Re: [Xen-devel] [PATCH v3 38/38] arm/p2m: Add test of xc_altp2m_change_gfn

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Aug 17, 2016 at 12:17:14AM +0200, Sergej Proskurin wrote:
> This commit extends xen-access by a simple test of the functionality
> provided by "xc_altp2m_change_gfn". The idea is to dynamically remap a
> trapping gfn to another mfn, which holds the same content as the
> original mfn. On success, the guest will continue to run. Subsequent
> altp2m access violations will trap into Xen and be forced by xen-access
> to switch to the default view (altp2m[0]) as before. The introduced test
> can be invoked by providing the argument "altp2m_remap".
> 
> Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
> ---
> Cc: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> Cc: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
> v3: Cosmetic fixes in "xenaccess_copy_gfn" and "xenaccess_change_gfn".
> 
>     Added munmap in "copy_gfn" in the second error case.
> 
>     Added option "altp2m_remap" selecting the altp2m-remap test.
> ---
>  tools/tests/xen-access/xen-access.c | 162 
> +++++++++++++++++++++++++++++++++++-
>  1 file changed, 158 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/tests/xen-access/xen-access.c 
> b/tools/tests/xen-access/xen-access.c
> index eafd7d6..5909a8a 100644
> --- a/tools/tests/xen-access/xen-access.c
> +++ b/tools/tests/xen-access/xen-access.c
> @@ -38,6 +38,7 @@
>  #include <sys/mman.h>
>  #include <sys/poll.h>
>  
> +#define XC_WANT_COMPAT_MAP_FOREIGN_API

I know Razvan already acked this, but general you shouldn't use the
COMPAT APIs. You should use libs/foreignmemory library, which is a
stable library.

>  #include <xenctrl.h>
>  #include <xenevtchn.h>
>  #include <xen/vm_event.h>
> @@ -49,6 +50,8 @@
>  #define START_PFN 0ULL
>  #endif
>  
> +#define INVALID_GFN ~(0UL)
> +
>  #define DPRINTF(a, b...) fprintf(stderr, a, ## b)
>  #define ERROR(a, b...) fprintf(stderr, a "\n", ## b)
>  #define PERROR(a, b...) fprintf(stderr, a ": %s\n", ## b, strerror(errno))
> @@ -72,9 +75,14 @@ typedef struct xenaccess {
>      xen_pfn_t max_gpfn;
>  
>      vm_event_t vm_event;
> +
> +    unsigned int ap2m_idx;
> +    xen_pfn_t gfn_old;
> +    xen_pfn_t gfn_new;
>  } xenaccess_t;
>  
>  static int interrupted;
> +static int gfn_changed = 0;
>  bool evtchn_bind = 0, evtchn_open = 0, mem_access_enable = 0;
>  
>  static void close_handler(int sig)
> @@ -82,6 +90,100 @@ static void close_handler(int sig)
>      interrupted = sig;
>  }
>  
> +static int xenaccess_copy_gfn(xc_interface *xch,
> +                              domid_t domain_id,
> +                              xen_pfn_t dst_gfn,
> +                              xen_pfn_t src_gfn)
> +{
> +    void *src_vaddr = NULL;
> +    void *dst_vaddr = NULL;
> +
> +    src_vaddr = xc_map_foreign_range(xch, domain_id, XC_PAGE_SIZE,
> +                                     PROT_READ, src_gfn);
> +    if ( src_vaddr == MAP_FAILED || src_vaddr == NULL)
> +        return -1;
> +
> +    dst_vaddr = xc_map_foreign_range(xch, domain_id, XC_PAGE_SIZE,
> +                                     PROT_WRITE, dst_gfn);

You can have a look at libxc/xc_foreign_memory.c for how to replace this
legacy call with the new function.

Wei.

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