Breaking BIOS: enabling VT-x virtualization support on Acer Aspire One netbook

https://sudonull.com/post/137275-Breaking-BIOS-enabling-VT-x-virtualization-support-on-Acer-Aspire-One-netbook

by userbinator • 4 years ago

133 78 4 years ago

2012 should be added to the title.

FWIW the CPU in question is a 45nm dual-core, four-thread, 1,66 GHz Intel Atom chip that supports a max of 2GB of RAM. It was Intel's X86 alternative to ARM for phones/tablets.

Its micro-architecture was completely different and far more simpler and lower performing than Intel's Pentium or Core chips of the time in order to massively reduce die-size and save cost. Therefore it was slow and under-powered even back then in 2011, even without these artificial limitations put in place for market segmentation. Just ask anyone who used Atom chips of that era.

At the time you would often find these chips in cheap Netbooks and Tablets, usually by Asus, and running a bare bones Linux distro was the only way to get anything usable out of them, as getting run over by a bus was a more enjoyable UX than running windows on them.

In a way, those cheap, light, portable Netbooks were ahead of their time, held back mostly by the low performance of the low power chips of the era, the bloat of Windows of the era and the jankyness of bare bones Linux distros of the era that wouldn't ship with the mainstream apps people used on Windows.

So as cool as this hack of removing the artificial limitations is, I'm not sure how much this really helps to make a case for using this CPU for OS virtualization using Windows VirtualBox on all four threads, considering the already severely limited performance and RAM.

segfaultbuserr2• 4 years ago

A more useful hack is unlocking AES-NI with the same method. Some laptops have AES instructions permanently disabled on boot via BIOS by the OEM to comply with regional cryptography regulations, such as some Lenovo Thinkpad models in Russia. In the 2010s, disassembling the BIOS and patching a single line away can regain hardware AES functionality. Unfortunately it's no longer possible after Boot Guard's BIOS lockdown.

Avamander• 4 years ago

Reference for that last sentence?

causi3• 4 years ago

The first generation Atoms were some of the worst chips ever made. By the end with the Bay Trail and Cherry Trail chips they were quite good, but Intel killed them in favor of M-series chips with the same performance per watt but five times the price tag.

fps_doug• 4 years ago

Bayfail was utterly broken on Linux until two years ago or so. There is a bugzilla entry with more than 1000 replies. And it appears that some platforms with that CPU still have issues with Linux, which according to that issue is yet another bug.

squarefoot2• 4 years ago

Earlier Atoms were close to crap for desktops, but they still have some uses.

I used a N455 based netbook for years as a motorcycle-laptop with a stripped down Debian. Unfortunately I didn't know about Alpine Linux back then, which could likely have made it a lot faster. Also, my home NAS uses a D410 CPU which is enough to support two ZFS pools and other services.

Nitrolo• 4 years ago

My first ever computer was a laptop with a first gen Atom and 1GB of RAM. Single-core, no hyperthreading. I was super excited and loved it, but it was so slow that it felt unusable even to me as a young teenager that didn't know any better.

Guess I should be thankful though, in trying to get it to be faster I discovered that some Linux distros can be very lightweight, and it started me down a rabbit hole I'm still going down.

triyambakam• 4 years ago

That's the same computer I learned to program with. I was forced to use vim because of system resources. And now I'm glad.

actionfromafar• 4 years ago

TinyXP ran very well on this class of computers, especially for as long as Firefox supported XP, it was a really useful platform.

Sort of like a chromebook before chromebook.

I later did a lot of C, PHP and Python programming in Linux + Emacs on such a computer, so not completely useless.

phire• 4 years ago

Buying an atom netbook was what helped me learn about the difference between in-order and out-of-order CPUs.

I actually upgrade from the 1.66gz atom to a 1.3ghz ULV core 2 duo, and it was way faster.

jkepler2• 4 years ago

For nearly 10 years I used a compact netbook with an Intel Atom Z530 1.6 GHz and 1G RAM, a Nokia Booklet 3G. I swapped the HDD for an SDD, and given its fanless unibody aluminum design and its 10.1in 1280x720 screen, it was silent and useable for basic office computing and 720p video, with a full-sized HDMI out. Even with Debian I used to get 6 to 7 hours of battery life. I used it extensively for note taking, dabbling in Python, and writing. It was slow, but more reliable and less buggy than running Debian on my older MacBook Pro (which had hardly any battery life left). I used the Nokia Booklet until its motherboard died in 2018, and I still miss that little machine's compact simplicity and utility.

randac• 4 years ago

I dodged the Atom and picked up an Acer 1810tz. 4gb RAM, intel U4100 CPU, ran rings around netbooks at the time and I still use it here and there to this day. Probably the best keyboard I've ever used on such a small device.

snvzz• 4 years ago

Even for in-order vs out-of-order, there's slower and faster.

Early atoms were really slow, compared to e.g. a SiFive P270, which is also in-order.

Out-of-order CPUs exist that are much slower. After all, in-order CPUs can be superscalar still.

dspillett2• 4 years ago

reduce die-size and save cost.

reducing power consumption was also a goal, which this worked for too. Though the early models at least were paired with hungry chipsets that negated most of that benefit.

ChuckNorris898• 4 years ago

Being battery efficient is irrelevant if it comes at the cost of drastic reductions in performance that make the device unusable. The sales numbers reflected this consumer choice in that era.

sidewndr462• 4 years ago

it was slow and under-powered

As someone who used one of these laptops as a daily driver for years, I disagree. The CPU was quite powerful. I would regularly use it to take notes in class, do development work (with an IDE) & browse the web. Compilation of larger components could be quite slow.

If you didn't insist on running the latest desktop environment with a bazillion bizarre graphical effects, it worked without issue. Battery life was 'good enough' that I could get a couple hours of regular usage.

Fast forward to today & many "productivity" applications like Microsoft Teams are so bloated they consume more memory than the entirety of that system had.

skykooler• 4 years ago

Same; I had an EeePC as my main laptop for four years. Never really felt slow, aside from when compiling software (I distinctly remember installing MacPorts on my hackintosh partition and it taking three hours to compile the base set of packages).

ChuckNorris898• 4 years ago

As someone who used one of these laptops as a daily driver for years, I disagree. The CPU was quite powerful.

The benchmarks, reviews and poor sales disagreed with you. Maybe it wasn't under-powered for your standards and needs back then, but compared to what the mainstream laptop market of the time, they were very slow in windows apps which is what most consumers ran back then.

userbinator4• 4 years ago

Its micro-architecture was completely different and far more simpler and lower performing than Intel's Pentium or Core chips of the time in order to massively reduce die-size and save cost.

...and yet they decided to add VT-x for some reason, but disable it?

ChuckNorris898• 4 years ago

It's called market segmentation. It has been happening for decades.

You can also buy cars with included heated seats and they're disabled unless you pay extra.

monocasa• 4 years ago

Atom cores were getting pitched a lot for micro servers at the time. At the time containerizing tech hadn't really taken off; Vagrant using full VMs was still bleeding edge env orchestration.

Tepix2• 4 years ago

This is interesting. I hope someone will do the same to re-add PCIe 4.0 support to AMD AM4 B450 chipset mainboards (it was available temporarily until AMD took it away again in later AGESA versions). Not a trivial hack i reckon.

ilyt3• 4 years ago

It's weird considering the PCIe is wired directly to CPU anyway, why would chipset affect level of support ?

dvdkon• 4 years ago

I think the official reasoning was that the motherboards weren't made with gen 4 in mind, so signal integrity problems could arise (as they do with many gen 3 riser cables).

ilyt3• 4 years ago

I have no idea why option to disable it even exists in BIOSes, let alone is often set to default.

Anyone have insight on it ? What's the utility of being able to disable virtualization ?

Even in case of "corpo disallows it" (for whatever idiotic reason) it can be turned off one way or another in OS...

whatwherewhy• 4 years ago

Even in case of "corpo disallows it" (for whatever idiotic reason) it can be turned off one way or another in OS...

Corpo can disallow that too via central policies

adastra22• 4 years ago

Well I consider this an idiotic but pragmatic reason: I've encountered laptops where Windows Subsystem for Linux will cause windows to bluescreen on boot (do they still call it that?) when VT-x is enabled. There's an open bug report tracking the on WSL for a couple of years now.

ChuckNorris898• 4 years ago

IIRC hardware CPU virtualization enabled in BIOS could have some negative impact/bugs on some SW, and also open the SW to some security vulnerabilities so it's a good idea to give the user the option to disable it and use SW virtualization instead.

sumtechguy• 4 years ago

Another reason is market segmentation. This model has xyz, but for 50 more you can have one that does this cool thing. Even though the hardware is there. Pretty much all of the large OEM's do this. In the micro economics world it is called 'perfect pricing'. Basically segmenting your product enough and putting the prices at the right spot so everyone wants to buy along curve. In practice it is harder to do than that. So you get weird bits of hardware that can do things but are fused out. Car manufactures are trying to do this with 'rent your heated seats' kind of things. On the back end it simplifies what you buy into your pipeline and you control it with software.

rb12345• 4 years ago

It's true that Blue Pill and friends were an issue 15 years ago. I would have expected VT-x to be on by default now though given that Windows 10 and 11 both use virtualisation for various security features (Credential Guard, HVCI and so on). There's no advantage to disabling it...

(Edit: of course, that wasn't the case when this particular article and BIOS was written.)

sebow• 4 years ago

In some cases virtualization can affect performance. Mind you last time I checked this to be the case was around 2017-2018. I don't know about the situation right now (though I wouldn't be surprised if it would still apply in some workloads).

q-big• 4 years ago

What's the utility of being able to disable virtualization ?

I consider the option to disable (or rather: enable this function manually if you need it) virtualization to be quite useful because if this feature is disabled, malicious software cannot install a virtualization rootkit, i.e. a rootkit that makes itself a hypervisor and moves the current OS instance into a virtual machine running under this hypervisor.

See for example https://en.wikipedia.org/wiki/Blue_Pill_(software)

justsomehnguy• 4 years ago

Because Average Joe doesn't use virtualization at all, while Average Malicious Hacker would use it in a heartbeat if he can.

oneplane3• 4 years ago

Market segmentation to make more money (it needs to be configurable to lock if 'off'), and configurable with default 'off': older platforms and software was really bad at dealing with virtualisation. Only years after the likes of the Q35 and Q45 chipsets did it get better. It was so bad that up to a point you were better off disabling it and using paravirtualisation instead. The same happened during the Vt-d introduction btw.

userbinator4• 4 years ago

older platforms and software was really bad at dealing with virtualisation

As far as I know, it just enables a few new CPU instructions, but older software that didn't know about them wouldn't use them anyway?

comprev• 4 years ago

Needs (2012)

nivenkos3• 4 years ago

I used one of these for years for programming whilst travelling at university.

It worked well, but I could pretty much only run one program at a time. It felt more like the old microcomputers in that respect!

But that forced me to use dwm and Arch Linux, and learn a lot more in the process.

loudmax• 4 years ago

I had Compiz Fusion with LXDE running on my Acer Aspire One and I was amazed at how well it performed. Wobbly windows for live video from the webcam and everything. Running Gentoo's emerge did take all day though. In retrospect, Arch would have been a better fit.

nivenkos3• 4 years ago

I distinctly remember having to use mplayer/mpv over VLC, and youtube-dl, etc. (definitely not Chrome!) just to be able to play any reasonable video (usually downscaled from 1080p).

And Zathura for lightweight PDF reading (with customisable colours!).

And of course vim and emacs (you're not running IntelliJ, PyCharm, etc. on that).

But it worked really well, and in retrospect was probably good for productivity as you couldn't really do anything else. So I'd download Coursera videos and watch them on the train with mpv/mplayer, etc. - it was frustrating when I had to fix some GUI code on-the-go though, and could barely use Glade with the tiny resolution and screen.

flas9sd• 4 years ago

I was wondering about the contents of the site sudonull.com - seemed a mixed bag, not a tech blog. Apparently it's translated repost from habr.com - both sites serve from different networks, so I'm not sure they're legitimately affiliated, but could very well be.

https://habr.com/ru/post/152056/

https://en.wikipedia.org/wiki/Habr

u8080• 4 years ago

Habr allows reposts from different media, but only by author.

grishka• 4 years ago

The article very much looks like it's machine translated from Russian because some phrases are weird in English but make perfect sense if you translate them back. Also some screenshots are in Russian.

notjulianjaynes• 4 years ago

What a strange coincidence, I was just looking at an old Aspire ZG5 that was sitting in a box of old laptops I've been hoarding, and thought to myself that it was a cool form factor too bad it's so ridiculously underpowered to be useful for anything.

I don't think I'll be doing this, nor, as I briefly considered, trying to wedge a raspberry pi in the case. Cute machine though.

folkrav2• 4 years ago

Netbooks were pretty cool as far as form factor went, but indeed, they were mostly utterly useless, often running clocked down single-core Atom chips...

cestith• 4 years ago

I used to see a lot of them in conferences where college students or industry folks had them for note taking and had a bigger, bulkier, more powerful computer elsewhere. As a primary computer they were lacking, but as a second one they were cheap and easily mobile.

smileybarry• 4 years ago

I used an extremely weak Acer netbook — the kind that shipped with Windows XP and still slowed down — as an Ubuntu home server and it worked surprisingly well. Apt didn’t mind the small, slow hard drive and everything seemed to actually run relatively fast. (I guess it just really hated drawing a GUI?) It was mostly a printer server, serving CUPS for a USB-only printer, but it did its job well for years and years. Plus the battery had an upside of serving as a UPS, heh.

But I did learn the hard way that they’re really not meant to run like that: the fan became increasingly noisy until it sounded like a car ignition, and the heat (when the fan was working fine!) managed to slowly wear out the membrane keyboard, killing more and more keys, making in-person debugging kinda difficult.

But it was really cool. And I still have its more performant cousin Asus netbook somewhere!

egberts1• 4 years ago

Yeah, just a small off-point: some CPU support VT-d but for some reason the corresponding chipset does not (yet their BIOS offers this as a configurable item).

Looking at you, Dell BIOS and Intel i7-2700 and Intel Q65 chipset.

ridgered42• 4 years ago

Huh, I was under the impression that the Q chipsets were the ones that officially supported this.

I have a few ivybridge era chipset boards (B75, Z77) some of which actually don't officially support this feature but the motherboard manufacturers enabled it in bios anyway and it works. The sandybridge era was much messier for this feature.

It is very irritating Intel tried to gate this behind chipsets since I believe it is 100% handled by the processor.

chx• 4 years ago

This should have (2012) in the title.

Also, there's no breaking involved as there's no signature anywhere, it's a reasonably simple mod. For example, re-enabling CPU undervolting seems to be impossible in modern ThinkPads because the UEFI firmware is signed.

csdvrx• 4 years ago

Do you have more details?

Why can't you upload your own private key in the new bios payload, like you can for SecureBoot?

Everything is sitting in a flash chip. Some parts may be RO, but it can be replaced by another chip if you can't tweak it directly with flashrom.

Harvesterify• 4 years ago

I'm guessing Intel Boot Guard is enabled and provisionned with Dell keys, but it's just a guess.

treffer• 4 years ago

oh well, I thought the same, but got curious because the framework laptop would be way nicer with an open UEFI...

Vendors burn a key into the system which prevents loading an unsigned BIOS. This is a one-time-programmable fuse (OTP fuse) and part of Intel BootGuard protections.

You get a laptop with _fused burned_ to prevent loading other firmware to your device. Booting won't work if you load a replacement SPI chip with anything but a vendor-signed firmware.

anonymousiam3• 4 years ago

Reminds me of the time (in 1990) that I hacked my 386 BIOS so I could add an IDE drive. That motherboard did not allow manually specifying C/H/S (https://en.wikipedia.org/wiki/Cylinder-head-sector) and the drive was much larger than any of the presets. Initially I tried just patching the table of preset values, but my first attempt failed because the checksum had changed and the BIOS failed POST. I ended up modifying two other unused table entries to force a checksum collision.

joombaga• 4 years ago

Nice! Was it difficult to find values that would force a collision? What kind of checksumming did it use?

anonymousiam3• 4 years ago

Back in the day of 16-bit (386sx) 25MHz CPUs with no FPU, the original "Sum Complement" checksum was still more popular than CRC, BCH, or hashing functions.

https://en.wikipedia.org/wiki/Checksum#Algorithms

stevefan1999• 4 years ago

it has to be the classical crc32 and is easy cause you know it is just 32-bit :d

anonymousiam3• 4 years ago

I forgot to mention the most "exciting" part of this hack. My (UV) EPROM programmer was an ISA-based peripheral and the 386 was my only PC (with an ISA bus), so I booted it up and then removed the EPROM from the socket on the motherboard, put it into the programmer to get an image (because I did not have confidence that the copy in RAM hadn't been altered), then reversed the image and burned a new EPROM. (If I hadn't used a new EPROM, I would have rendered my computer useless with no way to revert.) Fortunately I had a UV eraser so I could give it another go when the first iteration didn't work.

Breaking BIOS: enabling VT-x virtualization support on Acer Aspire One netbook

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