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Re: [Xen-devel] [PATCH 2/2] dom_cow is needed for mem-sharing only
- To: Jan Beulich <JBeulich@xxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 31 May 2019 10:13:38 -0700
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, WeiLiu <wl@xxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, Julien Grall <julien.grall@xxxxxxx>, Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
- Delivery-date: Fri, 31 May 2019 17:13:51 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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On 31/05/2019 02:35, Jan Beulich wrote:
> A couple of adjustments are needed to code checking for dom_cow, but
> since there are pretty few it is probably better to adjust those than
> to set up and keep around a never used domain.
>
> Take the opportunity and tighten a BUG_ON() in emul-priv-op.c:read_cr().
> (Arguably this perhaps shouldn't be a BUG_ON() in the first place.)
Yes - it should be ASSERT_UNREACHABLE()/domain_crash()
I'm not fussed if this done as part of this patch, or split out
separately. It almost doesn't seem worth splitting out.
> --- a/xen/include/xen/mm.h
> +++ b/xen/include/xen/mm.h
> @@ -644,6 +644,9 @@ static inline void filtered_flush_tlb_ma
>
> /* Private domain structs for DOMID_XEN, DOMID_IO, etc. */
> extern struct domain *dom_xen, *dom_io, *dom_cow;
> +#ifndef CONFIG_HAS_MEM_SHARING
> +# define dom_cow NULL
> +#endif
>
> enum XENSHARE_flags {
> SHARE_rw,
>
>
>
What is wrong with
#ifdef CONFIG_HAS_MEM_SHARING
extern struct domain *dom_cow;
#else
# define dom_cow NULL
#endif
which is how we usually express things like this? Sure, its a tiny bit
longer to write, but it is easier to follow.
~Andrew
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