Re: [PATCH v4 5/5] tools/libxc: make use of domain context SHARED_INFO record...

[Ian Jackson <ian.jackson@xxxxxxxxxx>]

Paul Durrant writes ("[PATCH v4 5/5] tools/libxc: make use of domain context 
SHARED_INFO record..."):
> ... in the save/restore code.
> 
> This patch replaces direct mapping of the shared_info_frame (retrieved
> using XEN_DOMCTL_getdomaininfo) with save/load of the domain context
> SHARED_INFO record.
> 
> No modifications are made to the definition of the migration stream at
> this point. Subsequent patches will define a record in the libxc domain
> image format for passing domain context and convert the save/restore code
> to use that.

Andy, I think this needs your option.

Thanks,
Ian.

> Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> ---
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Wei Liu <wl@xxxxxxx>
> 
> v3:
>  - Moved basic get/set domain context functions to common code
> 
> v2:
>  - Re-based (now making use of DOMAIN_SAVE_FLAG_IGNORE)
> ---
>  tools/libxc/xc_sr_common.c         | 67 +++++++++++++++++++++++++++
>  tools/libxc/xc_sr_common.h         | 11 ++++-
>  tools/libxc/xc_sr_common_x86_pv.c  | 74 ++++++++++++++++++++++++++++++
>  tools/libxc/xc_sr_common_x86_pv.h  |  3 ++
>  tools/libxc/xc_sr_restore_x86_pv.c | 26 ++++-------
>  tools/libxc/xc_sr_save_x86_pv.c    | 43 ++++++++---------
>  tools/libxc/xg_save_restore.h      |  1 +
>  7 files changed, 181 insertions(+), 44 deletions(-)
> 
> diff --git a/tools/libxc/xc_sr_common.c b/tools/libxc/xc_sr_common.c
> index dd9a11b4b5..1acb3765aa 100644
> --- a/tools/libxc/xc_sr_common.c
> +++ b/tools/libxc/xc_sr_common.c
> @@ -138,6 +138,73 @@ int read_record(struct xc_sr_context *ctx, int fd, 
> struct xc_sr_record *rec)
>      return 0;
>  };
>  
> +int get_domain_context(struct xc_sr_context *ctx)
> +{
> +    xc_interface *xch = ctx->xch;
> +    size_t len = 0;
> +    int rc;
> +
> +    if ( ctx->domain_context.buffer )
> +    {
> +        ERROR("Domain context already present");
> +        return -1;
> +    }
> +
> +    rc = xc_domain_getcontext(xch, ctx->domid, NULL, &len);
> +    if ( rc < 0 )
> +    {
> +        PERROR("Unable to get size of domain context");
> +        return -1;
> +    }
> +
> +    ctx->domain_context.buffer = malloc(len);
> +    if ( !ctx->domain_context.buffer )
> +    {
> +        PERROR("Unable to allocate memory for domain context");
> +        return -1;
> +    }
> +
> +    rc = xc_domain_getcontext(xch, ctx->domid, ctx->domain_context.buffer,
> +                              &len);
> +    if ( rc < 0 )
> +    {
> +        PERROR("Unable to get domain context");
> +        return -1;
> +    }
> +
> +    ctx->domain_context.len = len;
> +
> +    return 0;
> +}
> +
> +int set_domain_context(struct xc_sr_context *ctx)
> +{
> +    xc_interface *xch = ctx->xch;
> +    int rc;
> +
> +    if ( !ctx->domain_context.buffer )
> +    {
> +        ERROR("Domain context not present");
> +        return -1;
> +    }
> +
> +    rc = xc_domain_setcontext(xch, ctx->domid, ctx->domain_context.buffer,
> +                              ctx->domain_context.len);
> +
> +    if ( rc < 0 )
> +    {
> +        PERROR("Unable to set domain context");
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +void common_cleanup(struct xc_sr_context *ctx)
> +{
> +    free(ctx->domain_context.buffer);
> +}
> +
>  static void __attribute__((unused)) build_assertions(void)
>  {
>      BUILD_BUG_ON(sizeof(struct xc_sr_ihdr) != 24);
> diff --git a/tools/libxc/xc_sr_common.h b/tools/libxc/xc_sr_common.h
> index 5dd51ccb15..0d61978b08 100644
> --- a/tools/libxc/xc_sr_common.h
> +++ b/tools/libxc/xc_sr_common.h
> @@ -208,6 +208,11 @@ struct xc_sr_context
>  
>      xc_dominfo_t dominfo;
>  
> +    struct {
> +        void *buffer;
> +        unsigned int len;
> +    } domain_context;
> +
>      union /* Common save or restore data. */
>      {
>          struct /* Save data. */
> @@ -314,7 +319,7 @@ struct xc_sr_context
>                  /* The guest pfns containing the p2m leaves */
>                  xen_pfn_t *p2m_pfns;
>  
> -                /* Read-only mapping of guests shared info page */
> +                /* Pointer to shared_info (located in context buffer) */
>                  shared_info_any_t *shinfo;
>  
>                  /* p2m generation count for verifying validity of local p2m. 
> */
> @@ -425,6 +430,10 @@ int read_record(struct xc_sr_context *ctx, int fd, 
> struct xc_sr_record *rec);
>  int populate_pfns(struct xc_sr_context *ctx, unsigned int count,
>                    const xen_pfn_t *original_pfns, const uint32_t *types);
>  
> +int get_domain_context(struct xc_sr_context *ctx);
> +int set_domain_context(struct xc_sr_context *ctx);
> +void common_cleanup(struct xc_sr_context *ctx);
> +
>  #endif
>  /*
>   * Local variables:
> diff --git a/tools/libxc/xc_sr_common_x86_pv.c 
> b/tools/libxc/xc_sr_common_x86_pv.c
> index d3d425cb82..69d9b142b8 100644
> --- a/tools/libxc/xc_sr_common_x86_pv.c
> +++ b/tools/libxc/xc_sr_common_x86_pv.c
> @@ -182,6 +182,80 @@ int x86_pv_map_m2p(struct xc_sr_context *ctx)
>      return rc;
>  }
>  
> +int x86_pv_get_shinfo(struct xc_sr_context *ctx)
> +{
> +    xc_interface *xch = ctx->xch;
> +    unsigned int off = 0;
> +    int rc;
> +
> +#define GET_PTR(_x)                                                         \
> +    do {                                                                    \
> +        if ( ctx->domain_context.len - off < sizeof(*(_x)) )                \
> +        {                                                                   \
> +            ERROR("Need another %lu bytes of context, only %u available\n", \
> +                  sizeof(*(_x)), ctx->domain_context.len - off);            \
> +            return -1;                                                      \
> +        }                                                                   \
> +        (_x) = ctx->domain_context.buffer + off;                            \
> +    } while (false);
> +
> +    rc = get_domain_context(ctx);
> +    if ( rc )
> +        return rc;
> +
> +    for ( ; ; )
> +    {
> +        struct domain_save_descriptor *desc;
> +
> +        GET_PTR(desc);
> +
> +        off += sizeof(*desc);
> +
> +        switch (desc->typecode)
> +        {
> +        case DOMAIN_SAVE_CODE(SHARED_INFO):
> +        {
> +            DOMAIN_SAVE_TYPE(SHARED_INFO) *s;
> +
> +            GET_PTR(s);
> +
> +            ctx->x86.pv.shinfo = (shared_info_any_t *)s->buffer;
> +            break;
> +        }
> +        default:
> +            break;
> +        }
> +
> +        if ( desc->typecode == DOMAIN_SAVE_CODE(END) )
> +            break;
> +
> +        off += desc->length;
> +    }
> +
> +    if ( !ctx->x86.pv.shinfo )
> +    {
> +        ERROR("Failed to get SHARED_INFO\n");
> +        return -1;
> +    }
> +
> +    return 0;
> +
> +#undef GET_PTR
> +}
> +
> +int x86_pv_set_shinfo(struct xc_sr_context *ctx)
> +{
> +    xc_interface *xch = ctx->xch;
> +
> +    if ( !ctx->x86.pv.shinfo )
> +    {
> +        ERROR("SHARED_INFO buffer not present\n");
> +        return -1;
> +    }
> +
> +    return set_domain_context(ctx);
> +}
> +
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/tools/libxc/xc_sr_common_x86_pv.h 
> b/tools/libxc/xc_sr_common_x86_pv.h
> index 2ed03309af..01442f48fb 100644
> --- a/tools/libxc/xc_sr_common_x86_pv.h
> +++ b/tools/libxc/xc_sr_common_x86_pv.h
> @@ -97,6 +97,9 @@ int x86_pv_domain_info(struct xc_sr_context *ctx);
>   */
>  int x86_pv_map_m2p(struct xc_sr_context *ctx);
>  
> +int x86_pv_get_shinfo(struct xc_sr_context *ctx);
> +int x86_pv_set_shinfo(struct xc_sr_context *ctx);
> +
>  #endif
>  /*
>   * Local variables:
> diff --git a/tools/libxc/xc_sr_restore_x86_pv.c 
> b/tools/libxc/xc_sr_restore_x86_pv.c
> index 904ccc462a..21982a38ad 100644
> --- a/tools/libxc/xc_sr_restore_x86_pv.c
> +++ b/tools/libxc/xc_sr_restore_x86_pv.c
> @@ -865,7 +865,7 @@ static int handle_shared_info(struct xc_sr_context *ctx,
>      xc_interface *xch = ctx->xch;
>      unsigned int i;
>      int rc = -1;
> -    shared_info_any_t *guest_shinfo = NULL;
> +    shared_info_any_t *guest_shinfo;
>      const shared_info_any_t *old_shinfo = rec->data;
>  
>      if ( !ctx->x86.pv.restore.seen_pv_info )
> @@ -878,18 +878,14 @@ static int handle_shared_info(struct xc_sr_context *ctx,
>      {
>          ERROR("X86_PV_SHARED_INFO record wrong size: length %u"
>                ", expected 4096", rec->length);
> -        goto err;
> +        return -1;
>      }
>  
> -    guest_shinfo = xc_map_foreign_range(
> -        xch, ctx->domid, PAGE_SIZE, PROT_READ | PROT_WRITE,
> -        ctx->dominfo.shared_info_frame);
> -    if ( !guest_shinfo )
> -    {
> -        PERROR("Failed to map Shared Info at mfn %#lx",
> -               ctx->dominfo.shared_info_frame);
> -        goto err;
> -    }
> +    rc = x86_pv_get_shinfo(ctx);
> +    if ( rc )
> +        return rc;
> +
> +    guest_shinfo = ctx->x86.pv.shinfo;
>  
>      MEMCPY_FIELD(guest_shinfo, old_shinfo, vcpu_info, ctx->x86.pv.width);
>      MEMCPY_FIELD(guest_shinfo, old_shinfo, arch, ctx->x86.pv.width);
> @@ -904,13 +900,7 @@ static int handle_shared_info(struct xc_sr_context *ctx,
>  
>      MEMSET_ARRAY_FIELD(guest_shinfo, evtchn_mask, 0xff, ctx->x86.pv.width);
>  
> -    rc = 0;
> -
> - err:
> -    if ( guest_shinfo )
> -        munmap(guest_shinfo, PAGE_SIZE);
> -
> -    return rc;
> +    return x86_pv_set_shinfo(ctx);
>  }
>  
>  /* restore_ops function. */
> diff --git a/tools/libxc/xc_sr_save_x86_pv.c b/tools/libxc/xc_sr_save_x86_pv.c
> index f3ccf5bb4b..bf87789340 100644
> --- a/tools/libxc/xc_sr_save_x86_pv.c
> +++ b/tools/libxc/xc_sr_save_x86_pv.c
> @@ -9,25 +9,6 @@ static inline bool is_canonical_address(xen_vaddr_t vaddr)
>      return ((int64_t)vaddr >> 47) == ((int64_t)vaddr >> 63);
>  }
>  
> -/*
> - * Maps the guests shared info page.
> - */
> -static int map_shinfo(struct xc_sr_context *ctx)
> -{
> -    xc_interface *xch = ctx->xch;
> -
> -    ctx->x86.pv.shinfo = xc_map_foreign_range(
> -        xch, ctx->domid, PAGE_SIZE, PROT_READ, 
> ctx->dominfo.shared_info_frame);
> -    if ( !ctx->x86.pv.shinfo )
> -    {
> -        PERROR("Failed to map shared info frame at mfn %#lx",
> -               ctx->dominfo.shared_info_frame);
> -        return -1;
> -    }
> -
> -    return 0;
> -}
> -
>  /*
>   * Copy a list of mfns from a guest, accounting for differences between guest
>   * and toolstack width.  Can fail if truncation would occur.
> @@ -854,13 +835,26 @@ static int write_x86_pv_p2m_frames(struct xc_sr_context 
> *ctx)
>   */
>  static int write_shared_info(struct xc_sr_context *ctx)
>  {
> +    xc_interface *xch = ctx->xch;
>      struct xc_sr_record rec = {
>          .type = REC_TYPE_SHARED_INFO,
>          .length = PAGE_SIZE,
> -        .data = ctx->x86.pv.shinfo,
>      };
> +    int rc;
>  
> -    return write_record(ctx, &rec);
> +    if ( !(rec.data = calloc(1, PAGE_SIZE)) )
> +    {
> +        ERROR("Cannot allocate buffer for SHARED_INFO data");
> +        return -1;
> +    }
> +
> +    memcpy(rec.data, ctx->x86.pv.shinfo, sizeof(*ctx->x86.pv.shinfo));
> +
> +    rc = write_record(ctx, &rec);
> +
> +    free(rec.data);
> +
> +    return rc;
>  }
>  
>  /*
> @@ -1041,7 +1035,7 @@ static int x86_pv_setup(struct xc_sr_context *ctx)
>      if ( rc )
>          return rc;
>  
> -    rc = map_shinfo(ctx);
> +    rc = x86_pv_get_shinfo(ctx);
>      if ( rc )
>          return rc;
>  
> @@ -1112,12 +1106,11 @@ static int x86_pv_cleanup(struct xc_sr_context *ctx)
>      if ( ctx->x86.pv.p2m )
>          munmap(ctx->x86.pv.p2m, ctx->x86.pv.p2m_frames * PAGE_SIZE);
>  
> -    if ( ctx->x86.pv.shinfo )
> -        munmap(ctx->x86.pv.shinfo, PAGE_SIZE);
> -
>      if ( ctx->x86.pv.m2p )
>          munmap(ctx->x86.pv.m2p, ctx->x86.pv.nr_m2p_frames * PAGE_SIZE);
>  
> +    common_cleanup(ctx);
> +
>      return 0;
>  }
>  
> diff --git a/tools/libxc/xg_save_restore.h b/tools/libxc/xg_save_restore.h
> index 303081df0d..296b523963 100644
> --- a/tools/libxc/xg_save_restore.h
> +++ b/tools/libxc/xg_save_restore.h
> @@ -19,6 +19,7 @@
>  
>  #include <xen/foreign/x86_32.h>
>  #include <xen/foreign/x86_64.h>
> +#include <xen/save.h>
>  
>  /*
>  ** We process save/restore/migrate in batches of pages; the below
> -- 
> 2.20.1
>