xemu-project/xemu
1
0
Fork 0
mirror of https://github.com/xemu-project/xemu.git synced 2024-11-23 11:39:53 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

linux-user: Passthrough MADV_DONTNEED for certain file mappings

Browse Source 
This is a follow-up for commit 892a4f6a75 ("linux-user: Add partial
support for MADV_DONTNEED"), which added passthrough for anonymous
mappings. File mappings can be handled in a similar manner.

In order to do that, mark pages, for which mmap() was passed through,
with PAGE_PASSTHROUGH, and then allow madvise() passthrough for these
pages. Drop the explicit PAGE_ANON check, since anonymous mappings are
expected to have PAGE_PASSTHROUGH anyway.

Add PAGE_PASSTHROUGH to PAGE_STICKY in order to keep it on mprotect().

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220725125043.43048-1-iii@linux.ibm.com>
Message-Id: <20220906000839.1672934-5-iii@linux.ibm.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Ilya Leoshkevich 2022-09-06 02:08:38 +02:00 committed by Laurent Vivier
parent 375ce49be2
commit f93b76958a
3 changed files with 29 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
accel/tcg/translate-all.c
View File

@ -2258,7 +2258,7 @@ int page_get_flags(target_ulong address)
#ifndef PAGE_TARGET_STICKY
#define PAGE_TARGET_STICKY 0
#endif
#define PAGE_STICKY (PAGE_ANON | PAGE_TARGET_STICKY)
#define PAGE_STICKY (PAGE_ANON | PAGE_PASSTHROUGH | PAGE_TARGET_STICKY)
/* Modify the flags of a page and invalidate the code if necessary.
The flag PAGE_WRITE_ORG is positioned automatically depending

6
include/exec/cpu-all.h
View File

@ -262,6 +262,12 @@ extern const TargetPageBits target_page;
#define PAGE_TARGET_1 0x0200
#define PAGE_TARGET_2 0x0400
/*
* For linux-user, indicates that the page is mapped with the same semantics
* in both guest and host.
*/
#define PAGE_PASSTHROUGH 0x0800
#if defined(CONFIG_USER_ONLY)
void page_dump(FILE *f);

27
linux-user/mmap.c
View File

@ -431,7 +431,8 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, abi_ulong align)
abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
int flags, int fd, abi_ulong offset)
{
abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;
abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len,
passthrough_start = -1, passthrough_end = -1;
int page_flags, host_prot;
mmap_lock();
@ -544,6 +545,8 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
host_start += offset - host_offset;
}
start = h2g(host_start);
passthrough_start = start;
passthrough_end = start + len;
} else {
if (start & ~TARGET_PAGE_MASK) {
errno = EINVAL;
@ -626,6 +629,8 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
host_prot, flags, fd, offset1);
if (p == MAP_FAILED)
goto fail;
passthrough_start = real_start;
passthrough_end = real_end;
}
}
the_end1:
@ -633,7 +638,18 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
page_flags |= PAGE_ANON;
}
page_flags |= PAGE_RESET;
page_set_flags(start, start + len, page_flags);
if (passthrough_start == passthrough_end) {
page_set_flags(start, start + len, page_flags);
} else {
if (start < passthrough_start) {
page_set_flags(start, passthrough_start, page_flags);
}
page_set_flags(passthrough_start, passthrough_end,
page_flags | PAGE_PASSTHROUGH);
if (passthrough_end < start + len) {
page_set_flags(passthrough_end, start + len, page_flags);
}
}
the_end:
trace_target_mmap_complete(start);
if (qemu_loglevel_mask(CPU_LOG_PAGE)) {
@ -852,7 +868,7 @@ static bool can_passthrough_madv_dontneed(abi_ulong start, abi_ulong end)
}
for (addr = start; addr < end; addr += TARGET_PAGE_SIZE) {
if (!(page_get_flags(addr) & PAGE_ANON)) {
if (!(page_get_flags(addr) & PAGE_PASSTHROUGH)) {
return false;
}
}
@ -894,8 +910,9 @@ abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice)
* This is a hint, so ignoring and returning success is ok.
*
* This breaks MADV_DONTNEED, completely implementing which is quite
* complicated. However, there is one low-hanging fruit: host-page-aligned
* anonymous mappings. In this case passthrough is safe, so do it.
* complicated. However, there is one low-hanging fruit: mappings that are
* known to have the same semantics in the host and the guest. In this case
* passthrough is safe, so do it.
*/
mmap_lock();
if (advice == TARGET_MADV_DONTNEED &&