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AJvYcCX0iQR0KecUQtO8+TIpzjz3r6BI9AmPYJs24c6OwWBppaBzeLWmORtWsT2aroiqcTh3zbyFLmC0B1BcLrM=@vger.kernel.org X-Gm-Message-State: AOJu0YyjybTj9qYEUsOgUw1a5S3NRa0oXf0lpNI1NxzjuOG7cdge9l30 QhPrukzU5Vf5Xlr/efWxSjh//brqk2/P1o+Nb5U9HNfLikDu+3AvuLr58L2lIpwqSFsol3gys74 8tFinzA== X-Google-Smtp-Source: AGHT+IEf2CEnlJGHZtsmzrHqeOd1ndTjoACnl8CdMuKToTrbMjiAb+CrTNoHK0d+D+dNU6wwE2PLQDR3nAM= X-Received: from pjbsk5.prod.google.com ([2002:a17:90b:2dc5:b0:325:9cb3:419e]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:3c45:b0:327:b824:2257 with SMTP id 98e67ed59e1d1-327b8242bbemr4417101a91.32.1756426000789; Thu, 28 Aug 2025 17:06:40 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 28 Aug 2025 17:06:11 -0700 In-Reply-To: <20250829000618.351013-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250829000618.351013-1-seanjc@google.com> X-Mailer: git-send-email 2.51.0.318.gd7df087d1a-goog Message-ID: <20250829000618.351013-12-seanjc@google.com> Subject: [RFC PATCH v2 11/18] KVM: TDX: Fold tdx_mem_page_record_premap_cnt() into its sole caller From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Ira Weiny , Kai Huang , Michael Roth , Yan Zhao , Vishal Annapurve , Rick Edgecombe , Ackerley Tng Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Signed-off-by: Sean Christopherson Reviewed-by: Rick Edgecombe --- arch/x86/kvm/vmx/tdx.c | 49 ++++++++++++++++++------------------------ 1 file changed, 21 insertions(+), 28 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index fe0815d542e3..06dd2861eba7 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1608,29 +1608,6 @@ static int tdx_mem_page_aug(struct kvm *kvm, gfn_t g= fn, return 0; } =20 -/* - * KVM_TDX_INIT_MEM_REGION calls kvm_gmem_populate() to map guest pages; t= he - * callback tdx_gmem_post_populate() then maps pages into private memory. - * through the a seamcall TDH.MEM.PAGE.ADD(). The SEAMCALL also requires = the - * private EPT structures for the page to have been built before, which is - * done via kvm_tdp_map_page(). nr_premapped counts the number of pages th= at - * were added to the EPT structures but not added with TDH.MEM.PAGE.ADD(). - * The counter has to be zero on KVM_TDX_FINALIZE_VM, to ensure that there - * are no half-initialized shared EPT pages. - */ -static int tdx_mem_page_record_premap_cnt(struct kvm *kvm, gfn_t gfn, - enum pg_level level, kvm_pfn_t pfn) -{ - struct kvm_tdx *kvm_tdx =3D to_kvm_tdx(kvm); - - if (KVM_BUG_ON(kvm->arch.pre_fault_allowed, kvm)) - return -EIO; - - /* nr_premapped will be decreased when tdh_mem_page_add() is called. */ - atomic64_inc(&kvm_tdx->nr_premapped); - return 0; -} - static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, enum pg_level level, kvm_pfn_t pfn) { @@ -1641,14 +1618,30 @@ static int tdx_sept_set_private_spte(struct kvm *kv= m, gfn_t gfn, return -EIO; =20 /* - * Read 'pre_fault_allowed' before 'kvm_tdx->state'; see matching - * barrier in tdx_td_finalize(). + * Ensure pre_fault_allowed is read by kvm_arch_vcpu_pre_fault_memory() + * before kvm_tdx->state. Userspace must not be allowed to pre-fault + * arbitrary memory until the initial memory image is finalized. Pairs + * with the smp_wmb() in tdx_td_finalize(). */ smp_rmb(); - if (likely(kvm_tdx->state =3D=3D TD_STATE_RUNNABLE)) - return tdx_mem_page_aug(kvm, gfn, level, pfn); =20 - return tdx_mem_page_record_premap_cnt(kvm, gfn, level, pfn); + /* + * 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 + * have been added to the image, to prevent running the TD with a + * valid mapping in the mirror EPT, but not in the S-EPT. + */ + if (unlikely(kvm_tdx->state !=3D TD_STATE_RUNNABLE)) { + if (KVM_BUG_ON(kvm->arch.pre_fault_allowed, kvm)) + return -EIO; + + atomic64_inc(&kvm_tdx->nr_premapped); + return 0; + } + + return tdx_mem_page_aug(kvm, gfn, level, pfn); } =20 static int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn, --=20 2.51.0.318.gd7df087d1a-goog