| Message ID | 20220725125043.43048-1-iii@linux.ibm.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] linux-user: Passthrough MADV_DONTNEED for certain file mappings | expand |
On Mon, 2022-07-25 at 14:50 +0200, Ilya Leoshkevich wrote: > 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 <iii@linux.ibm.com> > --- > > v1: > https://lists.gnu.org/archive/html/qemu-devel/2022-07/msg00112.html > v1 -> v2: Fix PAGE_PASSTHROUGH value; make checks consistent with > page_set_flags() (Laurent). > > 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..2d29ba13c0 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 4e7a6be6ee..79928e3ae5 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) && Hi, I know it's quite late, but since you are going to take the aarch64 MADV_DONTNEED patch, would it be reasonable to take this one as well? Best regards, Ilya
On Mon, 2022-07-25 at 14:50 +0200, Ilya Leoshkevich wrote: > 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 <iii@linux.ibm.com> > --- > > v1: > https://lists.gnu.org/archive/html/qemu-devel/2022-07/msg00112.html > v1 -> v2: Fix PAGE_PASSTHROUGH value; make checks consistent with > page_set_flags() (Laurent). > > 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..2d29ba13c0 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 4e7a6be6ee..79928e3ae5 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) && I would like to ping this patch and two others that I used for debugging it: [PATCH] linux-user: Fix stracing in-memory mmap arguments https://patchew.org/QEMU/20220630165901.2459135-1-iii@linux.ibm.com/ [PATCH] linux-user: Implement stracing madvise() https://patchew.org/QEMU/20220725134440.172892-1-iii@linux.ibm.com/ [PATCH v2] linux-user: Passthrough MADV_DONTNEED for certain file mappings https://patchew.org/QEMU/20220725125043.43048-1-iii@linux.ibm.com/
On 9/1/22 09:45, Ilya Leoshkevich wrote: >> +/* >> + * For linux-user, indicates that the page is mapped with the same >> semantics >> + * in both guest and host. >> + */ >> +#define PAGE_PASSTHROUGH 0x0800 I would expect a change to PAGE_STICKY in accel/tcg/translate-all.c, so that this bit is preserved across mprotect. Yes? >> @@ -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))) { Do you want both PAGE_ANON and PAGE_PASSTHROUGH? If not, is PAGE_PASSTHOUGH is sufficient by itself, why check PAGE_ANON? > I would like to ping this patch and two others that I used for > debugging it: > > [PATCH] linux-user: Fix stracing in-memory mmap arguments > https://patchew.org/QEMU/20220630165901.2459135-1-iii@linux.ibm.com/ Queued to linux-user-next. > [PATCH] linux-user: Implement stracing madvise() > https://patchew.org/QEMU/20220725134440.172892-1-iii@linux.ibm.com/ There are many more MADV_* than just the 5 you list. r~
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h index f5bda2c3ca..2d29ba13c0 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 4e7a6be6ee..79928e3ae5 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) &&
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 <iii@linux.ibm.com> --- v1: https://lists.gnu.org/archive/html/qemu-devel/2022-07/msg00112.html v1 -> v2: Fix PAGE_PASSTHROUGH value; make checks consistent with page_set_flags() (Laurent). include/exec/cpu-all.h | 6 ++++++ linux-user/mmap.c | 25 +++++++++++++++++++++---- 2 files changed, 27 insertions(+), 4 deletions(-)