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 17417C433FE for ; Fri, 17 Dec 2021 00:13:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229992AbhLQANw (ORCPT ); Thu, 16 Dec 2021 19:13:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229525AbhLQANv (ORCPT ); Thu, 16 Dec 2021 19:13:51 -0500 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 671D6C061574; Thu, 16 Dec 2021 16:13:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=rawG0vRRNmO41OmmJfitNK2c42i0dmNpNba91jNZcAg=; b=j6fid68HKd5sQ2Il9fZeL+XAk2 yo97LdW9pESuCVJdHblgTjCt/ZfOaK5Ok/EgM+JYw03jMjdFXtJBxxb3X/w3FInUSn1OEZPJ8TiI3 Ti9mfYocRv75ciRQqVUj5Onm1VfnGh3b4Mh5ltr1fS9G8Ia32Ardrd96G0dW1o84d7ZwaQL5PJ4PY AxY9xj9/lz341BWJfPyuJublDmWzgGzK4NDTNeISqaITGCqwDINwXUAy7zKlpuBvri1M94FFxku+F tn0t4J49L8i3WOSRxflztLejEi4nGcYGP1LdYUQuZUkND3VtatYlzKmZDHRdOdVw73bPPbNchDEFs 1hfNuAmw==; Received: from [2001:8b0:10b:1::3ae] (helo=u3832b3a9db3152.ant.amazon.com) by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1my0sD-0083Ve-0I; Fri, 17 Dec 2021 00:13:21 +0000 Message-ID: <721484e0fa719e99f9b8f13e67de05033dd7cc86.camel@infradead.org> Subject: Re: [PATCH v3 0/9] Parallel CPU bringup for x86_64 From: David Woodhouse To: Tom Lendacky , Thomas Gleixner Cc: Ingo Molnar , Borislav Petkov , Dave Hansen , "x86@kernel.org" , "H . Peter Anvin" , Paolo Bonzini , "Paul E . McKenney" , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , "rcu@vger.kernel.org" , "mimoja@mimoja.de" , "hewenliang4@huawei.com" , "hushiyuan@huawei.com" , "luolongjun@huawei.com" , "hejingxian@huawei.com" Date: Fri, 17 Dec 2021 00:13:16 +0000 In-Reply-To: References: <20211215145633.5238-1-dwmw2@infradead.org> <761c1552-0ca0-403b-3461-8426198180d0@amd.com> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-NNF9tUzP2tOJLy2sYuBZ" User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-NNF9tUzP2tOJLy2sYuBZ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2021-12-16 at 16:52 -0600, Tom Lendacky wrote: > On baremetal, I haven't seen an issue. This only seems to have a problem= =20 > with Qemu/KVM. >=20 > With 191f08997577 I could boot without issues with and without the=20 > no_parallel_bringup. Only after I applied e78fa57dd642 did the failure ha= ppen. >=20 > With e78fa57dd642 I could boot 64 vCPUs pretty consistently, but when I= =20 > jumped to 128 vCPUs it failed again. When I moved the series to=20 > df9726cb7178, then 64 vCPUs also failed pretty consistently. >=20 > Strange thing is it is random. Sometimes (rarely) it works on the first= =20 > boot and then sometimes it doesn't, at which point it will reset and=20 > reboot 3 or 4 times and then make it past the failure and fully boot. Hm, some of that is just artifacts of timing, I'm sure. But now I'm staring at the way that early_setup_idt() can run in parallel on all CPUs, rewriting bringup_idt_descr and loading it. To start with, let's try unlocking the trampoline_lock much later, after cpu_init_exception_handling() has loaded the real IDT.=20 I think we can probably make secondaries load the real IDT early and never use bringup_idt_descr at all, can't we? But let's see if this makes it go away, to start with... diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 0cd6373bc3f2..2307f7575ab4 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -59,7 +59,7 @@ #include #include #include - +#include #include "cpu.h" =20 u32 elf_hwcap2 __read_mostly; @@ -2060,6 +2060,7 @@ void cpu_init_secondary(void) * on this CPU in cpu_init_exception_handling(). */ cpu_init_exception_handling(); + clear_bit(0, (unsigned long *)trampoline_lock); cpu_init(); } #endif diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 3e4c3c416bce..db01b56574cd 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -273,14 +273,6 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_= GLOBAL) */ movq initial_stack(%rip), %rsp =20 - /* Drop the realmode protection. For the boot CPU the pointer is NULL! */ - movq trampoline_lock(%rip), %rax - testq %rax, %rax - jz .Lsetup_idt - lock - btrl $0, (%rax) - -.Lsetup_idt: /* Setup and Load IDT */ pushq %rsi call early_setup_idt --=-NNF9tUzP2tOJLy2sYuBZ Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCECow ggUcMIIEBKADAgECAhEA4rtJSHkq7AnpxKUY8ZlYZjANBgkqhkiG9w0BAQsFADCBlzELMAkGA1UE BhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgG A1UEChMRQ09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBSU0EgQ2xpZW50IEF1dGhl bnRpY2F0aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0EwHhcNMTkwMTAyMDAwMDAwWhcNMjIwMTAxMjM1 OTU5WjAkMSIwIAYJKoZIhvcNAQkBFhNkd213MkBpbmZyYWRlYWQub3JnMIIBIjANBgkqhkiG9w0B AQEFAAOCAQ8AMIIBCgKCAQEAsv3wObLTCbUA7GJqKj9vHGf+Fa+tpkO+ZRVve9EpNsMsfXhvFpb8 RgL8vD+L133wK6csYoDU7zKiAo92FMUWaY1Hy6HqvVr9oevfTV3xhB5rQO1RHJoAfkvhy+wpjo7Q 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