single-binary: Restrict scope of TARGET_PAGE_BITS_MIN

[PATCH 8/9] page-vary: Move and rename qemu_target_page_bits_min

Posted by Richard Henderson 4 days, 17 hours ago

Rename to migration_legacy_page_bits, to make it clear that
we cannot change the value without causing a migration break.
Move to page-vary.h and page-vary-target.c.
Define via TARGET_PAGE_BITS if not TARGET_PAGE_BITS_VARY.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/page-vary.h   | 9 +++++++++
 include/exec/target_page.h | 1 -
 migration/savevm.c         | 6 +++---
 page-target.c              | 5 -----
 page-vary-target.c         | 9 +++++++++
 5 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/include/exec/page-vary.h b/include/exec/page-vary.h
index 54ddde308a..101c25911c 100644
--- a/include/exec/page-vary.h
+++ b/include/exec/page-vary.h
@@ -49,4 +49,13 @@ bool set_preferred_target_page_bits(int bits);
  */
 void finalize_target_page_bits(void);
 
+/**
+ * migration_legacy_page_bits
+ *
+ * For migration compatibility with qemu v2.9, prior to the introduction
+ * of the configuration/target-page-bits section, return the value of
+ * TARGET_PAGE_BITS that the target had then.
+ */
+int migration_legacy_page_bits(void);
+
 #endif /* EXEC_PAGE_VARY_H */
diff --git a/include/exec/target_page.h b/include/exec/target_page.h
index 8e89e5cbe6..e4bd7f7767 100644
--- a/include/exec/target_page.h
+++ b/include/exec/target_page.h
@@ -63,7 +63,6 @@ static inline int qemu_target_page_bits(void)
     return TARGET_PAGE_BITS;
 }
 
-int qemu_target_page_bits_min(void);
 size_t qemu_target_pages_to_MiB(size_t pages);
 
 #endif
diff --git a/migration/savevm.c b/migration/savevm.c
index c33200a33f..0c12e373b4 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -50,6 +50,7 @@
 #include "system/cpus.h"
 #include "system/memory.h"
 #include "exec/target_page.h"
+#include "exec/page-vary.h"
 #include "trace.h"
 #include "qemu/iov.h"
 #include "qemu/job.h"
@@ -339,7 +340,7 @@ static int configuration_pre_load(void *opaque)
      * predates the variable-target-page-bits support and is using the
      * minimum possible value for this CPU.
      */
-    state->target_page_bits = qemu_target_page_bits_min();
+    state->target_page_bits = migration_legacy_page_bits();
     return 0;
 }
 
@@ -462,8 +463,7 @@ static const VMStateInfo vmstate_info_capability = {
  */
 static bool vmstate_target_page_bits_needed(void *opaque)
 {
-    return qemu_target_page_bits()
-        > qemu_target_page_bits_min();
+    return qemu_target_page_bits() > migration_legacy_page_bits();
 }
 
 static const VMStateDescription vmstate_target_page_bits = {
diff --git a/page-target.c b/page-target.c
index 321e43d06f..8fcd5443b5 100644
--- a/page-target.c
+++ b/page-target.c
@@ -9,11 +9,6 @@
 #include "qemu/osdep.h"
 #include "exec/target_page.h"
 
-int qemu_target_page_bits_min(void)
-{
-    return TARGET_PAGE_BITS_MIN;
-}
-
 /* Convert target pages to MiB (2**20). */
 size_t qemu_target_pages_to_MiB(size_t pages)
 {
diff --git a/page-vary-target.c b/page-vary-target.c
index 84ddeb7c26..6251d948cf 100644
--- a/page-vary-target.c
+++ b/page-vary-target.c
@@ -23,6 +23,15 @@
 #include "exec/page-vary.h"
 #include "exec/target_page.h"
 
+int migration_legacy_page_bits(void)
+{
+#ifdef TARGET_PAGE_BITS_VARY
+    return TARGET_PAGE_BITS_MIN;
+#else
+    return TARGET_PAGE_BITS;
+#endif
+}
+
 bool set_preferred_target_page_bits(int bits)
 {
 #ifdef TARGET_PAGE_BITS_VARY
-- 
2.43.0

Re: [PATCH 8/9] page-vary: Move and rename qemu_target_page_bits_min

Posted by Pierrick Bouvier 4 days, 17 hours ago

On 3/28/25 13:04, Richard Henderson wrote:
> Rename to migration_legacy_page_bits, to make it clear that
> we cannot change the value without causing a migration break.
> Move to page-vary.h and page-vary-target.c.
> Define via TARGET_PAGE_BITS if not TARGET_PAGE_BITS_VARY.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   include/exec/page-vary.h   | 9 +++++++++
>   include/exec/target_page.h | 1 -
>   migration/savevm.c         | 6 +++---
>   page-target.c              | 5 -----
>   page-vary-target.c         | 9 +++++++++
>   5 files changed, 21 insertions(+), 9 deletions(-)
> 
> diff --git a/include/exec/page-vary.h b/include/exec/page-vary.h
> index 54ddde308a..101c25911c 100644
> --- a/include/exec/page-vary.h
> +++ b/include/exec/page-vary.h
> @@ -49,4 +49,13 @@ bool set_preferred_target_page_bits(int bits);
>    */
>   void finalize_target_page_bits(void);
>   
> +/**
> + * migration_legacy_page_bits
> + *
> + * For migration compatibility with qemu v2.9, prior to the introduction
> + * of the configuration/target-page-bits section, return the value of
> + * TARGET_PAGE_BITS that the target had then.
> + */
> +int migration_legacy_page_bits(void);
> +
>   #endif /* EXEC_PAGE_VARY_H */
> diff --git a/include/exec/target_page.h b/include/exec/target_page.h
> index 8e89e5cbe6..e4bd7f7767 100644
> --- a/include/exec/target_page.h
> +++ b/include/exec/target_page.h
> @@ -63,7 +63,6 @@ static inline int qemu_target_page_bits(void)
>       return TARGET_PAGE_BITS;
>   }
>   
> -int qemu_target_page_bits_min(void);
>   size_t qemu_target_pages_to_MiB(size_t pages);
>   
>   #endif
> diff --git a/migration/savevm.c b/migration/savevm.c
> index c33200a33f..0c12e373b4 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -50,6 +50,7 @@
>   #include "system/cpus.h"
>   #include "system/memory.h"
>   #include "exec/target_page.h"
> +#include "exec/page-vary.h"
>   #include "trace.h"
>   #include "qemu/iov.h"
>   #include "qemu/job.h"
> @@ -339,7 +340,7 @@ static int configuration_pre_load(void *opaque)
>        * predates the variable-target-page-bits support and is using the
>        * minimum possible value for this CPU.
>        */
> -    state->target_page_bits = qemu_target_page_bits_min();
> +    state->target_page_bits = migration_legacy_page_bits();
>       return 0;
>   }
>   
> @@ -462,8 +463,7 @@ static const VMStateInfo vmstate_info_capability = {
>    */
>   static bool vmstate_target_page_bits_needed(void *opaque)
>   {
> -    return qemu_target_page_bits()
> -        > qemu_target_page_bits_min();
> +    return qemu_target_page_bits() > migration_legacy_page_bits();
>   }
>   
>   static const VMStateDescription vmstate_target_page_bits = {
> diff --git a/page-target.c b/page-target.c
> index 321e43d06f..8fcd5443b5 100644
> --- a/page-target.c
> +++ b/page-target.c
> @@ -9,11 +9,6 @@
>   #include "qemu/osdep.h"
>   #include "exec/target_page.h"
>   
> -int qemu_target_page_bits_min(void)
> -{
> -    return TARGET_PAGE_BITS_MIN;
> -}
> -
>   /* Convert target pages to MiB (2**20). */
>   size_t qemu_target_pages_to_MiB(size_t pages)
>   {
> diff --git a/page-vary-target.c b/page-vary-target.c
> index 84ddeb7c26..6251d948cf 100644
> --- a/page-vary-target.c
> +++ b/page-vary-target.c
> @@ -23,6 +23,15 @@
>   #include "exec/page-vary.h"
>   #include "exec/target_page.h"
>   
> +int migration_legacy_page_bits(void)
> +{
> +#ifdef TARGET_PAGE_BITS_VARY
> +    return TARGET_PAGE_BITS_MIN;
> +#else
> +    return TARGET_PAGE_BITS;
> +#endif
> +}
> +
>   bool set_preferred_target_page_bits(int bits)
>   {
>   #ifdef TARGET_PAGE_BITS_VARY

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