Messages in this thread | | | Date | Tue, 28 Nov 2023 16:00:04 +0800 | Subject | Re: [PATCH v7 04/26] x86/fpu/xstate: Introduce XFEATURE_MASK_KERNEL_DYNAMIC xfeature set | From | "Yang, Weijiang" <> |
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On 11/28/2023 9:46 AM, Edgecombe, Rick P wrote: > On Fri, 2023-11-24 at 00:53 -0500, Yang Weijiang wrote: >> Define new XFEATURE_MASK_KERNEL_DYNAMIC set including the features >> can be >> optionally enabled by kernel components, i.e., the features are >> required by >> specific kernel components. > The above is a bit tough to parse. Does any of this seem clearer? > > Define a new XFEATURE_MASK_KERNEL_DYNAMIC mask to specify the features > that can be optionally enabled by kernel components. This is similar to > XFEATURE_MASK_KERNEL_DYNAMIC in that it contains optional xfeatures > that can allows the FPU buffer to be dynamically sized. The difference > is that the KERNEL variant contains supervisor features and will be > enabled by kernel components that need them, and not directly by the > user.
Definitely the wording is much better, I'll apply it to next version, thanks a lot!
>> Currently it's used by KVM to configure guest >> dedicated fpstate for calculating the xfeature and fpstate storage >> size etc. >> >> The kernel dynamic xfeatures now only contain XFEATURE_CET_KERNEL, >> which is >> supported by host as they're enabled in xsaves/xrstors operating >> xfeature set >> (XCR0 | XSS), but the relevant CPU feature, i.e., supervisor shadow >> stack, is >> not enabled in host kernel so it can be omitted for normal fpstate by >> default. >> >> Remove the kernel dynamic feature from >> fpu_kernel_cfg.default_features so that >> the bits in xstate_bv and xcomp_bv are cleared and xsaves/xrstors can >> be >> optimized by HW for normal fpstate. > Thanks for breaking these into small patches.
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