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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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b16529004f
The current fpu_copy() code on lazy switching CPUs always saves into the current fpstate and then copies it over into the child context: preempt_disable(); if (!copy_fpregs_to_fpstate(src_fpu)) fpregs_deactivate(src_fpu); preempt_enable(); memcpy(&dst_fpu->state, &src_fpu->state, xstate_size); That memcpy() can be avoided on all lazy switching setups except really old FNSAVE-only systems: change fpu_copy() to directly save into the child context, for both the lazy and the eager context switching case. Note that we still have to do a memcpy() back into the parent context in the FNSAVE case, but this won't be executed on the majority of x86 systems that got built in the last 10 years or so. Reviewed-by: Borislav Petkov <bp@alien8.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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