From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: mx.groups.io; dkim=missing; spf=pass (domain: redhat.com, ip: 209.132.183.28, mailfrom: lersek@redhat.com) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by groups.io with SMTP; Mon, 23 Sep 2019 11:35:11 -0700 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E8B7F197BCE0; Mon, 23 Sep 2019 18:35:10 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-2.rdu2.redhat.com [10.10.120.2]) by smtp.corp.redhat.com (Postfix) with ESMTP id AB3F45D9D5; Mon, 23 Sep 2019 18:35:03 +0000 (UTC) Subject: Re: [edk2-devel] [Qemu-devel] [PATCH 1/2] q35: implement 128K SMRAM at default SMBASE address From: "Laszlo Ersek" To: Igor Mammedov Cc: devel@edk2.groups.io, qemu-devel@nongnu.org, yingwen.chen@intel.com, phillip.goerl@oracle.com, alex.williamson@redhat.com, jiewen.yao@intel.com, jun.nakajima@intel.com, michael.d.kinney@intel.com, pbonzini@redhat.com, boris.ostrovsky@oracle.com, rfc@edk2.groups.io, joao.m.martins@oracle.com, Brijesh Singh References: <20190917130708.10281-1-imammedo@redhat.com> <20190917130708.10281-2-imammedo@redhat.com> <561f4440-7c06-10d7-80ce-bbfa810fec59@redhat.com> <20190920102855.3fe2b689@redhat.com> Message-ID: Date: Mon, 23 Sep 2019 20:35:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.70]); Mon, 23 Sep 2019 18:35:11 +0000 (UTC) Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 09/20/19 11:28, Laszlo Ersek wrote: > On 09/20/19 10:28, Igor Mammedov wrote: >> On Thu, 19 Sep 2019 19:02:07 +0200 >> "Laszlo Ersek" wrote: >> >>> Hi Igor, >>> >>> (+Brijesh) >>> >>> long-ish pondering ahead, with a question at the end. >> [...] >> >>> Finally: can you please remind me why we lock down 128KB (32 pages) at >>> 0x3_0000, and not just half of that? What do we need the range at >>> [0x4_0000..0x4_FFFF] for? >> >> >> If I recall correctly, CPU consumes 64K of save/restore area. >> The rest 64K are temporary RAM for using in SMI relocation handler, >> if it's possible to get away without it then we can drop it and >> lock only 64K required for CPU state. It won't help with SEV >> conflict though as it's in the first 64K. > > OK. Let's go with 128KB for now. Shrinking the area is always easier > than growing it. > >> On QEMU side, we can drop black-hole approach and allocate >> dedicated SMRAM region, which explicitly gets mapped into >> RAM address space and after SMI hanlder initialization, gets >> unmapped (locked). So that SMRAM would be accessible only >> from SMM context. That way RAM at 0x30000 could be used as >> normal when SMRAM is unmapped. > > I prefer the black-hole approach, introduced in your current patch > series, if it can work. Way less opportunity for confusion. > > I've started work on the counterpart OVMF patches; I'll report back. I've got good results. For this (1/2) QEMU patch: Tested-by: Laszlo Ersek I tested the following scenarios. In every case, I verified the OVMF log, and also the "info mtree" monitor command's result (i.e. whether "smbase-blackhole" / "smbase-window" were disabled or enabled). Mostly, I diffed these text files between the test scenarios (looking for desired / undesired differences). In the Linux guests, I checked / compared the dmesg too (wrt. the UEFI memmap). - unpatched OVMF (regression test), Fedora guest, normal boot and S3 - patched OVMF, but feature disabled with "-global mch.smbase-smram=off" (another regression test), Fedora guest, normal boot and S3 - patched OVMF, feature enabled, Fedora and various Windows guests (win7, win8, win10 families, client/server), normal boot and S3 - a subset of the above guests, with S3 disabled (-global ICH9-LPC.disable_s3=1), and obviously S3 resume not tested SEV: used 5.2-ish Linux guest, with S3 disabled (no support under SEV for that now): - unpatched OVMF (regression test), normal boot - patched OVMF but feature disabled on the QEMU cmdline (another regression test), normal boot - patched OVMF, feature enabled, normal boot. I plan to post the OVMF patches tomorrow, for discussion. (It's likely too early to push these QEMU / edk2 patches right now -- we don't know yet if this path will take us to the destination. For now, it certainly looks great.) Thanks Laszlo