Re: [Xen-devel] [PATCH v4 4/4] libxc: Pass e820 map to HVM/PVH guests via hvm_start_info

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Mar 20, 2018 at 09:50:52AM -0700, Maran Wilson wrote:
> From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Signed-off-by: Maran Wilson <maran.wilson@xxxxxxxxxx>
> ---
>  tools/libxc/xc_dom_x86.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
> index 0b65dab..b2d8403 100644
> --- a/tools/libxc/xc_dom_x86.c
> +++ b/tools/libxc/xc_dom_x86.c
> @@ -35,6 +35,8 @@
>  #include <xen/arch-x86/hvm/start_info.h>
>  #include <xen/io/protocols.h>
>  
> +#include <xen-tools/libs.h>
> +
>  #include "xg_private.h"
>  #include "xc_dom.h"
>  #include "xenctrl.h"
> @@ -640,6 +642,8 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
>              dom->cmdline_size = ROUNDUP(strlen(dom->cmdline) + 1, 8);
>              start_info_size += dom->cmdline_size;
>          }
> +
> +        start_info_size += dom->e820_entries * sizeof(*(dom->e820));

This is not correct because sizeof(struct e820entry) != sizeof(struct
hvm_modlist_entry) AFAICT. This should instead be sizeof(struct
hvm_modlist_entry).

>      }
>      else
>      {
> @@ -1666,8 +1670,9 @@ 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;
> +    size_t start_info_size, modsize;
>      struct hvm_modlist_entry *modlist;
> +    struct hvm_memmap_table_entry *memmap;
>      unsigned int i;
>  
>      start_info_size = sizeof(*start_info) + dom->cmdline_size;
> @@ -1731,7 +1736,29 @@ static int bootlate_hvm(struct xc_dom_image *dom)
>                              ((uintptr_t)modlist - (uintptr_t)start_info);
>      }
>  
> +    /*
> +     * Check a couple of XEN_HVM_MEMMAP_TYPEs to verify consistency with
> +     * their corresponding e820 numerical values.
> +     */
> +    BUILD_BUG_ON(XEN_HVM_MEMMAP_TYPE_RAM != E820_RAM);
> +    BUILD_BUG_ON(XEN_HVM_MEMMAP_TYPE_ACPI != E820_ACPI);
> +
> +    modsize = HVMLOADER_MODULE_MAX_COUNT *
> +        (sizeof(*modlist) + HVMLOADER_MODULE_CMDLINE_SIZE);

Hm, I'm not sure this is fully correct, but I think there are previous
issues in this area.

The mapped area (start_info) is of size sizeof(*start_info) +
dom->cmdline_size + sizeof(struct hvm_modlist_entry) *
dom->num_modules. Yet here you seem to assume num_modules ==
HVMLOADER_MODULE_MAX_COUNT?

Also the initial space calculation doesn't seem to take
HVMLOADER_MODULE_CMDLINE_SIZE into account at all.

And cmdline_paddr seems to be set to point to garbage if cmdline is not
set.

Or am I missing something?

Adding Jonathan Ludlam and Anthony PERARD who are the ones that added
this code.

Thanks, Roger.

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