Re: [Xen-devel] [PATCH v4 02/14] libxc: Prepare a start info structure for hvmloader

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Mar 14, 2016 at 05:55:37PM +0000, Anthony PERARD wrote:
> ... and load BIOS into guest memory.
> 
> This adds a new firmware module, bios_module. It is
> loaded in the guest memory and final location is provided to hvmloader
> via the hvm_start_info struct.
> 
> This patch create the hvm_start_info struct for HVM guest that have a
> device model, so this is now common code with HVM guest without device
> model.

CC-ing Boris and Roger since this impact the PVH code.

And therefore not snipping the code so they can see it in its full
glory.

> 
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> ---
> Change in V4:
> - change title to suggest the change of beavior
> - remove code to load acpi tables (dsdt)
> - Update public/xen.h about hvm_start_info available on other HVM guest
>   in %ebx.
> 
> Change in V3:
> - rename acpi_table_module to full_acpi_module.
> - factorise module loading, using new function to load existing optinal
>   module, this should not change anything
> - should now use the same code to loads modules as for HVMlite VMs.
>   this avoid duplication of code.
> - no more generic cmdline with a list of modules, each module have its name
>   in the module specific cmdline.
> - scope change for common code between hvmlite and hvmloader
> ---
>  tools/libxc/include/xc_dom.h   |   3 +
>  tools/libxc/xc_dom_hvmloader.c |   2 +
>  tools/libxc/xc_dom_x86.c       | 132 
> ++++++++++++++++++++++++++++-------------
>  xen/include/public/xen.h       |   2 +-
>  4 files changed, 96 insertions(+), 43 deletions(-)
> 
> diff --git a/tools/libxc/include/xc_dom.h b/tools/libxc/include/xc_dom.h
> index 6ebe946..93f894c 100644
> --- a/tools/libxc/include/xc_dom.h
> +++ b/tools/libxc/include/xc_dom.h
> @@ -209,6 +209,9 @@ struct xc_dom_image {
>      /* If unset disables the setup of the IOREQ pages. */
>      bool device_model;
>  
> +    /* BIOS passed to HVMLOADER */
> +    struct xc_hvm_firmware_module bios_module;
> +
>      /* Extra ACPI tables passed to HVMLOADER */
>      struct xc_hvm_firmware_module acpi_module;
>  
> diff --git a/tools/libxc/xc_dom_hvmloader.c b/tools/libxc/xc_dom_hvmloader.c
> index 7cf5854..606351a 100644
> --- a/tools/libxc/xc_dom_hvmloader.c
> +++ b/tools/libxc/xc_dom_hvmloader.c
> @@ -167,6 +167,8 @@ static int modules_init(struct xc_dom_image *dom)
>  {
>      int rc;
>  
> +    rc = module_init_one(dom, &dom->bios_module, "bios module");
> +    if ( rc ) goto err;
>      rc = module_init_one(dom, &dom->acpi_module, "acpi module");
>      if ( rc ) goto err;
>      rc = module_init_one(dom, &dom->smbios_module, "smbios module");
> diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
> index bdec40a..9c56d55 100644
> --- a/tools/libxc/xc_dom_x86.c
> +++ b/tools/libxc/xc_dom_x86.c
> @@ -69,6 +69,9 @@
>  #define round_up(addr, mask)     ((addr) | (mask))
>  #define round_pg_up(addr)  (((addr) + PAGE_SIZE_X86 - 1) & ~(PAGE_SIZE_X86 - 
> 1))
>  
> +#define HVMLOADER_MODULE_MAX_COUNT 1
> +#define HVMLOADER_MODULE_NAME_SIZE 10
> +
>  struct xc_dom_params {
>      unsigned levels;
>      xen_vaddr_t vaddr_mask;
> @@ -590,6 +593,7 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
>      xen_pfn_t special_array[X86_HVM_NR_SPECIAL_PAGES];
>      xen_pfn_t ioreq_server_array[NR_IOREQ_SERVER_PAGES];
>      xc_interface *xch = dom->xch;
> +    size_t start_info_size = sizeof(struct hvm_start_info);
>  
>      /* Allocate and clear special pages. */
>      for ( i = 0; i < X86_HVM_NR_SPECIAL_PAGES; i++ )
> @@ -624,8 +628,6 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
>  
>      if ( !dom->device_model )
>      {
> -        size_t start_info_size = sizeof(struct hvm_start_info);
> -
>          if ( dom->cmdline )
>          {
>              dom->cmdline_size = ROUNDUP(strlen(dom->cmdline) + 1, 8);
> @@ -635,17 +637,26 @@ static int alloc_magic_pages_hvm(struct xc_dom_image 
> *dom)
>          /* Limited to one module. */
>          if ( dom->ramdisk_blob )
>              start_info_size += sizeof(struct hvm_modlist_entry);
> -
> -        rc = xc_dom_alloc_segment(dom, &dom->start_info_seg,
> -                                  "HVMlite start info", 0, start_info_size);
> -        if ( rc != 0 )
> -        {
> -            DOMPRINTF("Unable to reserve memory for the start info");
> -            goto out;
> -        }
>      }
>      else
>      {
> +        start_info_size +=
> +            sizeof(struct hvm_modlist_entry) * HVMLOADER_MODULE_MAX_COUNT;
> +        /* Add extra space to write modules name */
> +        start_info_size +=
> +            HVMLOADER_MODULE_NAME_SIZE * HVMLOADER_MODULE_MAX_COUNT;

What about \0 ? Ah, the strncpy we use adds \0 byte. But it would be nice
to mention that somewhere. Perhaps mention:

The HVMLOADER_MODULE_NAME_SIZE accounts for NUL byte?

> +    }
> +
> +    rc = xc_dom_alloc_segment(dom, &dom->start_info_seg,
> +                              "HVMlite start info", 0, start_info_size);
> +    if ( rc != 0 )
> +    {
> +        DOMPRINTF("Unable to reserve memory for the start info");
> +        goto out;
> +    }
> +
> +    if ( dom->device_model )
> +    {
>          /*
>           * Allocate and clear additional ioreq server pages. The default
>           * server will use the IOREQ and BUFIOREQ special pages above.
> @@ -1696,39 +1707,68 @@ static int alloc_pgtables_hvm(struct xc_dom_image 
> *dom)
>      return 0;
>  }
>  
> +static void add_module_to_list(struct xc_dom_image *dom,
> +                               struct xc_hvm_firmware_module *module,
> +                               const char *name,
> +                               struct hvm_modlist_entry *modlist,
> +                               struct hvm_start_info *start_info)
> +{
> +    uint32_t index = start_info->nr_modules;
> +    if ( module->length == 0 )
> +        return;
> +
> +    assert(start_info->nr_modules < HVMLOADER_MODULE_MAX_COUNT);
> +    assert(strnlen(name, HVMLOADER_MODULE_NAME_SIZE)
> +           < HVMLOADER_MODULE_NAME_SIZE);
> +
> +    modlist[index].paddr = module->guest_addr_out;
> +    modlist[index].size = module->length;
> +    strncpy((char*)(modlist + HVMLOADER_MODULE_MAX_COUNT)
> +            + HVMLOADER_MODULE_NAME_SIZE * index,
> +            name, HVMLOADER_MODULE_NAME_SIZE);
> +    modlist[index].cmdline_paddr =
> +        (dom->start_info_seg.pfn << PAGE_SHIFT) +
> +        ((uintptr_t)modlist - (uintptr_t)start_info) +
> +        sizeof(struct hvm_modlist_entry) * HVMLOADER_MODULE_MAX_COUNT +
> +        HVMLOADER_MODULE_NAME_SIZE * index;

That looks right, but boy it takes a bit of thinking to
make sure it is right. Perhaps put a comment outlining where
it ought to be (so folks reading the first time can feel
OK they got it right?)
> +
> +    start_info->nr_modules++;
> +}
> +
>  static int bootlate_hvm(struct xc_dom_image *dom)
>  {
>      uint32_t domid = dom->guest_domid;
>      xc_interface *xch = dom->xch;
> +    struct hvm_start_info *start_info;
> +    size_t start_info_size;
> +    void *start_page;
> +    struct hvm_modlist_entry *modlist;
>  
> -    if ( !dom->device_model )
> -    {
> -        struct hvm_start_info *start_info;
> -        size_t start_info_size;
> -        void *start_page;
> -
> -        start_info_size = sizeof(*start_info) + dom->cmdline_size;
> -        if ( dom->ramdisk_blob )
> -            start_info_size += sizeof(struct hvm_modlist_entry);
> +    start_info_size = sizeof(*start_info) + dom->cmdline_size;
> +    if ( dom->ramdisk_blob )
> +        start_info_size += sizeof(struct hvm_modlist_entry);
>  
> -        if ( start_info_size >
> -             dom->start_info_seg.pages << XC_DOM_PAGE_SHIFT(dom) )
> -        {
> -            DOMPRINTF("Trying to map beyond start_info_seg");
> -            return -1;
> -        }
> +    if ( start_info_size >
> +         dom->start_info_seg.pages << XC_DOM_PAGE_SHIFT(dom) )
> +    {
> +        DOMPRINTF("Trying to map beyond start_info_seg");
> +        return -1;
> +    }
>  
> -        start_page = xc_map_foreign_range(xch, domid, start_info_size,
> -                                          PROT_READ | PROT_WRITE,
> -                                          dom->start_info_seg.pfn);
> -        if ( start_page == NULL )
> -        {
> -            DOMPRINTF("Unable to map HVM start info page");
> -            return -1;
> -        }
> +    start_page = xc_map_foreign_range(xch, domid, start_info_size,
> +                                      PROT_READ | PROT_WRITE,
> +                                      dom->start_info_seg.pfn);
> +    if ( start_page == NULL )
> +    {
> +        DOMPRINTF("Unable to map HVM start info page");
> +        return -1;
> +    }
>  
> -        start_info = start_page;
> +    start_info = start_page;
> +    modlist = start_page + sizeof(*start_info) + dom->cmdline_size;
>  
> +    if ( !dom->device_model )
> +    {
>          if ( dom->cmdline )
>          {
>              char *cmdline = start_page + sizeof(*start_info);
> @@ -1740,22 +1780,30 @@ static int bootlate_hvm(struct xc_dom_image *dom)
>  
>          if ( dom->ramdisk_blob )
>          {
> -            struct hvm_modlist_entry *modlist =
> -                start_page + sizeof(*start_info) + dom->cmdline_size;
>  
>              modlist[0].paddr = dom->ramdisk_seg.vstart - 
> dom->parms.virt_base;
>              modlist[0].size = dom->ramdisk_seg.vend - 
> dom->ramdisk_seg.vstart;
> -            start_info->modlist_paddr = (dom->start_info_seg.pfn << 
> PAGE_SHIFT) +
> -                                ((uintptr_t)modlist - (uintptr_t)start_info);
>              start_info->nr_modules = 1;
>          }
> -
> -        start_info->magic = XEN_HVM_START_MAGIC_VALUE;
> -
> -        munmap(start_page, start_info_size);
>      }
>      else
>      {
> +        add_module_to_list(dom, &dom->bios_module, "bios",
> +                           modlist, start_info);
> +    }
> +
> +    if ( start_info->nr_modules )
> +    {
> +        start_info->modlist_paddr = (dom->start_info_seg.pfn << PAGE_SHIFT) +
> +                            ((uintptr_t)modlist - (uintptr_t)start_info);
> +    }
> +
> +    start_info->magic = XEN_HVM_START_MAGIC_VALUE;
> +
> +    munmap(start_page, start_info_size);
> +
> +    if ( dom->device_model )
> +    {
>          void *hvm_info_page;
>  
>          if ( (hvm_info_page = xc_map_foreign_range(
> diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
> index 64ba7ab..1cfec5c 100644
> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -798,7 +798,7 @@ struct start_info {
>  typedef struct start_info start_info_t;
>  
>  /*
> - * Start of day structure passed to PVH guests in %ebx.
> + * Start of day structure passed to PVH guests and to HVM guests in %ebx.
>   *
>   * NOTE: nothing will be loaded at physical address 0, so a 0 value in any
>   * of the address fields should be treated as not present.
> -- 
> Anthony PERARD
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel

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