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Re: [PATCH] docs: qemu-cpu-models: Document '-noTSX' variants and 'mds-n
From: |
Kashyap Chamarthy |
Subject: |
Re: [PATCH] docs: qemu-cpu-models: Document '-noTSX' variants and 'mds-no' |
Date: |
Fri, 17 Jan 2020 14:22:58 +0100 |
On Thu, Jan 16, 2020 at 06:36:38PM +0100, Kashyap Chamarthy wrote:
[...]
> (2) There are _three_ variants[+] of CascadeLake CPUs, with different
> stepping levels: 5, 6, and 7. To quite wikichip.org[*]:
s/quite/quote/
>
> "note that while steppings 6 & 7 are fully mitigated, earlier
> stepping 5 is not protected against MSBDS, MLPDS, nor MDSUM"
>
> The above is also indicated in the Intel's manual itself[+], as
> indicated by "No" under the three columns of MFBDS, MSBDS, and
> MLPDS.
>
> [+]
> https://software.intel.com/security-software-guidance/insights/processors-affected-microarchitectural-data-sampling
> [*]
> https://en.wikichip.org/wiki/intel/microarchitectures/cascade_lake#Key_changes_from_Skylake
>
> Signed-off-by: Kashyap Chamarthy <address@hidden>
> ---
> TODO:
> - I think I also need to add a note about 'tsx-ctrl' bit. Here too,
> same question as above -- does it show up in /proc/cpuinfo/?
While at it ... if I mention 'mds-no', then it would be inconsistent,
and inaccurate, if I don't also mention 'taa-no' IA32_ARCH_CAPABILITIES
MSR bit.
In short, I should mention the following MSR bits, and their use, in
context:
- mds-no
- taa-no
- tsx-ctrl
... while bearing in mind that none (?) of these MSR bits will show up
under /proc/cpuinfo in the guest, rather they're used to populate the
relevant vulnerability file in sysfs
(/sys/devices/system/cpu/vulnerabilities/).
[...]
--
/kashyap