Conversation
hyeyoo

Hyeonggon Yoo

Edited 1 year ago
started wondering where it's documented that x86 processors deal with the synonym problem, as they use VIPT data caches.

on ARMv8 processors there is an architectural guarantee that data caches acts as PIPT cache even if it's actually VIPT, so it's guaranteed not to suffer from D-cache aliasing.

I've been heard that there is a similar guarantee on x86 processors but haven't found any official references about it - errr, I guess it's time to read some part of the intel manual.

btw this is quite old but is very nice introduction:
https://www.linuxjournal.com/article/7105
1
1
1
vbabka

Vlastimil Babka

Reply to @hyeyoo
@hyeyoo do x86 really use VIPT? IIRC I've seen that mentioned only for L1, but that always had size/associativity = 4096 so that's kinda moot ;) L2+ were PIPT. Anything changed recently?
1
0
0
hyeyoo

Hyeonggon Yoo

Reply to @vbabka
@vbabka

Designing VIPT caches where size/associativity <= PAGE_SIZE is a way to avoid the synonym problem, no?

It gets tricky when size/associativity > PAGE_SIZE and it seems both Intel and ARM have patents to deal with it

https://patents.google.com/patent/US11314647B2/en
https://patents.google.com/patent/US20070033318A1/en
1
0
1
vbabka

Vlastimil Babka

Reply to @hyeyoo
@hyeyoo yeah like I've said I've only seen in avoided this way so far, dunno other approaches but presumably they are more complex.
0
0
1
About social.kernel.org

Terms of service

  1. Please do not use this service in violation of the Linux Kernel Code of Conduct. Doing so will result in your account suspension with the referral of the matter to the CoC committee.

  2. "Repeating"/"boosting" someone else's status on this platform will be treated as endorsement and will fall under rule #1.

  3. You are encouraged to use this platform to promote your work on the Linux Kernel, but there is no restriction on permitted topics (with the exception of anything covered by #1 above).

  4. There is no requirement to post in English, but it should be considered the primary language of communication on this platform.

Privacy notice

The admins of this service have access to all posted statuses. They aren't looking, but if it's something they shouldn't know about, then you should not post it on this platform.

Please see the Linux Foundation Privacy Policy, which applies to this platform as well.

Getting your own account

If you would like an account on this instance, please check that the following applies to you:

  • You are listed in MAINTAINERS or CREDITS

  • OR: You have a kernel.org account or email address

  • OR: You have a long and established history of involvement with the Linux Kernel

If the above is true and you agree with the Terms of Service and Privacy Notice listed above, please use these instructions to request an account: