From mboxrd@z Thu Jan 1 00:00:00 1970 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C39C9C43334 for ; Tue, 14 Jun 2022 15:43:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1884A6B00A3; Tue, 14 Jun 2022 11:43:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1384F6B00A4; Tue, 14 Jun 2022 11:43:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F40836B00A5; Tue, 14 Jun 2022 11:43:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id E4E5A6B00A3 for ; Tue, 14 Jun 2022 11:43:54 -0400 (EDT) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id B90E060270 for ; Tue, 14 Jun 2022 15:43:54 +0000 (UTC) X-FDA: 79577261988.06.83769E6 Received: from mail-pj1-f41.google.com (mail-pj1-f41.google.com [209.85.216.41]) by imf13.hostedemail.com (Postfix) with ESMTP id 26BC120094 for ; Tue, 14 Jun 2022 15:43:53 +0000 (UTC) Received: by mail-pj1-f41.google.com with SMTP id v11-20020a17090a4ecb00b001e2c5b837ccso12137226pjl.3 for ; Tue, 14 Jun 2022 08:43:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=v7R3AU8eay3jFLbgOIExfUOsI5EdQhSbQRsdrHwotJw=; b=ehHmS6K8XnQ2SrjXe0GbtBVb7v2r/7AcW7sIGGWUjjSMTDgZG99AgHzHG+emgMuy78 oJg0pzPpvCtiu3YGgen4uTSgcaIQrSr23K6ULxNbRwaPO6Yv/2KLZXVbn7tBDmMEA+JB /OEgfzksSH1MA4vy1vX+tyavgxHUWffoUJgQft6aRg+kifewPpPNV53IAZXgkNQBHTWY Ql4t/SIvDY0bHTODMSic0GJaxZI6gfqzTzQMvW4xvnj/rmFRw+k9nbzv081yS6sEUTLa VSazk4yWTKuGPfHB+dJmXxfbDPgU54AVHMrrKLFMMzFiEc/Rb9mMF6g9UULaB5YLhewT nzjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=v7R3AU8eay3jFLbgOIExfUOsI5EdQhSbQRsdrHwotJw=; b=oqy0Vh9n2ryFSztLWkVcK17YZsIEfSETy2k1misv17tWdOHfwGG0UEEIszY3r3nD8c ETmD46luG4ejHki37lji5TltHDtySPFaiIBXxskaHnWMYi6WheaijUYHyaTysmsDq3xD ki0Tib4AfD0s9waR4Fzi2YWI2pelbzgdn7TKB5CdQBScFNsorA3LPqetYAdE4areIUZM 9RA4jF1GS6ZmL0m4n2Q4zcZIfcbhJsIMsq0jX/u8HFBSjwvqmRctCNLbWWRN7Zv6HdXt qVEOI0boo2VG2eoaLIxywirQ7Si9QMc55+C7feOd0y/PXtmQUKR5zfwU85JjRKuHQhov nc6w== X-Gm-Message-State: AJIora9gTkvqk3EEZnhdJKCbA0T+jjFaVWgk5t4EFWUTXt08Mzneg4RN RzgjBG5pH/fRMvuI97nSjqwxRw== X-Google-Smtp-Source: AGRyM1sSpS8ksQoeFsAiBuqnaVFCfTWw36cqGK81vkz64eI2RfYURAd4rfysk6IagqiDsDg27788vA== X-Received: by 2002:a17:90a:fd0d:b0:1ea:b661:4fa1 with SMTP id cv13-20020a17090afd0d00b001eab6614fa1mr5238743pjb.46.1655221432801; Tue, 14 Jun 2022 08:43:52 -0700 (PDT) Received: from google.com (157.214.185.35.bc.googleusercontent.com. [35.185.214.157]) by smtp.gmail.com with ESMTPSA id v11-20020a1709028d8b00b00165105518f6sm7390006plo.287.2022.06.14.08.43.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Jun 2022 08:43:52 -0700 (PDT) Date: Tue, 14 Jun 2022 15:43:48 +0000 From: Sean Christopherson To: Michael Roth Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, Thomas Gleixner , Ingo Molnar , Joerg Roedel , Tom Lendacky , "H. Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Vitaly Kuznetsov , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Borislav Petkov , Vlastimil Babka , "Kirill A . Shutemov" , Andi Kleen , "Dr . David Alan Gilbert" , brijesh.ksingh@gmail.com, tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com Subject: Re: [PATCH v12 19/46] x86/kernel: Make the .bss..decrypted section shared in RMP table Message-ID: References: <20220307213356.2797205-1-brijesh.singh@amd.com> <20220307213356.2797205-20-brijesh.singh@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655221434; a=rsa-sha256; cv=none; b=tKoZvxjIAExJkNZaIw24f3iD7mmkfmW1yF1QTQ+srqetFB2nOei102I8PKl7FSMgmyuZNr 7BKyHqto+KEotNWWl+Bck/F9k3Y7i8prVxNQq4XrbrVKN+IhYz4GA3Gp/SbiHJ+B66Nr4a xq+j4QKxGNkkUovANYWYQ0pBLv/EmhI= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=ehHmS6K8; spf=pass (imf13.hostedemail.com: domain of seanjc@google.com designates 209.85.216.41 as permitted sender) smtp.mailfrom=seanjc@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655221434; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=v7R3AU8eay3jFLbgOIExfUOsI5EdQhSbQRsdrHwotJw=; b=ba6Vo3cm9JGsmXUHEozL3hxUYJwCfvkRfCayJZT235nIoPGZ6YRYg/m8DBO7NV25OLN0d7 KrOh8bIPSqffTOyx9TGC8rJi8m5zeLLpsyoyPtmBtPrcbEDk6v113R2elhFgME58g6nidy NG2ARP6/GJVYTW7lje9hc8I/IKwWg/k= X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 26BC120094 X-Stat-Signature: 5ca74tymsy34nij435mf1ksfw1qypurz Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=ehHmS6K8; spf=pass (imf13.hostedemail.com: domain of seanjc@google.com designates 209.85.216.41 as permitted sender) smtp.mailfrom=seanjc@google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1655221433-913721 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jun 14, 2022, Sean Christopherson wrote: > s/Brijesh/Michael > > On Mon, Mar 07, 2022, Brijesh Singh wrote: > > The encryption attribute for the .bss..decrypted section is cleared in the > > initial page table build. This is because the section contains the data > > that need to be shared between the guest and the hypervisor. > > > > When SEV-SNP is active, just clearing the encryption attribute in the > > page table is not enough. The page state need to be updated in the RMP > > table. > > > > Signed-off-by: Brijesh Singh > > --- > > arch/x86/kernel/head64.c | 13 +++++++++++++ > > 1 file changed, 13 insertions(+) > > > > diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c > > index 83514b9827e6..656d2f3e2cf0 100644 > > --- a/arch/x86/kernel/head64.c > > +++ b/arch/x86/kernel/head64.c > > @@ -143,7 +143,20 @@ static unsigned long __head sme_postprocess_startup(struct boot_params *bp, pmdv > > if (sme_get_me_mask()) { > > vaddr = (unsigned long)__start_bss_decrypted; > > vaddr_end = (unsigned long)__end_bss_decrypted; > > + > > for (; vaddr < vaddr_end; vaddr += PMD_SIZE) { > > + /* > > + * On SNP, transition the page to shared in the RMP table so that > > + * it is consistent with the page table attribute change. > > + * > > + * __start_bss_decrypted has a virtual address in the high range > > + * mapping (kernel .text). PVALIDATE, by way of > > + * early_snp_set_memory_shared(), requires a valid virtual > > + * address but the kernel is currently running off of the identity > > + * mapping so use __pa() to get a *currently* valid virtual address. > > + */ > > + early_snp_set_memory_shared(__pa(vaddr), __pa(vaddr), PTRS_PER_PMD); > > This breaks SME on Rome and Milan when compiling with clang-13. I haven't been > able to figure out exactly what goes wrong. printk isn't functional at this point, > and interactive debug during boot on our test systems is beyond me. I can't even > verify that the bug is specific to clang because the draconian build system for our > test systems apparently is stuck pointing at gcc-4.9. > > I suspect the issue is related to relocation and/or encrypting memory, as skipping > the call to early_snp_set_memory_shared() if SNP isn't active masks the issue. > I've dug through the assembly and haven't spotted a smoking gun, e.g. no obvious > use of absolute addresses. > > Forcing a VM through the same path doesn't fail. I can't test an SEV guest at the > moment because INIT_EX is also broken. The SEV INIT_EX was a PEBKAC issue. An SEV guest boots just fine with a clang-built kernel, so either it's a finnicky relocation issue or something specific to SME. > The crash incurs a very, very slow reboot, and I was out of cycles to work on this > about three hours ago. If someone on the AMD side can repro, it would be much > appreciated.