Re: [PATCH v2 5/5] xen/memory, tools: Make init-dom0less consume XEN_DOMCTL_get_mem_map

From: Henry Wang <xin.wang2@amd.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: Wei Liu <wl@xen.org>, Anthony PERARD <anthony.perard@citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	George Dunlap <george.dunlap@citrix.com>,
	Julien Grall <julien@xen.org>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Alec Kwapis <alec.kwapis@medtronic.com>,
	<xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v2 5/5] xen/memory, tools: Make init-dom0less consume XEN_DOMCTL_get_mem_map
Date: Tue, 12 Mar 2024 15:36:42 +0800	[thread overview]
Message-ID: <8a4da09f-b880-46f5-a2ad-b29b77f39108@amd.com> (raw)
In-Reply-To: <7b9f3e46-8a70-403f-a98c-e53bea04b389@suse.com>

Hi Jan,

On 3/12/2024 3:34 PM, Jan Beulich wrote:
> On 12.03.2024 04:44, Henry Wang wrote:
>> On 3/12/2024 1:07 AM, Jan Beulich wrote:
>>> On 08.03.2024 02:54, Henry Wang wrote:
>>>> --- a/xen/include/public/memory.h
>>>> +++ b/xen/include/public/memory.h
>>>> @@ -41,6 +41,11 @@
>>>>    #define XENMEMF_exact_node(n) (XENMEMF_node(n) | XENMEMF_exact_node_request)
>>>>    /* Flag to indicate the node specified is virtual node */
>>>>    #define XENMEMF_vnode  (1<<18)
>>>> +/*
>>>> + * Flag to force populate physmap to use pages from domheap instead of 1:1
>>>> + * or static allocation.
>>>> + */
>>>> +#define XENMEMF_force_heap_alloc  (1<<19)
>>>>    #endif
>>> If this is for populate_physmap only, then other sub-ops need to reject
>>> its use.
>>>
>>> I have to admit I'm a little wary of allocating another flag here and ...
>>>
>>>> --- a/xen/include/xen/mm.h
>>>> +++ b/xen/include/xen/mm.h
>>>> @@ -205,6 +205,8 @@ struct npfec {
>>>>    #define  MEMF_no_icache_flush (1U<<_MEMF_no_icache_flush)
>>>>    #define _MEMF_no_scrub    8
>>>>    #define  MEMF_no_scrub    (1U<<_MEMF_no_scrub)
>>>> +#define _MEMF_force_heap_alloc 9
>>>> +#define  MEMF_force_heap_alloc (1U<<_MEMF_force_heap_alloc)
>>>>    #define _MEMF_node        16
>>>>    #define  MEMF_node_mask   ((1U << (8 * sizeof(nodeid_t))) - 1)
>>>>    #define  MEMF_node(n)     ((((n) + 1) & MEMF_node_mask) << _MEMF_node)
>>> ... here - we don't have that many left. Since other sub-ops aren't
>>> intended to support this flag, did you consider adding another (perhaps
>>> even arch-specific) sub-op instead?
>> Not really, I basically followed the discussion from [1] to implement
>> this patch. However I understand your concern. Just want to make sure if
>> I understand your suggestion correctly, by "adding another sub-op" you
>> mean adding a sub-op similar as "XENMEM_populate_physmap" but only with
>> executing the "else" part I want, so we can drop the use of these two
>> added flags? Thanks!
>>
>> [1]
>> https://lore.kernel.org/xen-devel/3982ba47-6709-47e3-a9c2-e2d3b4a2d8e3@xen.org/
> In which case please check with Julien (and perhaps other Arm maintainers)
> before deciding on whether to go this alternative route.

Yes sure, I will wait a bit longer for the agreement of the discussion 
before implementing the code.

Kind regards,
Henry

> Jan