linux-user: Speed up guest space initialization on 32-bit ARM target

[Qemu-devel] [PATCH 09/10] linux-user: init_guest_space: Add a comment about search strategy

Posted by Luke Shumaker 7 years, 10 months ago

From: Luke Shumaker <lukeshu@parabola.nu>

Signed-off-by: Luke Shumaker <lukeshu@parabola.nu>
---
 linux-user/elfload.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 1b7583d659..7736ea2c3a 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1936,6 +1936,10 @@ unsigned long init_guest_space(unsigned long host_start,
          * happen often.  Probably means we got unlucky and host
          * address space randomization put a shared library somewhere
          * inconvenient.
+         *
+         * This is probably a good strategy if host_start, but is
+         * probably a bad strategy if not, which means we got here
+         * because of trouble with ARM commpage setup.
          */
         munmap((void *)real_start, real_size);
         current_start += qemu_host_page_size;
-- 
2.15.1

Re: [Qemu-devel] [PATCH 09/10] linux-user: init_guest_space: Add a comment about search strategy

Posted by Peter Maydell 7 years, 7 months ago

On 28 December 2017 at 18:08, Luke Shumaker <lukeshu@lukeshu.com> wrote:
> From: Luke Shumaker <lukeshu@parabola.nu>
>
> Signed-off-by: Luke Shumaker <lukeshu@parabola.nu>
> ---
>  linux-user/elfload.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 1b7583d659..7736ea2c3a 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -1936,6 +1936,10 @@ unsigned long init_guest_space(unsigned long host_start,
>           * happen often.  Probably means we got unlucky and host
>           * address space randomization put a shared library somewhere
>           * inconvenient.
> +         *
> +         * This is probably a good strategy if host_start, but is
> +         * probably a bad strategy if not, which means we got here
> +         * because of trouble with ARM commpage setup.
>           */
>          munmap((void *)real_start, real_size);
>          current_start += qemu_host_page_size;
> --
> 2.15.1

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM

Re: [Qemu-devel] [PATCH 09/10] linux-user: init_guest_space: Add a comment about search strategy

Posted by Laurent Vivier 7 years, 7 months ago

Le 28/12/2017 à 19:08, Luke Shumaker a écrit :
> From: Luke Shumaker <lukeshu@parabola.nu>
> 
> Signed-off-by: Luke Shumaker <lukeshu@parabola.nu>
> ---
>  linux-user/elfload.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 1b7583d659..7736ea2c3a 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -1936,6 +1936,10 @@ unsigned long init_guest_space(unsigned long host_start,
>           * happen often.  Probably means we got unlucky and host
>           * address space randomization put a shared library somewhere
>           * inconvenient.
> +         *
> +         * This is probably a good strategy if host_start, but is
> +         * probably a bad strategy if not, which means we got here
> +         * because of trouble with ARM commpage setup.
>           */
>          munmap((void *)real_start, real_size);
>          current_start += qemu_host_page_size;
> 

Applied to my 'linux-user-for-2.12' branch.

Thanks,
Laurent