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. 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 <i...@linux.ibm.com> Message-Id: <20220725125043.43048-1-...@linux.ibm.com> --- accel/tcg/translate-all.c | 2 +- include/exec/cpu-all.h | 6 ++++++ linux-user/mmap.c | 27 ++++++++++++++++++++++----- 3 files changed, 29 insertions(+), 6 deletions(-) diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c index b83161a081..a47cf38e38 100644 --- a/accel/tcg/translate-all.c +++ b/accel/tcg/translate-all.c @@ -2263,7 +2263,7 @@ 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 diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h index 491629b9ba..16b7df41bf 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 0x0800 + #if defined(CONFIG_USER_ONLY) void page_dump(FILE *f); diff --git a/linux-user/mmap.c b/linux-user/mmap.c index a5f1ab129c..3a0f67619a 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -425,7 +425,8 @@ 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(); @@ -538,6 +539,8 @@ 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; @@ -620,6 +623,8 @@ 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: @@ -627,7 +632,18 @@ 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)) { @@ -846,7 +862,7 @@ 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; } } @@ -888,8 +904,9 @@ 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 && -- 2.37.2