linux-kernel - Re: [PATCH v4 07/16] x86/virt/tdx: Add tdx_alloc/free

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Message-ID: <e0eb7ab13b715c7509a310bbc043f78898002442.camel@intel.com>
Date: Wed, 3 Dec 2025 21:39:07 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "Hansen, Dave" <dave.hansen@...el.com>, "nik.borisov@...e.com"
	<nik.borisov@...e.com>, "kas@...nel.org" <kas@...nel.org>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "Li, Xiaoyao"
	<xiaoyao.li@...el.com>, "Huang, Kai" <kai.huang@...el.com>,
	"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>, "Zhao, Yan Y"
	<yan.y.zhao@...el.com>, "Wu, Binbin" <binbin.wu@...el.com>,
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Subject: Re: [PATCH v4 07/16] x86/virt/tdx: Add tdx_alloc/free_page() helpers

On Wed, 2025-12-03 at 12:13 -0800, Dave Hansen wrote:
> BTW, I *DO* expect the DPAMT pages to be mostly allocated forever. Maybe
> I'm just a pessimist, but you can't get them back for compaction or
> reclaim, so they're basically untouchable. Sure, if you kill all the TDX
> guests you get them back, but that's a very different kind of kernel
> memory from stuff that's truly reclaimable under pressure.

If we want to improve it (later) we could topup via a single higher order
allocation. So like if we need 15 pages we could round up to an order-4, then
hand them out individually. But I suspect someone would want to see some proof
before that kind of tweak.

So I take it you are ok to leave the general approach, but worth trying to
remove the dynamic sizing.