f8052a053a
Move the !PRESENT and !ACCESSED checks in FNAME(prefetch_invalid_gpte) above the call to is_rsvd_bits_set(). For a well behaved guest, the !PRESENT and !ACCESSED are far more likely to evaluate true than the reserved bit checks, and they do not require additional memory accesses. Before: Dump of assembler code for function paging32_prefetch_invalid_gpte: 0x0000000000044240 <+0>: callq 0x44245 <paging32_prefetch_invalid_gpte+5> 0x0000000000044245 <+5>: mov %rcx,%rax 0x0000000000044248 <+8>: shr $0x7,%rax 0x000000000004424c <+12>: and $0x1,%eax 0x000000000004424f <+15>: lea 0x0(,%rax,4),%r8 0x0000000000044257 <+23>: add %r8,%rax 0x000000000004425a <+26>: mov %rcx,%r8 0x000000000004425d <+29>: and 0x120(%rsi,%rax,8),%r8 0x0000000000044265 <+37>: mov 0x170(%rsi),%rax 0x000000000004426c <+44>: shr %cl,%rax 0x000000000004426f <+47>: and $0x1,%eax 0x0000000000044272 <+50>: or %rax,%r8 0x0000000000044275 <+53>: jne 0x4427c <paging32_prefetch_invalid_gpte+60> 0x0000000000044277 <+55>: test $0x1,%cl 0x000000000004427a <+58>: jne 0x4428a <paging32_prefetch_invalid_gpte+74> 0x000000000004427c <+60>: mov %rdx,%rsi 0x000000000004427f <+63>: callq 0x44080 <drop_spte> 0x0000000000044284 <+68>: mov $0x1,%eax 0x0000000000044289 <+73>: retq 0x000000000004428a <+74>: xor %eax,%eax 0x000000000004428c <+76>: and $0x20,%ecx 0x000000000004428f <+79>: jne 0x44289 <paging32_prefetch_invalid_gpte+73> 0x0000000000044291 <+81>: mov %rdx,%rsi 0x0000000000044294 <+84>: callq 0x44080 <drop_spte> 0x0000000000044299 <+89>: mov $0x1,%eax 0x000000000004429e <+94>: jmp 0x44289 <paging32_prefetch_invalid_gpte+73> End of assembler dump. After: Dump of assembler code for function paging32_prefetch_invalid_gpte: 0x0000000000044240 <+0>: callq 0x44245 <paging32_prefetch_invalid_gpte+5> 0x0000000000044245 <+5>: test $0x1,%cl 0x0000000000044248 <+8>: je 0x4424f <paging32_prefetch_invalid_gpte+15> 0x000000000004424a <+10>: test $0x20,%cl 0x000000000004424d <+13>: jne 0x4425d <paging32_prefetch_invalid_gpte+29> 0x000000000004424f <+15>: mov %rdx,%rsi 0x0000000000044252 <+18>: callq 0x44080 <drop_spte> 0x0000000000044257 <+23>: mov $0x1,%eax 0x000000000004425c <+28>: retq 0x000000000004425d <+29>: mov %rcx,%rax 0x0000000000044260 <+32>: mov (%rsi),%rsi 0x0000000000044263 <+35>: shr $0x7,%rax 0x0000000000044267 <+39>: and $0x1,%eax 0x000000000004426a <+42>: lea 0x0(,%rax,4),%r8 0x0000000000044272 <+50>: add %r8,%rax 0x0000000000044275 <+53>: mov %rcx,%r8 0x0000000000044278 <+56>: and 0x120(%rsi,%rax,8),%r8 0x0000000000044280 <+64>: mov 0x170(%rsi),%rax 0x0000000000044287 <+71>: shr %cl,%rax 0x000000000004428a <+74>: and $0x1,%eax 0x000000000004428d <+77>: mov %rax,%rcx 0x0000000000044290 <+80>: xor %eax,%eax 0x0000000000044292 <+82>: or %rcx,%r8 0x0000000000044295 <+85>: je 0x4425c <paging32_prefetch_invalid_gpte+28> 0x0000000000044297 <+87>: mov %rdx,%rsi 0x000000000004429a <+90>: callq 0x44080 <drop_spte> 0x000000000004429f <+95>: mov $0x1,%eax 0x00000000000442a4 <+100>: jmp 0x4425c <paging32_prefetch_invalid_gpte+28> End of assembler dump. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.