mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/
synced 2026-10-14 05:55:17 +00:00
No description
- C 96.9%
- Assembly 0.9%
- Rust 0.6%
- Shell 0.6%
- Python 0.5%
- Other 0.3%
8f8f52a45d
Use a basic NOT+AND sequence to clear the Accessed bit in TDP MMU SPTEs, as opposed to the fancy ffs()+clear_bit() logic that was copied from the legacy MMU. The legacy MMU uses clear_bit() because it is operating on the SPTE itself, i.e. clearing needs to be atomic. The TDP MMU operates on a local variable that it later writes to the SPTE, and so doesn't need to be atomic or even resident in memory. Opportunistically drop unnecessary initialization of new_spte, it's guaranteed to be written before being accessed. Using NOT+AND instead of ffs()+clear_bit() reduces the sequence from: 0x0000000000058be6 <+134>: test %rax,%rax 0x0000000000058be9 <+137>: je 0x58bf4 <age_gfn_range+148> 0x0000000000058beb <+139>: test %rax,%rdi 0x0000000000058bee <+142>: je 0x58cdc <age_gfn_range+380> 0x0000000000058bf4 <+148>: mov %rdi,0x8(%rsp) 0x0000000000058bf9 <+153>: mov $0xffffffff,%edx 0x0000000000058bfe <+158>: bsf %eax,%edx 0x0000000000058c01 <+161>: movslq %edx,%rdx 0x0000000000058c04 <+164>: lock btr %rdx,0x8(%rsp) 0x0000000000058c0b <+171>: mov 0x8(%rsp),%r15 to: 0x0000000000058bdd <+125>: test %rax,%rax 0x0000000000058be0 <+128>: je 0x58beb <age_gfn_range+139> 0x0000000000058be2 <+130>: test %rax,%r8 0x0000000000058be5 <+133>: je 0x58cc0 <age_gfn_range+352> 0x0000000000058beb <+139>: not %rax 0x0000000000058bee <+142>: and %r8,%rax 0x0000000000058bf1 <+145>: mov %rax,%r15 thus eliminating several memory accesses, including a locked access. Cc: Ben Gardon <bgardon@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20210331004942.2444916-3-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
History
|
|
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.