On 01/09/2017 12:37 AM, [email protected] wrote: > Hi Corey, > > The original intention of the 'aggressive' check was to somewhat prevent > your case where the user has set the size higher than required and may > be inadvertently be wasting memory by having the TCBBits end up larger > than needed. I agree that it can be a little inconvenient, so will > change it allow sizes that are larger, but emit a warning. >
Sounds great, thanks! > Comparing against ebx instead of ecx is quite deliberate as this way we > only measure the size required for the features that the user actually > wanted to use as defined in CONFIG_XSAVE_FEATURE_SET. This is why we do > this check just after performing 'write_xcr0' with said desired features. > Hm, this isn't consistent with my observations of the actual behavior, although I'm not seeing why at this point. On my Ivy Bridge Xeon CPU (supports AVX) with CONFIG_XSAVE_FEATURE_SET=3, using Qemu/KVM with -cpu host and the linked kernel config (and a small patch to always print out ebx/ecx), I get 576 for ebx and 832 for ecx. Kernel config: http://ix.io/1PCY My only patch from 4.0.0: http://ix.io/1PCZ Kernel log: http://ix.io/1PD3 Qemu invocation: > qemu-system-x86_64 -cpu host,+avx -enable-kvm -nographic -kernel > ~/proj/robigalia/sel4/stage/kernel-x86_64-pc99 -initrd > ~/proj/robigalia/hello-world/target/x86_64-sel4-robigalia/release/hello-world Maybe there's another issue at play here? -- cmr http://octayn.net/ +16038524272
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