On 2017-07-25 23:23, Gustavo Lima Chaves wrote:
> * Jan Kiszka <[email protected]> [2017-07-25 08:11:32 +0200]:
> 
> [...]
> 
>>>> +// TODO: convert to whitelist
>>>>  static u8 __attribute__((aligned(PAGE_SIZE))) msr_bitmap[][0x2000/8] = {
>>>>    [ VMX_MSR_BMP_0000_READ ] = {
>>>>            [      0/8 ...  0x7ff/8 ] = 0,
>>>> -- 
>>>> 2.1.4
>>>
>>> Just to get/align the rationale here on the MRS whitelist. The idea is to 
>>> expose the whitelist as root/inmate cell configs as well, just like the PIO 
>>> bitmap right now? If so, I wonder if having all accesses besides those 
>>> already treated denied and then working with a minimal set to have, say, a 
>>> bootable Linux inmate as a default config would be acceptable or there is 
>>> another idea... 
>>>
>>
>> The idea is to first of all try to define a static whitelist of MSRs
>> that are safe to be handed out to the guest because they do not affect
>> the integrity of the hypervisor on that same logical CPU, nor do they
>> have cross-cell effects. If working out that list requires per-board
>> configurations (maybe not unlikely), we may need to extend the config
>> format as well.
> 
> Thanks! What about MSRs that are the key/point-of-access for other
> features, like power management (changing P/C-states on x86)? So is it
> that the power management TODO entry is totally encompassed by the MSR
> one or am I missing something?

MSRs are one way to manage power on x86. mwait is another. This area
requires a careful analysis and waits with some nasty dependencies on us
(plus horrible ACPI complexity). So, MSRs access control will play a
role for it but will solve it alone.

Jan

-- 
Siemens AG, Corporate Technology, CT RDA ITP SES-DE
Corporate Competence Center Embedded Linux

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