Messages in this thread | | | Date | Wed, 18 Aug 2021 18:21:11 -0700 | From | "Andy Lutomirski" <> | Subject | Re: [PATCH v9 12/26] x86/fpu/xstate: Use feature disable (XFD) to protect dynamic user state |
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On Wed, Aug 18, 2021, at 2:04 PM, Thiago Macieira wrote: > On Wednesday, 18 August 2021 13:43:50 PDT Bae, Chang Seok wrote: > > > Then our API needs improving. An app should be able to ask the kernel > > > "Do you support AMX?" get a proper answer and act accordingly. > > > > Maybe I’m missing something, but I wonder what’s the difference from > > reading XCR0. > > That assumes the kernel will always enable the bits in XCR0, like it is doing > today and with your patch, because modifying it is a VM exit. > > But it's not the only possible solution. A future kernel could decide to leave > some bits off and only enable upon request. That's how macOS/Darwin does its > AVX512 support.
The fact that Darwin does this strongly suggests that real programs can handle it, which increases my inclination for Linux to do the same thing.
> > -- > Thiago Macieira - thiago.macieira (AT) intel.com > Software Architect - Intel DPG Cloud Engineering > > > >
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