From: Igor Mammedov <imammedo@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Yao, Jiewen" <jiewen.yao@intel.com>,
Laszlo Ersek <lersek@redhat.com>,
edk2-devel-groups-io <devel@edk2.groups.io>,
edk2-rfc-groups-io <rfc@edk2.groups.io>,
qemu devel list <qemu-devel@nongnu.org>,
"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: CPU hotplug using SMM with QEMU+OVMF
Date: Fri, 16 Aug 2019 09:42:12 +0200 [thread overview]
Message-ID: <20190816094212.28184314@redhat.com> (raw)
In-Reply-To: <f6c58790-7298-d991-844e-48f4a9dc8937@redhat.com>
On Thu, 15 Aug 2019 18:24:53 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:
> On 15/08/19 18:07, Igor Mammedov wrote:
> > Looking at Q35 code and Seabios SMM relocation as example, if I see it
> > right QEMU has:
> > - SMRAM is aliased from DRAM at 0xa0000
> > - and TSEG steals from the top of low RAM when configured
> >
> > Now problem is that default SMBASE at 0x30000 isn't backed by anything
> > in SMRAM address space and default SMI entry falls-through to the same
> > location in System address space.
> >
> > The later is not trusted and entry into SMM mode will corrupt area + might
> > jump to 'random' SMI handler (hence save/restore code in Seabios).
> >
> > Here is an idea, can we map a memory region at 0x30000 in SMRAM address
> > space with relocation space/code reserved. It could be a part of TSEG
> > (so we don't have to invent ABI to configure that)?
>
> No, there could be real mode code using it.
My impression was that QEMU/KVM's SMM address space is accessible only from
CPU in SMM mode, so SMM CPU should access in-depended SMRAM at 0x30000 in
SMM address space while not SMM CPUs (including real mode) should access
0x30000 from normal system RAM.
> What we _could_ do is
> initialize SMBASE to 0xa0000, but I think it's better to not deviate too
> much from processor behavior (even if it's admittedly a 20-years legacy
> that doesn't make any sense).
Agreed, it's better to follow spec, that's one of the reasons why I was toying
with idea of using separate SMRAM at 0x30000 mapped only in SMM address space.
Practically we would be following spec: SDM: 34.4 SMRAM
"
System logic can use the SMI acknowledge transaction or the assertion of the SMIACT# pin to decode accesses to
the SMRAM and redirect them (if desired) to specific SMRAM memory. If a separate RAM memory is used for
SMRAM, system logic should provide a programmable method of mapping the SMRAM into system memory space
when the processor is not in SMM. This mechanism will enable start-up procedures to initialize the SMRAM space
(that is, load the SMI handler) before executing the SMI handler during SMM.
"
Another benefit that gives us, is that we won't have to pull in
all existing CPUs into SMM (essentially another stop_machine) to
guarantee exclusive access to 0x30000 in normal RAM.
>
> Paolo
prev parent reply other threads:[~2019-08-16 7:42 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-13 14:16 CPU hotplug using SMM with QEMU+OVMF Laszlo Ersek
2019-08-13 16:09 ` Laszlo Ersek
2019-08-13 16:18 ` Laszlo Ersek
2019-08-14 13:20 ` Yao, Jiewen
2019-08-14 14:04 ` Paolo Bonzini
2019-08-15 9:55 ` Yao, Jiewen
2019-08-15 16:04 ` Paolo Bonzini
2019-08-15 15:00 ` [edk2-devel] " Laszlo Ersek
2019-08-15 16:16 ` Igor Mammedov
2019-08-15 16:21 ` Paolo Bonzini
2019-08-16 2:46 ` Yao, Jiewen
2019-08-16 7:20 ` Paolo Bonzini
2019-08-16 7:49 ` Yao, Jiewen
2019-08-16 20:15 ` Laszlo Ersek
2019-08-16 22:19 ` Alex Williamson
2019-08-17 0:20 ` Yao, Jiewen
2019-08-18 19:50 ` Paolo Bonzini
2019-08-18 23:00 ` Yao, Jiewen
2019-08-19 14:10 ` Paolo Bonzini
2019-08-21 12:07 ` Laszlo Ersek
2019-08-21 15:48 ` [edk2-rfc] " Michael D Kinney
2019-08-21 17:05 ` Paolo Bonzini
2019-08-21 17:25 ` Michael D Kinney
2019-08-21 17:39 ` Paolo Bonzini
2019-08-21 20:17 ` Michael D Kinney
2019-08-22 6:18 ` Paolo Bonzini
2019-08-22 18:29 ` Laszlo Ersek
2019-08-22 18:51 ` Paolo Bonzini
2019-08-23 14:53 ` Laszlo Ersek
2019-08-22 20:13 ` Michael D Kinney
2019-08-22 17:59 ` Laszlo Ersek
2019-08-22 18:43 ` Paolo Bonzini
2019-08-22 20:06 ` Michael D Kinney
2019-08-22 22:18 ` Paolo Bonzini
2019-08-22 22:32 ` Michael D Kinney
2019-08-22 23:11 ` Paolo Bonzini
2019-08-23 1:02 ` Michael D Kinney
2019-08-23 5:00 ` Yao, Jiewen
2019-08-23 15:25 ` Michael D Kinney
2019-08-24 1:48 ` Yao, Jiewen
2019-08-27 18:31 ` Igor Mammedov
2019-08-29 17:01 ` Laszlo Ersek
2019-08-30 14:48 ` Igor Mammedov
2019-08-30 18:46 ` Laszlo Ersek
2019-09-02 8:45 ` Igor Mammedov
2019-09-02 19:09 ` Laszlo Ersek
2019-09-03 14:53 ` [Qemu-devel] " Igor Mammedov
2019-09-03 17:20 ` Laszlo Ersek
2019-09-04 9:52 ` imammedo
2019-09-05 13:08 ` Laszlo Ersek
2019-09-05 15:45 ` Igor Mammedov
2019-09-05 15:49 ` [PATCH] q35: lpc: allow to lock down 128K RAM at default SMBASE address Igor Mammedov
2019-09-09 19:15 ` Laszlo Ersek
2019-09-09 19:20 ` Laszlo Ersek
2019-09-10 15:58 ` Igor Mammedov
2019-09-11 17:30 ` Laszlo Ersek
2019-09-17 13:11 ` [edk2-devel] " Igor Mammedov
2019-09-17 14:38 ` [staging/branch]: CdePkg - C Development Environment Package Minnow Ware
2019-08-26 15:30 ` [edk2-rfc] [edk2-devel] CPU hotplug using SMM with QEMU+OVMF Laszlo Ersek
2019-08-27 16:23 ` Igor Mammedov
2019-08-27 20:11 ` Laszlo Ersek
2019-08-28 12:01 ` Igor Mammedov
2019-08-29 16:25 ` Laszlo Ersek
2019-08-30 13:49 ` [Qemu-devel] " Igor Mammedov
2019-08-22 17:53 ` Laszlo Ersek
2019-08-16 20:00 ` Laszlo Ersek
2019-08-15 16:07 ` Igor Mammedov
2019-08-15 16:24 ` Paolo Bonzini
2019-08-16 7:42 ` Igor Mammedov [this message]
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