Re: [Qemu-devel] [edk2-rfc] [edk2-devel] CPU hotplug using SMM with QEMU+OVMF

From: "Kinney, Michael D" <michael.d.kinney@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Laszlo Ersek <lersek@redhat.com>,
	"rfc@edk2.groups.io" <rfc@edk2.groups.io>,
	"Yao, Jiewen" <jiewen.yao@intel.com>,
	"Kinney, Michael D" <michael.d.kinney@intel.com>
Cc: "Chen, Yingwen" <yingwen.chen@intel.com>,
	"devel@edk2.groups.io" <devel@edk2.groups.io>,
	Phillip Goerl <phillip.goerl@oracle.com>,
	qemu devel list <qemu-devel@nongnu.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	"Nakajima, Jun" <jun.nakajima@intel.com>,
	Igor Mammedov <imammedo@redhat.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Joao Marcal Lemos Martins <joao.m.martins@oracle.com>
Subject: Re: [Qemu-devel] [edk2-rfc] [edk2-devel] CPU hotplug using SMM with QEMU+OVMF
Date: Fri, 23 Aug 2019 01:02:43 +0000	[thread overview]
Message-ID: <E92EE9817A31E24EB0585FDF735412F5B9DA2346@ORSMSX113.amr.corp.intel.com> (raw)
In-Reply-To: <3661c0c5-3da4-1453-a66a-3e4d4022e876@redhat.com>

Paolo,

I find the following links related to the discussions here
along with one example feature called GENPROTRANGE.

https://csrc.nist.gov/CSRC/media/Presentations/The-Whole-is-Greater/images-media/day1_trusted-computing_200-250.pdf
https://cansecwest.com/slides/2017/CSW2017_Cuauhtemoc-Rene_CPU_Hot-Add_flow.pdf
https://www.mouser.com/ds/2/612/5520-5500-chipset-ioh-datasheet-1131292.pdf

Best regards,

Mike

> -----Original Message-----
> From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> Sent: Thursday, August 22, 2019 4:12 PM
> To: Kinney, Michael D <michael.d.kinney@intel.com>;
> Laszlo Ersek <lersek@redhat.com>; rfc@edk2.groups.io;
> Yao, Jiewen <jiewen.yao@intel.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>;
> devel@edk2.groups.io; qemu devel list <qemu-
> devel@nongnu.org>; Igor Mammedov <imammedo@redhat.com>;
> Chen, Yingwen <yingwen.chen@intel.com>; Nakajima, Jun
> <jun.nakajima@intel.com>; Boris Ostrovsky
> <boris.ostrovsky@oracle.com>; Joao Marcal Lemos Martins
> <joao.m.martins@oracle.com>; Phillip Goerl
> <phillip.goerl@oracle.com>
> Subject: Re: [edk2-rfc] [edk2-devel] CPU hotplug using
> SMM with QEMU+OVMF
> 
> On 23/08/19 00:32, Kinney, Michael D wrote:
> > Paolo,
> >
> > It is my understanding that real HW hot plug uses the
> SDM defined
> > methods.  Meaning the initial SMI is to 3000:8000 and
> they rebase to
> > TSEG in the first SMI.  They must have chipset specific
> methods to
> > protect 3000:8000 from DMA.
> 
> It would be great if you could check.
> 
> > Can we add a chipset feature to prevent DMA to 64KB
> range from
> > 0x30000-0x3FFFF and the UEFI Memory Map and ACPI
> content can be
> > updated so the Guest OS knows to not use that range for
> DMA?
> 
> If real hardware does it at the chipset level, we will
> probably use Igor's suggestion of aliasing A-seg to
> 3000:0000.  Before starting the new CPU, the SMI handler
> can prepare the SMBASE relocation trampoline at
> A000:8000 and the hot-plugged CPU will find it at
> 3000:8000 when it receives the initial SMI.  Because this
> is backed by RAM at 0xA0000-0xAFFFF, DMA cannot access it
> and would still go through to RAM at 0x30000.
> 
> Paolo