This is a follow-up for commit 892a4f6a750a ("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 as well.
Signed-off-by: Ilya Leoshkevich <i...@linux.ibm.com>
---
include/exec/cpu-all.h | 6 ++++++
linux-user/mmap.c | 25 +++++++++++++++++++++----
2 files changed, 27 insertions(+), 4 deletions(-)
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index f5bda2c3ca..fbdbc0fdec 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -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 0x0080
+
#if defined(CONFIG_USER_ONLY)
void page_dump(FILE *f);
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 4e7a6be6ee..58622a0c15 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -424,7 +424,8 @@ 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();
@@ -537,6 +538,8 @@ 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;
@@ -619,6 +622,8 @@ 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:
@@ -626,7 +631,18 @@ 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)) {
@@ -845,7 +861,7 @@ 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_ANON | PAGE_PASSTHROUGH))) {
return false;
}
}
@@ -888,7 +904,8 @@ abi_long target_madvise(abi_ulong start, abi_ulong len_in,
int advice)
*
* 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.
+ * anonymous mappings or 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 & MADV_DONTNEED) &&
--
2.35.3
