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Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it
From: |
Edgar E. Iglesias |
Subject: |
Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode |
Date: |
Thu, 9 Apr 2015 23:58:28 +1000 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, Apr 09, 2015 at 03:06:39PM +0200, Paolo Bonzini wrote:
>
>
> On 09/04/2015 14:47, Peter Maydell wrote:
> > On 9 April 2015 at 13:20, Paolo Bonzini <address@hidden> wrote:
> >> This is an example of usage of attributes in a device model. It lets
> >> you block flash writes unless the CPU is in secure mode. Enabling it
> >> currently requires a -readconfig file:
> >>
> >> [global]
> >> driver = "cfi.pflash01"
> >> property = "secure"
> >> value = "on"
> >>
> >> because the driver includes a "."; however, I plan to enable this through
> >> the command line for the final version of the patches.
> >
> > Are real flash devices ever wired up like this?
>
> On x86 machines it is almost exactly like this. I'm implementing x86
> system management mode, and I'm reusing MEMTXATTRS_SECURE for it.
>
> Recent x86 chipsets make this a run-time setting, rather than a static
> setting, but the idea is the same. It is a run-time setting (chipset
> register) so that the firmware can do some initial detection of the
> flash outside system management mode. Then it writes a 1 to the
> register, and finally it writes a 1 to a "lock" register so that the
> first register becomes read-only.
>
> The above scheme was actually more complicated, and allowed a race that
> let you bypass the protection. So, even more recent machines have some
> additional complication, whereby flash accesses are only allowed if
> _all_ processors are in system management mode. Again, it is a run-time
> setting.
>
> QEMU emulates a slightly older chipset, which is why I'm making it a
> static property. The static property is also much harder to get wrong
> and insecure by mistake.
Hi Paulo,
How would this work with XIP off the romd region?
Without s/ns address spaces, CPUs in NS state will be able to execute
and access data while in ROMD state won't they?
I may be missing something...
Cheers,
Edgar
- [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode, Paolo Bonzini, 2015/04/09
- [Qemu-devel] [PATCH 1/3] pflash_cfi01: change big-endian property to BIT type, Paolo Bonzini, 2015/04/09
- [Qemu-devel] [PATCH 3/3] pflash_cfi01: add secure property, Paolo Bonzini, 2015/04/09
- [Qemu-devel] [PATCH 2/3] pflash_cfi01: change to new-style MMIO accessors, Paolo Bonzini, 2015/04/09
- Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode, Peter Maydell, 2015/04/09
- Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode, Paolo Bonzini, 2015/04/09
- Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode, Peter Maydell, 2015/04/09
- Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode,
Edgar E. Iglesias <=
- Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode, Paolo Bonzini, 2015/04/09
- Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode, Laszlo Ersek, 2015/04/09
- Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode, Paolo Bonzini, 2015/04/09
- Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode, Edgar E. Iglesias, 2015/04/09
- Re: [Qemu-devel] [RFC PATCH 0/3] pflash_cfi01: allow reading/writing it only in secure mode, Peter Maydell, 2015/04/10