* Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > /* Prepare to add new identity pagetables on demand. */ > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index daf8936d0628..077e8b45784c 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -273,8 +273,20 @@ return_from_SYSCALL_64: > * Change top bits to match most significant bit (47th or 56th bit > * depending on paging mode) in the address. > */ > +#ifdef CONFIG_X86_5LEVEL > + testl $1, p4d_folded(%rip) > + jnz 1f > + shl $(64 - 57), %rcx > + sar $(64 - 57), %rcx > + jmp 2f > +1: > + shl $(64 - 48), %rcx > + sar $(64 - 48), %rcx > +2: > +#else > shl $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx > sar $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx > +#endif So I really, really hate this change, as it slows down everything, not just LA57 hardware, and slows down a critical system call hot path. (I expect enterprise distros to enable CONFIG_X86_5LEVEL.) Could this use alternatives patching instead? Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
