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Re: [PATCH 5/9] x86/mtrr: use memory_type_changed() in hvm_set_mem_pinned_cacheattr()


  • To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Fri, 16 May 2025 10:02:22 +0200
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Fri, 16 May 2025 08:02:32 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 16.05.2025 09:48, Roger Pau Monné wrote:
> Overall, I have the impression hvm_set_mem_pinned_cacheattr() should
> only be used while building a domain, and hence the flush can likely
> be skipped unconditionally, regardless of the type changes.

See my patch submission, which had this remark:

"Is it really sensible to add/remove ranges once the guest is already
 running? (If it is, limiting the scope of the flush would be nice, but
 would require knowing dirtyness for the domain wrt the caches, which
 currently we don't track.)"

As apparently we both agree, why don't we reject requests post-creation
then, and drop the flush? The one thing I'm uncertain about is whether
the DM would actually have carried out the operation strictly ahead of
the domain being first un-paused.

Jan



 


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