| Message ID | 20240102015808.132373-6-richard.henderson@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | linux-user: Improve host and guest page size handling | expand |
On 1/2/24 05:57, Richard Henderson wrote: > If reserved_va, then we have already reserved the entire > guest virtual address space; no need to remap page. > If !reserved_va, then use MAP_FIXED_NOREPLACE. > > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > --- > linux-user/elfload.c | 23 ++++++++++++++--------- > 1 file changed, 14 insertions(+), 9 deletions(-) > > diff --git a/linux-user/elfload.c b/linux-user/elfload.c > index c166faabab..96d8d4f84c 100644 > --- a/linux-user/elfload.c > +++ b/linux-user/elfload.c > @@ -1969,16 +1969,21 @@ static inline void init_thread(struct target_pt_regs *regs, > > static bool init_guest_commpage(void) > { > - void *want = g2h_untagged(LO_COMMPAGE); > - void *addr = mmap(want, qemu_host_page_size, PROT_NONE, > - MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); > + /* If reserved_va, then we have already mapped 0 page on the host. */ > + if (!reserved_va) { > + int host_page_size = qemu_real_host_page_size(); > + void *want, *addr; > > - if (addr == MAP_FAILED) { > - perror("Allocating guest commpage"); > - exit(EXIT_FAILURE); > - } > - if (addr != want) { > - return false; > + want = g2h_untagged(LO_COMMPAGE); > + addr = mmap(want, host_page_size, PROT_NONE, > + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED_NOREPLACE, -1, 0); > + if (addr == MAP_FAILED) { > + perror("Allocating guest commpage"); > + exit(EXIT_FAILURE); > + } > + if (addr != want) { > + return false; > + } > } > > /* Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
On Tue, Jan 02, 2024 at 12:57:40PM +1100, Richard Henderson wrote: > If reserved_va, then we have already reserved the entire > guest virtual address space; no need to remap page. > If !reserved_va, then use MAP_FIXED_NOREPLACE. > > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > --- > linux-user/elfload.c | 23 ++++++++++++++--------- > 1 file changed, 14 insertions(+), 9 deletions(-) > > diff --git a/linux-user/elfload.c b/linux-user/elfload.c > index c166faabab..96d8d4f84c 100644 > --- a/linux-user/elfload.c > +++ b/linux-user/elfload.c > @@ -1969,16 +1969,21 @@ static inline void init_thread(struct target_pt_regs *regs, > > static bool init_guest_commpage(void) > { > - void *want = g2h_untagged(LO_COMMPAGE); > - void *addr = mmap(want, qemu_host_page_size, PROT_NONE, > - MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); > + /* If reserved_va, then we have already mapped 0 page on the host. */ > + if (!reserved_va) { > + int host_page_size = qemu_real_host_page_size(); > + void *want, *addr; > > - if (addr == MAP_FAILED) { > - perror("Allocating guest commpage"); > - exit(EXIT_FAILURE); > - } > - if (addr != want) { > - return false; > + want = g2h_untagged(LO_COMMPAGE); > + addr = mmap(want, host_page_size, PROT_NONE, > + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED_NOREPLACE, -1, 0); > + if (addr == MAP_FAILED) { > + perror("Allocating guest commpage"); > + exit(EXIT_FAILURE); > + } > + if (addr != want) { > + return false; > + } > } > > /* > -- > 2.34.1 Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
On Mon, Jan 29, 2024 at 11:28:59AM +0100, Ilya Leoshkevich wrote: > On Tue, Jan 02, 2024 at 12:57:40PM +1100, Richard Henderson wrote: > > If reserved_va, then we have already reserved the entire > > guest virtual address space; no need to remap page. > > If !reserved_va, then use MAP_FIXED_NOREPLACE. > > > > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > > --- > > linux-user/elfload.c | 23 ++++++++++++++--------- > > 1 file changed, 14 insertions(+), 9 deletions(-) > > > > diff --git a/linux-user/elfload.c b/linux-user/elfload.c > > index c166faabab..96d8d4f84c 100644 > > --- a/linux-user/elfload.c > > +++ b/linux-user/elfload.c > > @@ -1969,16 +1969,21 @@ static inline void init_thread(struct target_pt_regs *regs, > > > > static bool init_guest_commpage(void) > > { > > - void *want = g2h_untagged(LO_COMMPAGE); > > - void *addr = mmap(want, qemu_host_page_size, PROT_NONE, > > - MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); > > + /* If reserved_va, then we have already mapped 0 page on the host. */ > > + if (!reserved_va) { > > + int host_page_size = qemu_real_host_page_size(); > > + void *want, *addr; > > > > - if (addr == MAP_FAILED) { > > - perror("Allocating guest commpage"); > > - exit(EXIT_FAILURE); > > - } > > - if (addr != want) { > > - return false; > > + want = g2h_untagged(LO_COMMPAGE); > > + addr = mmap(want, host_page_size, PROT_NONE, > > + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED_NOREPLACE, -1, 0); One question though: if TARGET_PAGE_SIZE > host_page_size, things would work, because the magic offsets are quite small. But wouldn't it be overall cleaner to map TARGET_PAGE_SIZE bytes, just to be closer to the real thing?
diff --git a/linux-user/elfload.c b/linux-user/elfload.c index c166faabab..96d8d4f84c 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -1969,16 +1969,21 @@ static inline void init_thread(struct target_pt_regs *regs, static bool init_guest_commpage(void) { - void *want = g2h_untagged(LO_COMMPAGE); - void *addr = mmap(want, qemu_host_page_size, PROT_NONE, - MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); + /* If reserved_va, then we have already mapped 0 page on the host. */ + if (!reserved_va) { + int host_page_size = qemu_real_host_page_size(); + void *want, *addr; - if (addr == MAP_FAILED) { - perror("Allocating guest commpage"); - exit(EXIT_FAILURE); - } - if (addr != want) { - return false; + want = g2h_untagged(LO_COMMPAGE); + addr = mmap(want, host_page_size, PROT_NONE, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED_NOREPLACE, -1, 0); + if (addr == MAP_FAILED) { + perror("Allocating guest commpage"); + exit(EXIT_FAILURE); + } + if (addr != want) { + return false; + } } /*
If reserved_va, then we have already reserved the entire guest virtual address space; no need to remap page. If !reserved_va, then use MAP_FIXED_NOREPLACE. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- linux-user/elfload.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-)