linux-kernel - Re: [RFC PATCH 08/21] KVM: TDX: Increase/decrease folio ref for huge pages

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Message-ID: <aHb/ETOMSQRm1bMO@yzhao56-desk>
Date: Wed, 16 Jul 2025 09:23:29 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Ackerley Tng <ackerleytng@...gle.com>
CC: <vannapurve@...gle.com>, <pbonzini@...hat.com>, <seanjc@...gle.com>,
	<linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>, <x86@...nel.org>,
	<rick.p.edgecombe@...el.com>, <dave.hansen@...el.com>,
	<kirill.shutemov@...el.com>, <tabba@...gle.com>, <quic_eberman@...cinc.com>,
	<michael.roth@....com>, <david@...hat.com>, <vbabka@...e.cz>,
	<jroedel@...e.de>, <thomas.lendacky@....com>, <pgonda@...gle.com>,
	<zhiquan1.li@...el.com>, <fan.du@...el.com>, <jun.miao@...el.com>,
	<ira.weiny@...el.com>, <isaku.yamahata@...el.com>, <xiaoyao.li@...el.com>,
	<binbin.wu@...ux.intel.com>, <chao.p.peng@...el.com>
Subject: Re: [RFC PATCH 08/21] KVM: TDX: Increase/decrease folio ref for huge
 pages

On Thu, Jun 05, 2025 at 03:35:50PM -0700, Ackerley Tng wrote:
> Yan Zhao <yan.y.zhao@...el.com> writes:
> 
> > On Wed, Jun 04, 2025 at 01:02:54PM -0700, Ackerley Tng wrote:
> >> Hi Yan,
> >> 
> >> While working on the 1G (aka HugeTLB) page support for guest_memfd
> >> series [1], we took into account conversion failures too. The steps are
> >> in kvm_gmem_convert_range(). (It might be easier to pull the entire
> >> series from GitHub [2] because the steps for conversion changed in two
> >> separate patches.)
> > ...
> >> [2] https://github.com/googleprodkernel/linux-cc/tree/gmem-1g-page-support-rfc-v2
> >
> > Hi Ackerley,
> > Thanks for providing this branch.
> 
> Here's the WIP branch [1], which I initially wasn't intending to make
> super public since it's not even RFC standard yet and I didn't want to
> add to the many guest_memfd in-flight series, but since you referred to
> it, [2] is a v2 of the WIP branch :)
> 
> [1] https://github.com/googleprodkernel/linux-cc/commits/wip-tdx-gmem-conversions-hugetlb-2mept
> [2] https://github.com/googleprodkernel/linux-cc/commits/wip-tdx-gmem-conversions-hugetlb-2mept-v2
Hi Ackerley,

I'm working on preparing TDX huge page v2 based on [2] from you. The current
decision is that the code base of TDX huge page v2 needs to include DPAMT
and VM shutdown optimization as well.

So, we think kvm-x86/next is a good candidate for us.
(It is in repo https://github.com/kvm-x86/linux.git
 commit 87198fb0208a (tag: kvm-x86-next-2025.07.15, kvm-x86/next) Merge branch 'vmx',
 which already includes code for VM shutdown optimization).
I still need to port DPAMT + gmem 1G + TDX huge page v2 on top it.

Therefore, I'm wondering if the rebase of [2] onto kvm-x86/next can be done
from your side. A straightforward rebase is sufficient, with no need for
any code modification. And it's better to be completed by the end of next
week.

We thought it might be easier for you to do that (but depending on your
bandwidth), allowing me to work on the DPAMT part for TDX huge page v2 in
parallel.

However, if it's difficult for you, please feel free to let us know.

Thanks
Yan