x86/fpu: Provide infrastructure for KVM FPU cleanup
mainline inclusion from mainline-v5.16-rc1 commit 69f6ed1d category: feature bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I590ZC CVE: NA Intel-SIG: commit 69f6ed1d x86/fpu: Provide infrastructure for KVM FPU cleanup. -------------------------------- For the upcoming AMX support it's necessary to do a proper integration with KVM. Currently KVM allocates two FPU structs which are used for saving the user state of the vCPU thread and restoring the guest state when entering vcpu_run() and doing the reverse operation before leaving vcpu_run(). With the new fpstate mechanism this can be reduced to one extra buffer by swapping the fpstate pointer in current::thread::fpu. This makes the upcoming support for AMX and XFD simpler because then fpstate information (features, sizes, xfd) are always consistent and it does not require any nasty workarounds. Provide: - An allocator which initializes the state properly - A replacement for the existing FPU swap mechanim Aside of the reduced memory footprint, this also makes state switching more efficient when TIF_FPU_NEED_LOAD is set. It does not require a memcpy as the state is already correct in the to be swapped out fpstate. The existing interfaces will be removed once KVM is converted over. Signed-off-by: NThomas Gleixner <tglx@linutronix.de> Signed-off-by: NBorislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211022185312.954684740@linutronix.deSigned-off-by: NLin Wang <lin.x.wang@intel.com> Signed-off-by: NAichun Shi <aichun.shi@intel.com>
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