linux-kernel - Re: [RFC, PATCH 00/12] TDX: Enable Dynamic PAMT

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Message-ID: <2a3b9f44-6509-48b5-9453-9f4faba752a4@intel.com>
Date: Thu, 15 May 2025 07:03:32 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Zhi Wang <zhiw@...dia.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, rick.p.edgecombe@...el.com,
 isaku.yamahata@...el.com, kai.huang@...el.com, yan.y.zhao@...el.com,
 tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, kvm@...r.kernel.org, x86@...nel.org,
 linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [RFC, PATCH 00/12] TDX: Enable Dynamic PAMT

On 5/15/25 02:17, Kirill A. Shutemov wrote:
> I don't think we can justify any batching here.

The is one primary goal here:

	Reduce TDX overhead when not running TDX guests.

It has the side-effect of being _able_ to reduce the amount of memory
that TDX guests use when using >=2M pages only. It has the theoretical
capability to do the same for 4k users but only when the pages are quite
contiguous.

Right?

The "not running TDX guest" and ">=2M pages" benefits are relatively
easy. The 4k one is hard and is going to take a lot more work.

Could we please focus on the easy one for now and not get distracted by
the hard one that might not even be worth it in the end?