mii/qemu
1
0
Fork 0
mirror of https://github.com/mii443/qemu.git synced 2025-08-22 15:15:46 +00:00
Code Issues Packages Projects Releases Wiki Activity

linux-user: Add partial support for MADV_DONTNEED

Browse Source 
Currently QEMU ignores madvise(MADV_DONTNEED), which break apps that
rely on this for zeroing out memory [1]. Improve the situation by doing
a passthrough when the range in question is a host-page-aligned
anonymous mapping.

This is based on the patches from Simon Hausmann [2] and Chris Fallin
[3]. The structure is taken from Simon's patch. The PAGE_MAP_ANONYMOUS
bits are superseded by commit 26bab757d4 ("linux-user: Introduce
PAGE_ANON"). In the end the patch acts like the one from Chris: we
either pass-through the entire syscall, or do nothing, since doing this
only partially would not help the affected applications much. Finally,
add some extra checks to match the behavior of the Linux kernel [4].

[1] https://gitlab.com/qemu-project/qemu/-/issues/326
[2] https://patchew.org/QEMU/20180827084037.25316-1-simon.hausmann@qt.io/
[3] https://github.com/bytecodealliance/wasmtime/blob/v0.37.0/ci/qemu-madvise.patch
[4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/madvise.c?h=v5.19-rc3#n1368

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20220621144205.158452-1-iii@linux.ibm.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Ilya Leoshkevich
2022-06-21 16:42:05 +02:00
committed by Laurent Vivier
parent 9263ba8473
commit 892a4f6a75
4 changed files with 68 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
linux-user/user-mmap.h
View File

@ -25,6 +25,7 @@ int target_munmap(abi_ulong start, abi_ulong len);
abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
abi_ulong new_size, unsigned long flags,
abi_ulong new_addr);
abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice);
extern unsigned long last_brk;
extern abi_ulong mmap_next_start;
abi_ulong mmap_find_vma(abi_ulong, abi_ulong, abi_ulong);