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From: nmm1 on 22 Jul 2010 14:47
In article <34ea667e-779a-44d8-ab63-c032df1cb067(a)q35g2000yqn.googlegroups.com>,
Robert Myers <rbmyersusa(a)gmail.com> wrote:
>
>At a time when vector processors were still a fading memory (even in
>the US), an occasional article would mention that "vector computers"
>were easier to use for many scientists than thousands of cots
>processors hooked together by whatever.

Yup. And more recently, among the very few people who used them.

>The real problem is not in how the computation is organized, but in
>how memory is accessed. Replicating the memory access style of the
>early Cray architectures isn't possible beyond a very limited memory
>size, but it sure would be nice to figure out a way to simulate the
>experience.

Hitachi did pretty well with the SR2201 and SR8000. But it was
still expensive.


Regards,
Nick Maclaren.
From: Robert Myers on 22 Jul 2010 16:10
George Neuner wrote:
> On Wed, 21 Jul 2010 21:48:38 -0700, Andy Glew <"newsgroup at
> comp-arch.net"> wrote:
>
>> On 7/21/2010 3:46 PM, Alex McDonald wrote:
>>
>>> Can you be more explicit on this? I understand the lack of complete
>>> virtualization is an issue with the x86, but I'm fascinated by your
>>> claim of exploitable design flaws; what are they?
>> The 80386 and othrr processors, up until recently, were incompletely
>> self virtualizing.
>>
>> However, as far as I know, with the addition of VMX at Intel, and
>> Pacifica at AMD, the x86 processors are now completely self virtualizing.
>
> Yes, but last year there was a claim of some rootkit type hack that
> could take control of Intel's hypervisor. I don't know any details, I
> just remember seeing a headline.
>

Yes, there are proposed exploits.

One big reason that IBM mainframes are not a plausible target for
hackers is that not many hackers own one. Monoculture in hardware is
risky in the same way that monoculture in agriculture is risky:
parasitic invaders can expend more energy exploring a narrow and
well-defined target.

I assume that hacking of x86 hypervisors will be a much bigger problem
than hacking of IBM propietary hypervisors has ever been, but only in
part because IBM is historically marginally more careful about what it
sells.

Robert.
From: MitchAlsup on 22 Jul 2010 18:26
On Jul 22, 1:41 pm, Robert Myers <rbmyers...(a)gmail.com> wrote:
> The real problem is not in how the computation is organized, but in
> how memory is accessed.  Replicating the memory access style of the
> early Cray architectures isn't possible beyond a very limited memory
> size, but it sure would be nice to figure out a way to simulate the
> experience.

One of the reasons CRAY machines lived <somewhat> longer than some of
the other vector supercomputers was that <at least> CRAY I/O system
could operate at vastly higher performance levels than their Japanees
counterparts. Thus, while the CPU was crunching the I/O system could
be shoveling data around at vast I/O rates, so that when the CPU was
done crunching, the next unit of work was ready to be tackled.

This is not easy with TeraByte sized data footprints and sub-GigaByte
main memory footprints.

Mitch
From: robertwessel2 on 23 Jul 2010 01:21
On Jul 22, 1:16 pm, George Neuner <gneun...(a)comcast.net> wrote:
> On Wed, 21 Jul 2010 21:48:38 -0700, Andy Glew <"newsgroup at
>
> comp-arch.net"> wrote:
> >On 7/21/2010 3:46 PM, Alex McDonald wrote:
>
> >> Can you be more explicit on this? I understand the lack of complete
> >> virtualization is an issue with the x86, but I'm fascinated by your
> >> claim of exploitable design flaws; what are they?
>
> >The 80386 and othrr processors, up until recently, were incompletely
> >self virtualizing.
>
> >However, as far as I know, with the addition of VMX at Intel, and
> >Pacifica at AMD, the x86 processors are now completely self virtualizing..
>
> Yes, but last year there was a claim of some rootkit type hack that
> could take control of Intel's hypervisor.  I don't know any details, I
> just remember seeing a headline.


You probably mean the SubVirt hack. That exploited the virtualization
hardware to hack the target OS. IOW, the idea was to inject a VM
hypervisor, and then continue running what the user thought was the
native OS under that. And of course a hypervisor is capable of pretty
much any level of mischief.

There have also been attacks on several hypervisors, but most
vulnerabilities occur because you can send commands of various sorts
from a guest to the hypervisor (for example, "attach virtual disk
'someotheros/sysvol' to me"), that were often not properly secured.
And before anyone objects, being able to issue commands to the
hypervisor is very useful - you can, for example, request access to a
particular real device, or change the amount of memory in your guest,
etc.


From: robertwessel2 on 23 Jul 2010 01:25
On Jul 21, 11:48 pm, Andy Glew <"newsgroup at comp-arch.net"> wrote:
> On 7/21/2010 3:46 PM, Alex McDonald wrote:
>
>
>
>
>
> > On 20 July, 22:31, "David L. Craig"<dlc....(a)gmail.com>  wrote:
> >> On Jul 20, 2:49 pm, Robert Myers<rbmyers...(a)gmail.com>  wrote:
>
> >>> I doubt if mass-market x86 hypervisors ever crossed the
> >>> imagination at IBM, even as the barbarians were at the
> >>> gates.
>
> >> You'd be wrong.  A lot of IBMers and customer VMers were
> >> watching what Intel was going to do with the 80386 next
> >> generations to support machine virtualization.  While
> >> Intel claimed it was coming, by mainframe standards, they
> >> showed they just weren't serious.  Not only can x86 not
> >> fully virtualize itself, it has known design flaws that
> >> can be exploited to compromise the integrity of its
> >> guests and the hypervisor.  That it is used widely as a
> >> consolidation platform boggles the minds of those in the
> >> know.  We're waiting for the eventual big stories.
>
> > Can you be more explicit on this? I understand the lack of complete
> > virtualization is an issue with the x86, but I'm fascinated by your
> > claim of exploitable design flaws; what are they?
>
> The 80386 and othrr processors, up until recently, were incompletely
> self virtualizing.
>
> However, as far as I know, with the addition of VMX at Intel, and
> Pacifica at AMD, the x86 processors are now cimpldetely self virtualizing..


It's not clear to me that the VMX extensions themselves virtualize
well (IOW, can you emulate VMX for the guests, so you can’t have
nested VMs using VMX?). In fact, as I read the docs, they don't.
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