| Message ID | 20240102015808.132373-8-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| State | Superseded |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: > Use qemu_real_host_page_size. > If the commpage is not within reserved_va, use MAP_FIXED_NOREPLACE. > > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > --- > linux-user/elfload.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/linux-user/elfload.c b/linux-user/elfload.c > index 4fcc490ce6..2e2b1b0784 100644 > --- a/linux-user/elfload.c > +++ b/linux-user/elfload.c > @@ -459,6 +459,7 @@ enum { > static bool init_guest_commpage(void) > { > ARMCPU *cpu = ARM_CPU(thread_cpu); > + int host_page_size = qemu_real_host_page_size(); > abi_ptr commpage; > void *want; > void *addr; > @@ -471,10 +472,12 @@ static bool init_guest_commpage(void) > return true; > } > > - commpage = HI_COMMPAGE & -qemu_host_page_size; > + commpage = HI_COMMPAGE & -host_page_size; > want = g2h_untagged(commpage); > - addr = mmap(want, qemu_host_page_size, PROT_READ | PROT_WRITE, > - MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); > + addr = mmap(want, host_page_size, PROT_READ | PROT_WRITE, > + MAP_ANONYMOUS | MAP_PRIVATE | > + (commpage < reserved_va ? MAP_FIXED : MAP_FIXED_NOREPLACE), > + -1, 0); > > if (addr == MAP_FAILED) { > perror("Allocating guest commpage"); > @@ -487,12 +490,12 @@ static bool init_guest_commpage(void) > /* Set kernel helper versions; rest of page is 0. */ > __put_user(5, (uint32_t *)g2h_untagged(0xffff0ffcu)); > > - if (mprotect(addr, qemu_host_page_size, PROT_READ)) { > + if (mprotect(addr, host_page_size, PROT_READ)) { > perror("Protecting guest commpage"); > exit(EXIT_FAILURE); > } > > - page_set_flags(commpage, commpage | ~qemu_host_page_mask, > + page_set_flags(commpage, commpage | (host_page_size - 1), > PAGE_READ | PAGE_EXEC | PAGE_VALID); > return true; > } To confirm if I understand correctly, when using a reserved va, the contiguous address space is reserved using mmap, thus MAP_FIXED_NOREPLACE would fail when hitting it? Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
On 1/8/24 20:38, Pierrick Bouvier wrote: > On 1/2/24 05:57, Richard Henderson wrote: >> Use qemu_real_host_page_size. >> If the commpage is not within reserved_va, use MAP_FIXED_NOREPLACE. >> >> Signed-off-by: Richard Henderson <richard.henderson@linaro.org> >> --- >> linux-user/elfload.c | 13 ++++++++----- >> 1 file changed, 8 insertions(+), 5 deletions(-) >> >> diff --git a/linux-user/elfload.c b/linux-user/elfload.c >> index 4fcc490ce6..2e2b1b0784 100644 >> --- a/linux-user/elfload.c >> +++ b/linux-user/elfload.c >> @@ -459,6 +459,7 @@ enum { >> static bool init_guest_commpage(void) >> { >> ARMCPU *cpu = ARM_CPU(thread_cpu); >> + int host_page_size = qemu_real_host_page_size(); >> abi_ptr commpage; >> void *want; >> void *addr; >> @@ -471,10 +472,12 @@ static bool init_guest_commpage(void) >> return true; >> } >> - commpage = HI_COMMPAGE & -qemu_host_page_size; >> + commpage = HI_COMMPAGE & -host_page_size; >> want = g2h_untagged(commpage); >> - addr = mmap(want, qemu_host_page_size, PROT_READ | PROT_WRITE, >> - MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); >> + addr = mmap(want, host_page_size, PROT_READ | PROT_WRITE, >> + MAP_ANONYMOUS | MAP_PRIVATE | >> + (commpage < reserved_va ? MAP_FIXED : MAP_FIXED_NOREPLACE), >> + -1, 0); >> if (addr == MAP_FAILED) { >> perror("Allocating guest commpage"); >> @@ -487,12 +490,12 @@ static bool init_guest_commpage(void) >> /* Set kernel helper versions; rest of page is 0. */ >> __put_user(5, (uint32_t *)g2h_untagged(0xffff0ffcu)); >> - if (mprotect(addr, qemu_host_page_size, PROT_READ)) { >> + if (mprotect(addr, host_page_size, PROT_READ)) { >> perror("Protecting guest commpage"); >> exit(EXIT_FAILURE); >> } >> - page_set_flags(commpage, commpage | ~qemu_host_page_mask, >> + page_set_flags(commpage, commpage | (host_page_size - 1), >> PAGE_READ | PAGE_EXEC | PAGE_VALID); >> return true; >> } > > To confirm if I understand correctly, when using a reserved va, the contiguous address > space is reserved using mmap, thus MAP_FIXED_NOREPLACE would fail when hitting it? Correct. r~
diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 4fcc490ce6..2e2b1b0784 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -459,6 +459,7 @@ enum { static bool init_guest_commpage(void) { ARMCPU *cpu = ARM_CPU(thread_cpu); + int host_page_size = qemu_real_host_page_size(); abi_ptr commpage; void *want; void *addr; @@ -471,10 +472,12 @@ static bool init_guest_commpage(void) return true; } - commpage = HI_COMMPAGE & -qemu_host_page_size; + commpage = HI_COMMPAGE & -host_page_size; want = g2h_untagged(commpage); - addr = mmap(want, qemu_host_page_size, PROT_READ | PROT_WRITE, - MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); + addr = mmap(want, host_page_size, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE | + (commpage < reserved_va ? MAP_FIXED : MAP_FIXED_NOREPLACE), + -1, 0); if (addr == MAP_FAILED) { perror("Allocating guest commpage"); @@ -487,12 +490,12 @@ static bool init_guest_commpage(void) /* Set kernel helper versions; rest of page is 0. */ __put_user(5, (uint32_t *)g2h_untagged(0xffff0ffcu)); - if (mprotect(addr, qemu_host_page_size, PROT_READ)) { + if (mprotect(addr, host_page_size, PROT_READ)) { perror("Protecting guest commpage"); exit(EXIT_FAILURE); } - page_set_flags(commpage, commpage | ~qemu_host_page_mask, + page_set_flags(commpage, commpage | (host_page_size - 1), PAGE_READ | PAGE_EXEC | PAGE_VALID); return true; }
Use qemu_real_host_page_size. If the commpage is not within reserved_va, use MAP_FIXED_NOREPLACE. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- linux-user/elfload.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)