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Re: [PATCH v2] x86/domain: adjust limitation on shared_info allocation below 4G


  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Wed, 4 Feb 2026 16:32:25 +0100
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  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Wed, 04 Feb 2026 15:32:32 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 04.02.2026 16:12, Andrew Cooper wrote:
> On 04/02/2026 3:01 pm, Roger Pau Monné wrote:
>>>> +        share_xen_page_with_guest(virt_to_page(d->shared_info), d, 
>>>> SHARE_rw);
>>>> +        /* Ensure all references to the old shared_info page are dropped. 
>>>> */
>>>> +        for_each_vcpu( d, v )
>>>> +            vcpu_info_reset(v);
>>> switch_compat() can only occur on a domain with no memory.  How can we
>>> have outstanding references?
>> As Jan pointed out, it's not references, but stashed pointers to the
>> previous shared_info page.  I've used the wrong wording here.
> 
> Yes, I saw that thread, but my question still stands.
> 
> How can there be any this early in the domain's lifecycle?

Can't (aren't) vCPU-s added ahead of adding memory?

Jan



 


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