Re: [PATCH] libxc: Don't call set_pod_target in case of previous memory failure

[George Dunlap <george.dunlap@eu.citrix.com>]

On 26/07/12 18:02, George Dunlap wrote:
> # HG changeset patch
> # User George Dunlap <george.dunlap@eu.citrix.com>
> # Date 1343320554 -3600
> # Node ID f7997e838585d4f40ae5dc14541f8efe71ce3c55
> # Parent  b63d4890d15e74b4c8ca45607563245076b3e770
> libxc: Don't call set_pod_target in case of previous memory failure
>
> The while() loop in the memory allocation section of the hvm builder
> is where the actual check for failure of memory alloction happens.  If
> the domain is being built in PoD mode, however, this value may be
> clobbered by a call to xc_domain_set_pod_target() before erroring out.
> There is a very small chance that after xc_domain_populate_physmap()
> fails, that somehow set_pod_target() will succeed, leaving a domain
> with only a partially created address space.
>
> This patch modifies the builder to check that there have not been any
> errors so far before calling xc_domain_set_pod_target().
>
> Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
>
> diff --git a/tools/libxc/xc_hvm_build_x86.c b/tools/libxc/xc_hvm_build_x86.c
> --- a/tools/libxc/xc_hvm_build_x86.c
> +++ b/tools/libxc/xc_hvm_build_x86.c
> @@ -311,7 +311,7 @@ static int setup_guest(xc_interface *xch
>       /* Subtract 0x20 from target_pages for the VGA "hole".  Xen will
>        * adjust the PoD cache size so that domain tot_pages will be
>        * target_pages - 0x20 after this call. */
> -    if ( pod_mode )
> +    if ( rc != 0 && pod_mode )
Gah, sorry -- got the polarity wrong on this one... please ignore...
  -George
>           rc = xc_domain_set_pod_target(xch, dom, target_pages - 0x20,
>                                         NULL, NULL, NULL);
>