Re: [PATCH 05/10] xen/arm: introduce alloc_staticmem_pages

From: Julien Grall <julien@xen.org>
To: Jan Beulich <jbeulich@suse.com>, Penny Zheng <penny.zheng@arm.com>
Cc: Bertrand.Marquis@arm.com, Wei.Chen@arm.com, nd@arm.com,
	xen-devel@lists.xenproject.org, sstabellini@kernel.org
Subject: Re: [PATCH 05/10] xen/arm: introduce alloc_staticmem_pages
Date: Tue, 18 May 2021 11:09:54 +0100	[thread overview]
Message-ID: <7f36351e-fa08-ea74-cbc2-049ced7aac4e@xen.org> (raw)
In-Reply-To: <a890200d-b75b-dd59-5d13-b0b211a58da5@suse.com>

Hi Jan,

On 18/05/2021 08:24, Jan Beulich wrote:
> On 18.05.2021 07:21, Penny Zheng wrote:
>> +         * to PGC_state_inuse.
>> +         */
>> +        pg[i].count_info = (pg[i].count_info & PGC_reserved) | PGC_state_inuse;
>> +        /* Initialise fields which have other uses for free pages. */
>> +        pg[i].u.inuse.type_info = 0;
>> +        page_set_owner(&pg[i], NULL);
>> +
>> +        /*
>> +         * Ensure cache and RAM are consistent for platforms where the
>> +         * guest can control its own visibility of/through the cache.
>> +         */
>> +        flush_page_to_ram(mfn_x(page_to_mfn(&pg[i])),
>> +                            !(memflags & MEMF_no_icache_flush));
>> +    }
>> +
>> +    if ( need_tlbflush )
>> +        filtered_flush_tlb_mask(tlbflush_timestamp);
> 
> With reserved pages dedicated to a specific domain, in how far is it
> possible that stale mappings from a prior use can still be around,
> making such TLB flushing necessary?

I would rather not make the assumption. I can see future where we just 
want to allocate memory from a static pool that may be shared with 
multiple domains.

Cheers,

-- 
Julien Grall