[v3] linux-user: Improve host and guest page size handling

[PATCH v3 33/33] target/alpha: Enable TARGET_PAGE_BITS_VARY for user-only

Posted by Richard Henderson 10 months, 4 weeks ago

Since alpha binaries are generally built for multiple
page sizes, it is trivial to allow the page size to vary.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/alpha/cpu-param.h | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/target/alpha/cpu-param.h b/target/alpha/cpu-param.h
index 68c46f7998..c969cb016b 100644
--- a/target/alpha/cpu-param.h
+++ b/target/alpha/cpu-param.h
@@ -9,10 +9,22 @@
 #define ALPHA_CPU_PARAM_H
 
 #define TARGET_LONG_BITS 64
-#define TARGET_PAGE_BITS 13
 
 /* ??? EV4 has 34 phys addr bits, EV5 has 40, EV6 has 44.  */
 #define TARGET_PHYS_ADDR_SPACE_BITS  44
-#define TARGET_VIRT_ADDR_SPACE_BITS  (30 + TARGET_PAGE_BITS)
+
+#ifdef CONFIG_USER_ONLY
+/*
+ * Allow user-only to vary page size.  Real hardware allows only 8k and 64k,
+ * but since any variance means guests cannot assume a fixed value, allow
+ * a 4k minimum to match x86 host, which can minimize emulation issues.
+ */
+# define TARGET_PAGE_BITS_VARY
+# define TARGET_PAGE_BITS_MIN 12
+# define TARGET_VIRT_ADDR_SPACE_BITS  63
+#else
+# define TARGET_PAGE_BITS 13
+# define TARGET_VIRT_ADDR_SPACE_BITS  (30 + TARGET_PAGE_BITS)
+#endif
 
 #endif
-- 
2.34.1

Re: [PATCH v3 33/33] target/alpha: Enable TARGET_PAGE_BITS_VARY for user-only

Posted by Ilya Leoshkevich 10 months ago

On Tue, Jan 02, 2024 at 12:58:08PM +1100, Richard Henderson wrote:
> Since alpha binaries are generally built for multiple
> page sizes, it is trivial to allow the page size to vary.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/alpha/cpu-param.h | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)

Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>

Re: [PATCH v3 33/33] target/alpha: Enable TARGET_PAGE_BITS_VARY for user-only

Posted by Pierrick Bouvier 10 months, 3 weeks ago

On 1/2/24 05:58, Richard Henderson wrote:
> Since alpha binaries are generally built for multiple
> page sizes, it is trivial to allow the page size to vary.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   target/alpha/cpu-param.h | 16 ++++++++++++++--
>   1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/target/alpha/cpu-param.h b/target/alpha/cpu-param.h
> index 68c46f7998..c969cb016b 100644
> --- a/target/alpha/cpu-param.h
> +++ b/target/alpha/cpu-param.h
> @@ -9,10 +9,22 @@
>   #define ALPHA_CPU_PARAM_H
>   
>   #define TARGET_LONG_BITS 64
> -#define TARGET_PAGE_BITS 13
>   
>   /* ??? EV4 has 34 phys addr bits, EV5 has 40, EV6 has 44.  */
>   #define TARGET_PHYS_ADDR_SPACE_BITS  44
> -#define TARGET_VIRT_ADDR_SPACE_BITS  (30 + TARGET_PAGE_BITS)
> +
> +#ifdef CONFIG_USER_ONLY
> +/*
> + * Allow user-only to vary page size.  Real hardware allows only 8k and 64k,
> + * but since any variance means guests cannot assume a fixed value, allow
> + * a 4k minimum to match x86 host, which can minimize emulation issues.
> + */
> +# define TARGET_PAGE_BITS_VARY
> +# define TARGET_PAGE_BITS_MIN 12
> +# define TARGET_VIRT_ADDR_SPACE_BITS  63
> +#else
> +# define TARGET_PAGE_BITS 13
> +# define TARGET_VIRT_ADDR_SPACE_BITS  (30 + TARGET_PAGE_BITS)
> +#endif
>   
>   #endif

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>