From nobody Tue Dec 16 14:43:32 2025 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (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 9D661375744 for ; Thu, 30 Oct 2025 20:10:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761855009; cv=none; b=kkxHdYS5M3sA2Xkt2z76XJ6lQawHbVUtN7rMQBRfml0yot/vqVnL6kwsr4PzvJ8rN3Aj6RRHWDcUJmJWLU/QDTjLyazMTH89xqT6ubacfoXVgvCxft0v9JeK6zPD/Af0RD0lsUfXoDQnS9msYBlx7GeZZCdseDYNjMg4+zXwtbw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761855009; c=relaxed/simple; bh=MUDH20eIOuOTsz0KS9uuqL90AQHBBTqkmMlPBeDR0dg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=T//l0+40z6HovReWtdOH5YU2w1NekZU6V7l25VdocAAvpMMZV3S/Eb/Av8lP+ICdMHCndY8hPzuRPzHMGcq4TXC/3q4yrZ9SvzUWpI+GxYTRfc0QaAFKYHCg9LcxcIIG3vFlLBNHUAHBAX3n39zxP2bGmsXNMONPlm4mID/SL/8= 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=T5UwO06f; arc=none smtp.client-ip=209.85.215.202 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="T5UwO06f" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-b63038a6350so1675643a12.0 for ; Thu, 30 Oct 2025 13:10:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1761855007; x=1762459807; darn=vger.kernel.org; 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=TnV5Uo4WEDSyHqNRydChmPWwv04NNnacTlgMSv81cvQ=; b=T5UwO06f5YYUjTOoIBnQeZqZF3MXwA1xsiU1nObbLP4/tgmhojQYA0acKw+ROJdLk9 /nhe7veeJ9PR6/EvlxZ/mL4TOA/L5gZn2S0eczabNl9X2qMRy0wrgO17HvSvr3Cnmvoe Ebc3mpQ1/R4HhJ6Zhp2PBi/Bd3WEzUf1WjQ3zT3PF0qlQ6BlaQNN4B85rknkW0/4a65U TTQwXCjGC76CGEUdnqoTejpjoQ9+G3P1mTGkf9++df2k+gUwVdj4UiZX9JuhsIO7wCRo czlCTLXHHsmRVXv6UnoyWtnqqCcU8z0eJERJy4epx5L577EKtT42wHUbSYvVKx0YiY6Z NSpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761855007; x=1762459807; 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=TnV5Uo4WEDSyHqNRydChmPWwv04NNnacTlgMSv81cvQ=; b=ubj0WVzUNeFvJ3353Qxjn/YoZsihylAhyPu0Y3nuHfHo3AllkOWBPWnugtvajwfnqW WdxT2AK1DlOscI1x+OC6bVzmjaNqJSRGfo3uIre8FJrJT2I3j/7pg1+MqpWo1tPK2vFi YHPBB4K9vNa2biTc6spA9oTynjdVUpQ5iTBMS/d1Hburfb2bAQnWOtSA7kUYPK90HibV hQ43kE4hfu/bef7rOl3vHAt+KWodbu2MOgg9AauIS6QlZB9XFsda6EYFQQ1EntWg8fOF 06lSni+FWBc/pfw/0MlM6AYAB+MMGeAL3B2j7MS95+mVPJvzy2EMJ0SeOLsrw9hVtuoC 3qwg== X-Forwarded-Encrypted: i=1; AJvYcCXgIA0i0H7MkibF0ox7pPuxWAUKTA4ELkhidy6oqmHQW6XORgfssBKMhDn+obY3gFGJKAR+sZb6ZpBs6bI=@vger.kernel.org X-Gm-Message-State: AOJu0YxAOg+FbCuRd5m80fORxXdgNAcMN+ksk7gBiyyq6nvBiCw3m5o1 oSofbZ5g4GDg+Kpa3EvLbHsWOvQNGXtftMj4tl1Rt0WgK1E3plfvnO3y5BRoFKFwVcqUyLOoBl8 GpD3P9w== X-Google-Smtp-Source: AGHT+IFGhHo2Di0bU/Eld4A49PARSXoqPeeyu/ySpV1D9gJIOdjNn1G+WqeVqdSQrN5R+YSZ+ehbNpIGVJQ= X-Received: from plow8.prod.google.com ([2002:a17:903:1b08:b0:267:cd3d:3446]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:f54c:b0:295:134:9ae5 with SMTP id d9443c01a7336-29519b9f27cmr11657375ad.24.1761855006488; Thu, 30 Oct 2025 13:10:06 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 30 Oct 2025 13:09:26 -0700 In-Reply-To: <20251030200951.3402865-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251030200951.3402865-1-seanjc@google.com> X-Mailer: git-send-email 2.51.1.930.gacf6e81ea2-goog Message-ID: <20251030200951.3402865-4-seanjc@google.com> Subject: [PATCH v4 03/28] KVM: TDX: Drop PROVE_MMU=y sanity check on to-be-populated mappings 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 , Binbin Wu , Michael Roth , Yan Zhao , Vishal Annapurve , Rick Edgecombe , Ackerley Tng Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Drop TDX's sanity check that a mirror EPT mapping isn't zapped between creating said mapping and doing TDH.MEM.PAGE.ADD, as the check is simultaneously superfluous and incomplete. Per commit 2608f1057601 ("KVM: x86/tdp_mmu: Add a helper function to walk down the TDP MMU"), the justification for introducing kvm_tdp_mmu_gpa_is_mapped() was to check that the target gfn was pre-populated, with a link that points to this snippet: : > One small question: : > : > What if the memory region passed to KVM_TDX_INIT_MEM_REGION hasn't bee= n pre- : > populated? If we want to make KVM_TDX_INIT_MEM_REGION work with these= regions, : > then we still need to do the real map. Or we can make KVM_TDX_INIT_ME= M_REGION : > return error when it finds the region hasn't been pre-populated? : : Return an error. I don't love the idea of bleeding so many TDX details = into : userspace, but I'm pretty sure that ship sailed a long, long time ago. But that justification makes little sense for the final code, as the check on nr_premapped after TDH.MEM.PAGE.ADD will detect and return an error if KVM attempted to zap a S-EPT entry (tdx_sept_zap_private_spte() will fail on TDH.MEM.RANGE.BLOCK due lack of a valid S-EPT entry). And as evidenced by the "is mapped?" code being guarded with CONFIG_KVM_PROVE_MMU=3Dy, KVM is NOT relying on the check for general correctness. The sanity check is also incomplete in the sense that mmu_lock is dropped between the check and TDH.MEM.PAGE.ADD, i.e. will only detect KVM bugs that zap SPTEs in a very specific window (note, this also applies to the check on nr_premapped). Removing the sanity check will allow removing kvm_tdp_mmu_gpa_is_mapped(), which has no business being exposed to vendor code, and more importantly will pave the way for eliminating the "pre-map" approach entirely in favor of doing TDH.MEM.PAGE.ADD under mmu_lock. Reviewed-by: Ira Weiny Reviewed-by: Kai Huang Reviewed-by: Binbin Wu Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/tdx.c | 14 -------------- 1 file changed, 14 deletions(-) diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 326db9b9c567..4c3014befe9f 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3181,20 +3181,6 @@ static int tdx_gmem_post_populate(struct kvm *kvm, g= fn_t gfn, kvm_pfn_t pfn, if (ret < 0) goto out; =20 - /* - * The private mem cannot be zapped after kvm_tdp_map_page() - * because all paths are covered by slots_lock and the - * filemap invalidate lock. Check that they are indeed enough. - */ - if (IS_ENABLED(CONFIG_KVM_PROVE_MMU)) { - scoped_guard(read_lock, &kvm->mmu_lock) { - if (KVM_BUG_ON(!kvm_tdp_mmu_gpa_is_mapped(vcpu, gpa), kvm)) { - ret =3D -EIO; - goto out; - } - } - } - ret =3D 0; err =3D tdh_mem_page_add(&kvm_tdx->td, gpa, pfn_to_page(pfn), src_page, &entry, &level_state); --=20 2.51.1.930.gacf6e81ea2-goog