify that some PIRQ-bound event channels have been unmasked.
>   * ** This command is obsolete since interface version 0x00030202 and is **
> -- 
> 1.7.2.3
> 
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