Re: [Xen-devel] [PATCH v4 11/18] x86/mem_sharing: ASSERT that p2m_set_entry succeeds

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.01.2020 18:14, Tamas K Lengyel wrote:
> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
> ---
>  xen/arch/x86/mm/mem_sharing.c | 42 +++++++++++++++++------------------
>  1 file changed, 21 insertions(+), 21 deletions(-)
> 
> diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
> index 93e7605900..3f36cd6bbc 100644
> --- a/xen/arch/x86/mm/mem_sharing.c
> +++ b/xen/arch/x86/mm/mem_sharing.c
> @@ -1117,11 +1117,19 @@ int add_to_physmap(struct domain *sd, unsigned long 
> sgfn, shr_handle_t sh,
>          goto err_unlock;
>      }
>  
> +    /*
> +     * Must succeed, we just read the entry and hold the p2m lock
> +     * via get_two_gfns.
> +     */
>      ret = p2m_set_entry(p2m, _gfn(cgfn), smfn, PAGE_ORDER_4K,
>                          p2m_ram_shared, a);
> +    ASSERT(!ret);

And there's no risk of -ENOMEM because of needing to split a
larger order page? At the very least the reasoning in the
comment would need further extending.

Jan

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