From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f227.google.com (mail-pl1-f227.google.com [209.85.214.227]) (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 5238719A288 for ; Tue, 29 Sep 2026 04:03:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.227 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790654605; cv=none; b=ADZnOtOnlVVxs+GNVFi/5B6uu1ms5dmPgUrYcOKSfQgAzMFhs4bdCT28itrMXnUD02PXwG6scsAwQ42FFoUUCHiGYjUWmOEqRgM+x4svqDId8eE0WqDpIcqOKem76aqoAS6fvCu8MGMr9mdyvU59Y7A+4PjjgutN7pyJiLgdgN0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790654605; c=relaxed/simple; bh=cAPVcgsAJorVkgcgjx8qJ2Cz7pTUEIJBuCCMwyGBvoc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nvmZNjKANf0tF2APTY6CWEIraKm8VLDtnDQhykqssHyRuIhxC/Bhy+/LGbnBoddjEDzF0EghY0n+mBKf/QGw+5C7P0/C/YaX8ROjW9NJ/MFUaMCoFCKn12GuE/xoUb+gYoSj/N3LDG7ap+gCJjpMS4RNUTPdMBLomy7PXaP/4+8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=broadcom.com; spf=fail smtp.mailfrom=broadcom.com; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b=S5hD9btE; arc=none smtp.client-ip=209.85.214.227 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=broadcom.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=broadcom.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b="S5hD9btE" Received: by mail-pl1-f227.google.com with SMTP id d9443c01a7336-2e2c837fa12so715735ad.1 for ; Mon, 28 Sep 2026 21:03:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790654603; x=1791259403; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:dkim-signature:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=p1CKCrpax+qcHAbV5I37hg3uq7X1UIkb9ImgfW4E7N8=; b=PlPPiKpfb3FDQUgSCvVV3UB7jLQjzaZo/eo5sl0nQQTO+0+zVFyRocB4g/jnJaonco LKKrrA6/9TZiJJvr5rx9efBjuJYGd3qpmGsUyStS2O0nzKxf7Gl7ivmoY5VmQ+M20iQu e3KoU/M7ZiBZGtRGASrdX7lojRWWSN94MTeTWqZO9RsIPtMR0EyrViXYhACzyloo1hoa ZOeb1egWdKmcgrarwzvRt9PItwSkgK7OmFBGpG4Gy+k2YQWxxtM64PndJtiSA51jUJDA UZfsvmEX9JQh32Vmv4AjCIJ5G6Fd67uFT+z9p/3p9xD8HHIG6FojA5mSoIsOmJTrRpSO 82hw== X-Forwarded-Encrypted: i=1; AKwUvByuhxr9wsebcGhxNDcvSo0DAuhFhnRJDvsgPcDVfCOyUD8cYe3TSj1KokmCL2OREQX3W84=@vger.kernel.org X-Gm-Message-State: AFq9FYLSY2jgwpjZGo13rzxVU2adAfDnn9IA4j9qRpCeU53tI8NcHBEo O958Nal21RhD3/YvZWArnZ6hgT8SbBHliVdIlexA8uPsL8/Du/ntZJt8TSYbpZ/9NHnmLCuZckJ YHUlUzURLhGeVToYSPxHzmCIhbtVDya14l6GAMlY9Ifg5XzA/JTqCgaZQl7eLC9sCCVeT+Ri8Qn a5jUvCtconKk1A7/L5gMlc96tDI2O+dLy9U0JbLjqmnpi91Wm2c1GtqADMXSEKnBKZdbn/JHnjn J9m X-Gm-Gg: AYBFou3IXcMfaqwl8FW64Zc1auZx+hKQOwHm420L0d9/hN5UUD7KE60Xv3KJMtG9WNo enSXFnXrey0SMWIlChYrOinQEcDXSkQDVWJro90FS5bA2NxeVo+fxkB2MZ9vij033HgRIvyCODO FelAM6txKygsTmqR9FlTfrLf9CNLRuaVDWcR8EBs6/IBY61I5dkLMbVW+TjM5LSt2oL1IHda6Fl GTqDHrqsdQjAsw6dNBPIMzyIE8O0Gdt34R+v37TYV6V7eUgQ9xINuPFC4rQVms2luQKl/QIrRcU QKYjvwtXgtr1hpxz5pUd4fjeUSaL5vU3L0pkY8g+9SkkoT2GyrS8DVlWbUjKHX14eKKHARqvbWX dIDNxexgCZOgtRRU431eVSXdwjBxgUnDYVptbHn6Bhi7Sz6SuMppRTEh2SlApxj7oEYRRLxwWRZ 6Bj1LmDH+cxVhj9jlqHCV3o2Y4kg3ss2/F X-Received: by 2002:a17:90b:390d:b0:3a0:c717:2db with SMTP id 98e67ed59e1d1-3a0c7170934mr6606637a91.27.1790654603435; Mon, 28 Sep 2026 21:03:23 -0700 (PDT) Received: from smtp-us-east1-p01-i01-si01.dlp.protect.broadcom.com (address-144-49-247-18.dlp.protect.broadcom.com. [144.49.247.18]) by smtp-relay.gmail.com with ESMTPS id 98e67ed59e1d1-3a497e9ab17sm1002106a91.3.2026.09.28.21.03.22 for (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Sep 2026 21:03:23 -0700 (PDT) X-Relaying-Domain: broadcom.com X-CFilter-Loop: Reflected Received: by mail-dy1-f197.google.com with SMTP id 5a478bee46e88-33713e5e6daso5804016eec.0 for ; Mon, 28 Sep 2026 21:03:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; t=1790654601; x=1791259401; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=p1CKCrpax+qcHAbV5I37hg3uq7X1UIkb9ImgfW4E7N8=; b=S5hD9btEeeCasujz5w9QZDPjqqKKIrEHlJMVqOqhX8KtIl+hs1yg3FyozSXIHCQDtD 9u57WciCTYugRIfLEGeT5e2xFFu67Xc8zbGGVunTFXU+nSERWicaZLT2ywSoRAPCSJWn 5zgf3Rs94gkb08ZDMg2/ffnuONLXuLnDyT+jE= X-Forwarded-Encrypted: i=1; AKwUvByaqWaAvRA+9Sik07CIBKyud5p6eQDnVLYh/YTtPcYDJoG/aboYYny/OV6kTEq9fbDbO1Q=@vger.kernel.org X-Received: by 2002:a05:693c:4099:b0:34b:401a:4648 with SMTP id 5a478bee46e88-34b40298aa6mr875187eec.20.1790654601402; Mon, 28 Sep 2026 21:03:21 -0700 (PDT) X-Received: by 2002:a05:693c:4099:b0:34b:401a:4648 with SMTP id 5a478bee46e88-34b40298aa6mr875122eec.20.1790654600700; Mon, 28 Sep 2026 21:03:20 -0700 (PDT) Received: from vertex.localdomain ([192.19.144.250]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-347323f5a7esm10952571eec.15.2026.09.28.21.03.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Sep 2026 21:03:18 -0700 (PDT) From: Zack Rusin To: Kiryl Shutsemau , Borislav Petkov , x86@kernel.org, Dennis Zhou , Tejun Heo , Arnd Bergmann , Rick Edgecombe , Tom Lendacky , Wei Liu , Dexuan Cui , Paolo Bonzini , Vitaly Kuznetsov Cc: Ajay Kaher , Alexey Makhalov , Thomas Gleixner , Ingo Molnar , Dave Hansen , "H. Peter Anvin" , virtualization@lists.linux.dev, bcm-kernel-feedback-list@broadcom.com, linux-kernel@vger.kernel.org, Christoph Lameter , Andrew Morton , Bo Gan , linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org, Jonathan Corbet , "K. Y. Srinivasan" , Haiyang Zhang , Long Li , Andy Lutomirski , Peter Zijlstra , linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, Nathan Chancellor , Kees Cook , Ashish Kalra Subject: [PATCH v2 3/6] x86/percpu: Require embedded allocation in encrypted guests Date: Tue, 29 Sep 2026 00:02:52 -0400 Message-ID: <20260929040256.543767-4-zack.rusin@broadcom.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260929040256.543767-1-zack.rusin@broadcom.com> References: <20260929040256.543767-1-zack.rusin@broadcom.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e Early sharing needs direct-mapped per-CPU storage. In TDX, a private direct-map alias of a shared page can terminate the guest, including through load_unaligned_zeropad(). Require embed rather than adding early vmalloc conversion and alias synchronization. Warn when overriding percpu_alloc=page and let embed failures reach the existing panic. Restrict this policy to encrypted guests, leaving host SME allocation unchanged. Suggested-by: Kiryl Shutsemau Link: https://lore.kernel.org/r/aqvxQoIoYhJTZpAC@thinkstation Signed-off-by: Zack Rusin --- Documentation/admin-guide/kernel-parameters.txt | 3 +++ arch/x86/kernel/setup_percpu.c | 12 ++++++++++-- 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 33cd30996e47..8ba881af3520 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5347,6 +5347,9 @@ Kernel parameters See comments in mm/percpu.c for details on each allocator. This parameter is primarily for debugging and performance comparison. + On x86 encrypted guests, only "embed" is supported; + "page" is ignored with a warning. An embed allocation + failure is fatal instead of falling back to "page". pirq= [SMP,APIC] Manual mp-table setup See Documentation/arch/x86/i386/IO-APIC.rst. diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c index bfa48e7a32a2..c83c61e0b20a 100644 --- a/arch/x86/kernel/setup_percpu.c +++ b/arch/x86/kernel/setup_percpu.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include #include @@ -112,6 +113,7 @@ void __init setup_per_cpu_areas(void) { unsigned int cpu; unsigned long delta; + bool encrypted = cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT); int rc; pr_info("NR_CPUS:%d nr_cpumask_bits:%d nr_cpu_ids:%u nr_node_ids:%u\n", @@ -127,6 +129,12 @@ void __init setup_per_cpu_areas(void) if (pcpu_chosen_fc == PCPU_FC_AUTO && pcpu_need_numa()) pcpu_chosen_fc = PCPU_FC_PAGE; #endif + if (encrypted) { + if (pcpu_chosen_fc == PCPU_FC_PAGE) + pr_warn("Ignoring percpu_alloc=page in an encrypted guest\n"); + pcpu_chosen_fc = PCPU_FC_EMBED; + } + rc = -EINVAL; if (pcpu_chosen_fc != PCPU_FC_PAGE) { const size_t dyn_size = PERCPU_MODULE_RESERVE + @@ -149,11 +157,11 @@ void __init setup_per_cpu_areas(void) dyn_size, atom_size, pcpu_cpu_distance, pcpu_cpu_to_node); - if (rc < 0) + if (rc < 0 && !encrypted) pr_warn("%s allocator failed (%d), falling back to page size\n", pcpu_fc_names[pcpu_chosen_fc], rc); } - if (rc < 0) + if (rc < 0 && !encrypted) rc = pcpu_page_first_chunk(PERCPU_FIRST_CHUNK_RESERVE, pcpu_cpu_to_node); if (rc < 0) -- 2.53.0