From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from esa5.hc3370-68.iphmx.com (esa5.hc3370-68.iphmx.com [216.71.155.168]) by mx.groups.io with SMTP id smtpd.web09.7731.1580389805359266623 for ; Thu, 30 Jan 2020 05:10:05 -0800 Authentication-Results: mx.groups.io; dkim=pass header.i=@citrix.com header.s=securemail header.b=hX+MvOu8; spf=pass (domain: citrix.com, ip: 216.71.155.168, mailfrom: andrew.cooper3@citrix.com) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=citrix.com; s=securemail; t=1580389805; h=subject:to:cc:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=+I/OdJuW6E1EEL0tdPJPuPDJeU2NGzoITaLrHWB/fZA=; b=hX+MvOu8h6/+Zkvbb6rkODaWffhCwK5S007u+1YyjXD4avpgNOqo7W+h LOmXSgKfpm3517uK5ud9pIyy/6tf5vyMXvY2gp9EGDxvu5XgHxdJCk8G0 khEHddvDyfbjyK33vjYmHRovwT180UdZzJPKSgnYwIR/wI62evep5nf99 Y=; Authentication-Results: esa5.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none; spf=None smtp.pra=andrew.cooper3@citrix.com; spf=Pass smtp.mailfrom=Andrew.Cooper3@citrix.com; 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client-ip=162.221.158.21; receiver=esa5.hc3370-68.iphmx.com; envelope-from="Andrew.Cooper3@citrix.com"; x-sender="postmaster@mail.citrix.com"; x-conformance=sidf_compatible IronPort-SDR: NTFj2YOypNrpugAdilyS4NlfArlF+SNHRw+8SU0RFl+fhACQ056mTKJWp8Xy3Ecgfe0d4WEgqp rCV1bGH+2VRv8CA9rdgUjrq8V/Mcual1oWhhpFwkRzqGFC2cFFJztAnMnQLR5Yk63yHp/YD9qp jeaL0Po4f4FI6OhQ6pXQKQZvF9MCy++H83U66y80Sa1SBnUYewwSg8O2mOgU5Fma2ThA9EWooa 7mf7+159xzmcxbNK1WY4hsUXuJDfvHPmOehpICiQZV0X/JvAkAfNz7a9utdz67udJHEmCgeuN+ CDk= X-SBRS: 2.7 X-MesageID: 12046150 X-Ironport-Server: esa5.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.70,382,1574139600"; d="scan'208";a="12046150" Subject: Re: [Xen-devel] [PATCH 4/5] OvmfPkg/XenPlatformPei: Calibrate APIC timer frequency To: Anthony PERARD , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= CC: Julien Grall , Ard Biesheuvel , Jordan Justen , , Liming Gao , Michael D Kinney , , Laszlo Ersek References: <20200129121235.1814563-1-anthony.perard@citrix.com> <20200129121235.1814563-5-anthony.perard@citrix.com> <20200130091251.GB4679@Air-de-Roger> <20200130124431.GO1288@perard.uk.xensource.com> From: Andrew Cooper Openpgp: preference=signencrypt Autocrypt: addr=andrew.cooper3@citrix.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200130124431.GO1288@perard.uk.xensource.com> Return-Path: andrew.cooper3@citrix.com X-ClientProxiedBy: AMSPEX02CAS01.citrite.net (10.69.22.112) To AMSPEX02CL01.citrite.net (10.69.22.125) Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Content-Language: en-GB On 30/01/2020 12:44, Anthony PERARD wrote: > On Thu, Jan 30, 2020 at 10:12:51AM +0100, Roger Pau Monné wrote: >> On Wed, Jan 29, 2020 at 12:12:34PM +0000, Anthony PERARD wrote: >>> + Parameters.domid = DOMID_SELF; >>> + Parameters.gpfn = (UINTN) PagePtr >> EFI_PAGE_SHIFT; >>> + ReturnCode = XenHypercallMemoryOp (XENMEM_remove_from_physmap, &Parameters); >> I'm afraid this will leave a hole in the p2m, and hence freeing the >> page back to OVMF is wrong (I assume this is what FreePages does in >> CalibrateLapicTimer), as the physical address would be unpopulated >> after the call to XENMEM_remove_from_physmap. > I guess there's more refactoring to do in OVMF, there are other's of > this kind of call, mostly in the PV drivers, XenBusDxe. > >>> + >>> + SharedInfo = AllocatePages (1); >> Hm, it's not the best approach to use a regular memory page to map the >> shared info: mapping it is very likely to cause superpage shattering, >> and once unmapped it leaves a hole in the p2m. > :-( > >> As a reference you could map the shared info page at maximum physical >> address allowed (after checking it's not populated) like Wei is doing >> for the Xen on HyperV work. > I'll look at what can be done with OVMF. > > Is there some kind of information that Xen could give? Or is it all > information that OVMF should keep track of? Or if Xen only have > XENMEM_memory_map, then OVMF already have this information. We need to actually tackle the memory problem, and provide something correct via XENMEM_memory_map (/similar). So far, noone has actually started to try fixing the problem.  Perhaps now is a good enough kick to get started. ~Andrew