From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 11D592877C2 for ; Fri, 17 Oct 2025 00:33:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760661194; cv=none; b=gBYFMBWsy4VWtx0Z3yiy6e58TL+7nw7zObdyiXtoGlcQ/OPkp57LoZrVli7oNktlZnM7CXwdy1fYBZ4jSyHjklPEq53R++Lz9093noHzz52k74IOWP4kP+OW3GfGh53XRhX3zt5bTCn853cAUCMSMkkP1x59IP/dO+PCckhJY20= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760661194; c=relaxed/simple; bh=g9XE/XmOjyDDyTFp1eZETSR7kpDfFGyQ7oUmnFxVe5U=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=i8OcC2+YvrFCuOC572sIvDy1CIW4RwpLUzqiyHfxX5hHizYdGZ9rF5mFm9Dl+R5DzEjt2fOFrZEtu/nv6yCyzdu5e2dvpKhVpUOzfaL+kjufjbTASePOx2P4ucmOBrw8ZRlJmwdeSXe2CdAQIa8Fl9rwdzr4KbStJp3TzOXI49c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=4AE8NTRG; arc=none smtp.client-ip=209.85.216.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="4AE8NTRG" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-32eb18b5500so2174539a91.2 for ; Thu, 16 Oct 2025 17:33:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1760661191; x=1761265991; darn=lists.linux.dev; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=tdDvnnMBi79Itp61RxW2nV56QIHnitcyrtTO64NTOt8=; b=4AE8NTRGrqjQBBl5S0EhLHNt8PM7/kjAIff0b0iCJRXmsRRNBm6w8aHuXlYGgKxy3q y7MvkNXU5AMGsADgiwdnxd2MdEFHT35leK94+anlkfTjNc+xvqoyAf78oG1o4mt3OzLq 7Qc5isIHdv1i8kcSr72VfxeM0IFo0xlGz4a44yB/XN7UsQnbQ/WWnrgaczyhgQ3xq60f 6r8JZrvhEjFYlq6t0N317CEzldkoI+dpaMTJ85GB4b+PZKBd2m/tJ0P42x3PJau9gBrU aTmiJrF/tdI37VKQXz6yaVwsKxKrkKnPbDQxPNR3pIyoajNy8geKz5wHJoDSeYEEjgZZ UZfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760661191; x=1761265991; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=tdDvnnMBi79Itp61RxW2nV56QIHnitcyrtTO64NTOt8=; b=nrspVhAUlEPjh72FO1MUaXAP1/XJvpIusHFf/tCe37TWy2/ibTS9YCe2pO2f6G6nL/ 5juyTbl5vau509yff1SnMvKdvd/7z8h/zY4groYRIoruFiKYf7wKCUsXdp0xRw7pksY7 /XDCYDDRD3d2koKrJ3KXzPVPhXFwiAXXWEsr7YGdf4I8Ej97gMnMh5tl0SY+5GShPSvl C8TOIuF2O8pd4a/+1uAcAA+hsFOTZtwv8XHLfKQH+4wPubrcff84oP65nEoc11i+D7L/ HYmwECK3Z/UYLEUkvV5qAeXmKqcnyeZKDnMBi4eXDhM4VML3NVZXLT7lc9QQmwubEUNQ dBZg== X-Forwarded-Encrypted: i=1; AJvYcCVuz6D0vPh4rNAScjXQVBq85DLnOCFSsdLz9xpYfaCATrgP0dyoOimH0t2J9K9Oud6OboFgnHwDtoEG@lists.linux.dev X-Gm-Message-State: AOJu0Yxvnlfem5SCBT0b3u/OjnPcXOU/EOQqmaTHtWrGvVfhALquB6fZ 1Ct56SaY/5v6dRL09w/pV4TUjrvKIPIRvNDWgj0SJoyzcrRCsJpjMjdhqhlmRI4YcnNN/It0Pte rMQoS/Q== X-Google-Smtp-Source: AGHT+IFjbvhuJBf5rM9mXEGAaRcwet/6S3ph7hsVNQrCN7ddhA3ec/NJFjzeh48C6n1kB16/mom5cp7HTgE= X-Received: from pjso17.prod.google.com ([2002:a17:90a:c091:b0:32e:3830:65f2]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:1dc4:b0:330:6f13:53fc with SMTP id 98e67ed59e1d1-33bcf8f870bmr1842078a91.27.1760661191207; Thu, 16 Oct 2025 17:33:11 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 16 Oct 2025 17:32:31 -0700 In-Reply-To: <20251017003244.186495-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251017003244.186495-1-seanjc@google.com> X-Mailer: git-send-email 2.51.0.858.gf9c4a03a3a-goog Message-ID: <20251017003244.186495-14-seanjc@google.com> Subject: [PATCH v3 13/25] KVM: TDX: Fold tdx_mem_page_record_premap_cnt() into its sole caller From: Sean Christopherson To: Marc Zyngier , Oliver Upton , Tianrui Zhao , Bibo Mao , Huacai Chen , Madhavan Srinivasan , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Sean Christopherson , Paolo Bonzini , "Kirill A. Shutemov" Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, x86@kernel.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, Ira Weiny , Kai Huang , Michael Roth , Yan Zhao , Vishal Annapurve , Rick Edgecombe , Ackerley Tng , Binbin Wu 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. Reviewed-by: Rick Edgecombe Signed-off-by: Sean Christopherson --- 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 6c0adc1b3bd5..c37591730cc5 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -1605,29 +1605,6 @@ static int tdx_mem_page_aug(struct kvm *kvm, gfn_t gfn, return 0; } -/* - * KVM_TDX_INIT_MEM_REGION calls kvm_gmem_populate() to map guest pages; the - * 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 that - * 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 = 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) { @@ -1638,14 +1615,30 @@ static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn, return -EIO; /* - * 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 == TD_STATE_RUNNABLE)) - return tdx_mem_page_aug(kvm, gfn, level, pfn); - 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 != 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); } static int tdx_sept_link_private_spt(struct kvm *kvm, gfn_t gfn, -- 2.51.0.858.gf9c4a03a3a-goog