Re: [PATCH v6 7/8] execmem: add support for cache of large ROX pages
Luis Chamberlain <[email protected]>
| Newsgroups | gmane.linux.ports.ppc64.devel,gmane.linux.kernel.bpf,gmane.linux.ports.alpha,gmane.linux.kernel.cross-arch,gmane.linux.ports.arm.kernel,gmane.linux.ports.hexagon,gmane.linux.kernel,gmane.linux.ports.mips,gmane.linux.kernel.mm,gmane.linux.kernel.modules,gmane.linux.ports.parisc,gmane.linux.ports.riscv,gmane.linux.ports.sh.devel,gmane.linux.kernel.arc,gmane.linux.uml.devel,gmane.linux.ports.sparc |
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| Message-ID | <[email protected]> |
On Wed, Oct 16, 2024 at 03:24:23PM +0300, Mike Rapoport wrote: > From: "Mike Rapoport (Microsoft)" <[email protected]> > > Using large pages to map text areas reduces iTLB pressure and improves > performance. > > Extend execmem_alloc() with an ability to use huge pages with ROX > permissions as a cache for smaller allocations. > > To populate the cache, a writable large page is allocated from vmalloc with > VM_ALLOW_HUGE_VMAP, filled with invalid instructions and then remapped as > ROX. > > The direct map alias of that large page is exculded from the direct map. > > Portions of that large page are handed out to execmem_alloc() callers > without any changes to the permissions. > > When the memory is freed with execmem_free() it is invalidated again so > that it won't contain stale instructions. > > An architecture has to implement execmem_fill_trapping_insns() callback > and select ARCH_HAS_EXECMEM_ROX configuration option to be able to use > the ROX cache. > > The cache is enabled on per-range basis when an architecture sets > EXECMEM_ROX_CACHE flag in definition of an execmem_range. > > Signed-off-by: Mike Rapoport (Microsoft) <[email protected]> Reviewed-by: Luis Chamberlain <[email protected]> Luis