linux-kernel - Re: [RFC PATCH v2 10/23] KVM: TDX: Enable huge page splitting under write kvm->mmu

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Message-ID: <aTjD5FPl1+ktsRkJ@yzhao56-desk.sh.intel.com>
Date: Wed, 10 Dec 2025 08:50:44 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Sagi Shahar <sagis@...gle.com>
CC: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>, "kvm@...r.kernel.org"
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Subject: Re: [RFC PATCH v2 10/23] KVM: TDX: Enable huge page splitting under
 write kvm->mmu_lock

On Tue, Dec 09, 2025 at 06:28:56PM -0600, Sagi Shahar wrote:
> On Tue, Dec 9, 2025 at 5:54 PM Edgecombe, Rick P
> <rick.p.edgecombe@...el.com> wrote:
> >
> > On Tue, 2025-12-09 at 17:49 -0600, Sagi Shahar wrote:
> > > I was trying to test this code locally (without the DPAMT patches and
> > > with DPAMT disabled) and saw that sometimes tdh_mem_page_demote
> > > returns TDX_INTERRUPTED_RESTARTABLE. Looking at the TDX module code
> > > (version 1.5.16 from [1]) I see that demote and promote are the only
> > > seamcalls that return TDX_INTERRUPTED_RESTARTABLE so it wasn't handled
> > > by KVM until now.
> >
> > Did you see "Open 3" in the coverletter?
> 
> I tested the code using TDX module 1.5.24 which is the latest one we
> got. Is there a newer TDX module that supports this new functionality?
AFAIK, TDX module 1.5.28 is the earliest version that enumerates
TDX_FEATURES0.ENHANCED_DEMOTE_INTERRUPTIBILITY (bit 51) and disables
TDX_INTERRUPTED_RESTARTABLE when there're no L2 TDs. (Please check the
discussions at [1]).

Looks 1.5.28.04 was just released (internally?), with release note saying
"Ensure TDH.MEM.PAGE.DEMOTE forward progress for non partitioned TDs".

Not sure if you can check it.

[1] https://lore.kernel.org/all/aRRAFhw11Dwcw7RG@yzhao56-desk.sh.intel.com/