From nobody Tue Dec 16 16:41:37 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9FD3DC4167B for ; Thu, 30 Nov 2023 09:39:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229596AbjK3Jj1 (ORCPT ); Thu, 30 Nov 2023 04:39:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42984 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235090AbjK3JjY (ORCPT ); Thu, 30 Nov 2023 04:39:24 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 10255D40; Thu, 30 Nov 2023 01:39:31 -0800 (PST) Date: Thu, 30 Nov 2023 09:39:28 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701337169; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ncQYNJ4GBwdM1wndJD2ZUZuSLFmYqkvecrHz/qccbIw=; b=BCaNQ5C58z8iTkTvRYakAnu/LZz0SLOCLDpBI+oKhATyGp2oWyQmRI/SI7JtNlrzmUWYkE Zrh8NvKRnSjYXXJKwrcqT9xPzK+HiuMHTp4KqLprZlyMzul7XWDX+m8ndudboaYHB774CP 403Zap3yuDiHXtG0PG6ycHTlAx0tcOPXlj35kKkLhfPABQd5K3+tH/IrIH5eqtjDU6NkGf 0Kj1Kz8JsdWfVcjs6RDcl94mpbNvT9pCRoMhpf/bJpP59CRVj1B6APjWon7W8pC1BjBIli 4U0/l+YoK5w44E0SgRWv7t7OCQCHLDvT3qjpqrMtS0RDjIP8Pj+qovCEP2ewJg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701337169; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ncQYNJ4GBwdM1wndJD2ZUZuSLFmYqkvecrHz/qccbIw=; b=lw7uxh9lW6lm5i0CJcL4tB2ETcJ6olfFsuWg+p9gyyr2wUwLk3Y9gSUfGRtHzzr40Gc7YH e8O1M0yenSQQ32Cw== From: "tip-bot2 for Ashwin Dayanand Kamat" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] x86/sev: Fix kernel crash due to late update to read-only ghcb_version Cc: Tom Lendacky , Bo Gan , Ashwin Dayanand Kamat , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <1701254429-18250-1-git-send-email-kashwindayan@vmware.com> References: <1701254429-18250-1-git-send-email-kashwindayan@vmware.com> MIME-Version: 1.0 Message-ID: <170133716855.398.4806769836355142687.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/urgent branch of tip: Commit-ID: 27d25348d42161837be08fc63b04a2559d2e781c Gitweb: https://git.kernel.org/tip/27d25348d42161837be08fc63b04a2559= d2e781c Author: Ashwin Dayanand Kamat AuthorDate: Wed, 29 Nov 2023 16:10:29 +05:30 Committer: Ingo Molnar CommitterDate: Thu, 30 Nov 2023 10:23:12 +01:00 x86/sev: Fix kernel crash due to late update to read-only ghcb_version A write-access violation page fault kernel crash was observed while running cpuhotplug LTP testcases on SEV-ES enabled systems. The crash was observed during hotplug, after the CPU was offlined and the process was migrated to different CPU. setup_ghcb() is called again which tries to update ghcb_version in sev_es_negotiate_protocol(). Ideally this is a read_only variable which is initialised during booting. Trying to write it results in a pagefault: BUG: unable to handle page fault for address: ffffffffba556e70 #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation [ ...] Call Trace: ? __die_body.cold+0x1a/0x1f ? __die+0x2a/0x35 ? page_fault_oops+0x10c/0x270 ? setup_ghcb+0x71/0x100 ? __x86_return_thunk+0x5/0x6 ? search_exception_tables+0x60/0x70 ? __x86_return_thunk+0x5/0x6 ? fixup_exception+0x27/0x320 ? kernelmode_fixup_or_oops+0xa2/0x120 ? __bad_area_nosemaphore+0x16a/0x1b0 ? kernel_exc_vmm_communication+0x60/0xb0 ? bad_area_nosemaphore+0x16/0x20 ? do_kern_addr_fault+0x7a/0x90 ? exc_page_fault+0xbd/0x160 ? asm_exc_page_fault+0x27/0x30 ? setup_ghcb+0x71/0x100 ? setup_ghcb+0xe/0x100 cpu_init_exception_handling+0x1b9/0x1f0 The fix is to call sev_es_negotiate_protocol() only in the BSP boot phase, and it only needs to be done once in any case. [ mingo: Refined the changelog. ] Fixes: 95d33bfaa3e1 ("x86/sev: Register GHCB memory when SEV-SNP is active") Suggested-by: Tom Lendacky Co-developed-by: Bo Gan Signed-off-by: Bo Gan Signed-off-by: Ashwin Dayanand Kamat Signed-off-by: Ingo Molnar Acked-by: Tom Lendacky Link: https://lore.kernel.org/r/1701254429-18250-1-git-send-email-kashwinda= yan@vmware.com --- arch/x86/kernel/sev.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index 70472ee..c672858 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -1234,10 +1234,6 @@ void setup_ghcb(void) if (!cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) return; =20 - /* First make sure the hypervisor talks a supported protocol. */ - if (!sev_es_negotiate_protocol()) - sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ); - /* * Check whether the runtime #VC exception handler is active. It uses * the per-CPU GHCB page which is set up by sev_es_init_vc_handling(). @@ -1255,6 +1251,13 @@ void setup_ghcb(void) } =20 /* + * Make sure the hypervisor talks a supported protocol. + * This gets called only in the BSP boot phase. + */ + if (!sev_es_negotiate_protocol()) + sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ); + + /* * Clear the boot_ghcb. The first exception comes in before the bss * section is cleared. */