Re: [PATCH 5/7] x86/mm: Carve steal_linear_address() out of replace_grant_host_mapping()

[Wei Liu <wei.liu2@citrix.com>]

On Tue, Sep 12, 2017 at 01:14:44PM +0100, Andrew Cooper wrote:
> Document its curious semantics.
> 
> No functional change.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> ---
>  xen/arch/x86/mm.c | 105 ++++++++++++++++++++++++++++++------------------------
>  1 file changed, 58 insertions(+), 47 deletions(-)
> 
> diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
> index e08b4a8..afd98d9 100644
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -4075,14 +4075,68 @@ int create_grant_pv_mapping(uint64_t addr, unsigned long frame,
>      return rc;
>  }
>  
> -int replace_grant_pv_mapping(uint64_t addr, unsigned long frame,
> -                             uint64_t new_addr, unsigned int flags)
> +/*
> + * This exists soley for implementing GNTABOP_unmap_and_replace, the ABI of
> + * which is bizare.  This GNTTABOP isn't used any more, but was used by

Should be "bizarre".

> + * classic-xen kernels and PVOps Linux before the M2P_OVERRIDE infrastructure
> + * was replaced with something which actually worked.
> + *
> + * Look up the L1e mapping linear, and zap it.  Return the L1e via *out.
> + * Returns a boolean indicating success.  If success, the caller is
> + * responsible for calling put_page_from_l1e().
> + */

Can't say much about the history; code-wise:

Reviewed-by: Wei Liu <wei.liu2@citrix.com>

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