linux-kernel - Re: [PATCH v3 13/25] KVM: TDX: Fold tdx_mem_page_record_premap

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Message-ID: <59ae9957-88a8-4777-9bd2-196e8b4eb8ac@linux.intel.com>
Date: Mon, 27 Oct 2025 17:01:49 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>,
 Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>,
 Huacai Chen <chenhuacai@...nel.org>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>, Anup Patel <anup@...infault.org>,
 Paul Walmsley <pjw@...nel.org>, Palmer Dabbelt <palmer@...belt.com>,
 Albert Ou <aou@...s.berkeley.edu>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Janosch Frank <frankja@...ux.ibm.com>,
 Claudio Imbrenda <imbrenda@...ux.ibm.com>,
 Paolo Bonzini <pbonzini@...hat.com>, "Kirill A. Shutemov" <kas@...nel.org>,
 linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
 kvm@...r.kernel.org, loongarch@...ts.linux.dev, linux-mips@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org,
 linux-riscv@...ts.infradead.org, x86@...nel.org, linux-coco@...ts.linux.dev,
 linux-kernel@...r.kernel.org, Ira Weiny <ira.weiny@...el.com>,
 Kai Huang <kai.huang@...el.com>, Michael Roth <michael.roth@....com>,
 Yan Zhao <yan.y.zhao@...el.com>, Vishal Annapurve <vannapurve@...gle.com>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>,
 Ackerley Tng <ackerleytng@...gle.com>
Subject: Re: [PATCH v3 13/25] KVM: TDX: Fold tdx_mem_page_record_premap_cnt()
 into its sole caller

On 10/25/2025 12:33 AM, Sean Christopherson wrote:
> On Fri, Oct 24, 2025, Binbin Wu wrote:
>>
>> On 10/17/2025 8:32 AM, Sean Christopherson wrote:
>>> Fold tdx_mem_page_record_premap_cnt() into tdx_sept_set_private_spte() as
>>> providing a one-off helper for effectively three lines of code is at best a
>>> wash, and splitting the code makes the comment for smp_rmb()  _extremely_
>>> confusing as the comment talks about reading kvm->arch.pre_fault_allowed
>>> before kvm_tdx->state, but the immediately visible code does the exact
>>> opposite.
>>>
>>> Opportunistically rewrite the comments to more explicitly explain who is
>>> checking what, as well as _why_ the ordering matters.
>>>
>>> No functional change intended.
>>>
>>> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
>>> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
>> Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>
>>
>> One nit below.
>>
>> [...]
>>> +	/*
>>> +	 * If the TD isn't finalized/runnable, then userspace is initializing
>>> +	 * the VM image via KVM_TDX_INIT_MEM_REGION.  Increment the number of
>>> +	 * pages that need to be mapped and initialized via TDH.MEM.PAGE.ADD.
>>> +	 * KVM_TDX_FINALIZE_VM checks the counter to ensure all mapped pages
>>                                                                     ^
>>                                                  Nit: Is pre-mapped better?
> Yeah, updated (and then it gets deleted a few commits later :-) ).
Oh, right, nr_premapped will be dropped later.

Since the whole nr_premapped will be dropped, do we still need a cleanup patch
like patch 12 which will be dropped finally?