From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by mx.groups.io with SMTP id smtpd.web10.58476.1673538304968730655 for ; Thu, 12 Jan 2023 07:45:05 -0800 Authentication-Results: mx.groups.io; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=TtEsnFgj; spf=pass (domain: redhat.com, ip: 170.10.129.124, mailfrom: lersek@redhat.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673538304; h=from:from: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=U4zsHdHsoxO8w8ErgREHe6rSFROShXS2U9SqzNj2jQY=; b=TtEsnFgjiLwjaGbOctF/HucL94naR9jS9C2glbSEkPZ0+8Q+cQI2+WLkzFkUMYnSCWXFmK Pcge6mP660T+hJ2Hny2drUkFBAcqfIbTyMz4mHUTnP2Wn4yaKC1u3Qg4FyQRcLnSnnzXCC P8ftqliaZyxNtMdoezeWrX5zJIseUuk= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-5-lGlBUBpTN9OpRw3_7R5e_A-1; Thu, 12 Jan 2023 10:44:59 -0500 X-MC-Unique: lGlBUBpTN9OpRw3_7R5e_A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4843F2801E5E; Thu, 12 Jan 2023 15:44:59 +0000 (UTC) Received: from [10.39.192.93] (unknown [10.39.192.93]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 03B2F1121314; Thu, 12 Jan 2023 15:44:57 +0000 (UTC) Message-ID: Date: Thu, 12 Jan 2023 16:44:56 +0100 MIME-Version: 1.0 Subject: Re: [PATCH v2 2/4] OvmfPkg/PlatformInitLib: Add PlatformGetLowMemoryCB To: Gerd Hoffmann Cc: devel@edk2.groups.io, Pawel Polawski , Jiewen Yao , Oliver Steffen , Jordan Justen , Ard Biesheuvel References: <20230110082123.159521-1-kraxel@redhat.com> <20230110082123.159521-3-kraxel@redhat.com> <043b03d6-0a6b-c533-255b-24a7805d5cca@redhat.com> <20230111072925.l47t4ahgynqjyegq@sirius.home.kraxel.org> <4ace3789-7192-0c53-b4b2-f62f907176d0@redhat.com> <20230111152341.d3p6iy5pml7shfvk@sirius.home.kraxel.org> <20230112140340.wayqeuwh2d3gcp3s@sirius.home.kraxel.org> From: "Laszlo Ersek" In-Reply-To: <20230112140340.wayqeuwh2d3gcp3s@sirius.home.kraxel.org> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/12/23 15:03, Gerd Hoffmann wrote: > Hi, > >>> I think it should actually simplify things. All the inconsistencies we >>> have (as you outlined above) due to the hole punching and edk2 >>> supporting only a single range for 32bit mmio should go away, and we >>> will have less address space layout differences between q35 and pc. >> >> We've tried 0xE000_0000 in the past, in commit 75136b29541b. >> >> But had to revert it in commit eb4d62b0779c, due to 0xE000_0000 tickling >> a bug in QEMU. >> >> The bug tickling was actually reported by you :) See >> . > > Oh. I totally forgot about that. The patch from (I think) 2019 which > added _CRS for the range below the MMCONFIG should have fixed that, and > with recent qemu everything works fine. > > I suspect we can't easily detect whenever qemu is broken or not. Hmm. > > Is more than three years being passed enough to just do it > unconditionally and effectively raise the bar for the minimum > supported qemu version? Well, in the other thread ("[PATCH v2] OvmfPkg/PlatformInitLib: catch QEMU's CPU hotplug reg block regression"), I'm proposing a hard hang for a QEMU bug that's not been fixed in *any* public release yet, and will only be fixed in v8 :) Can you determine the exact QEMU bugfix (commit hash) and the first QEMU release that included it? Maybe even build & test that version? If we determine the minimum functional QEMU version precisely, and it's like v5 or v6, making it the "official minimum" should be fine. > >> (Well, if you mean to keep the same logic for both i440fx adn q35, >> that's OK then.) > > Yes, it would be Uc32Base. > > LowMemory and Uc32Base are identical anyway most of the time due to qemu > preferring gigabyte pages when possible, you need odd memory sizes like > 1.5 or 2.5 GB to see they actually can be different. > Thanks Laszlo