The only place we really need to know the minimum is within
page-vary-target.c. Rename the target/arm TARGET_PAGE_BITS_MIN
to TARGE_PAGE_BITS_LEGACY to emphasize what it really means.
Move the assertions related to minimum page size as well.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
include/exec/cpu-defs.h | 10 ++--------
include/exec/poison.h | 1 +
include/exec/target_page.h | 1 -
include/qemu/osdep.h | 6 ++++++
target/alpha/cpu-param.h | 1 -
target/arm/cpu-param.h | 3 +--
target/ppc/cpu-param.h | 1 -
accel/tcg/cputlb.c | 1 -
page-vary-target.c | 39 +++++++++++++++++++++++++++++++++++---
9 files changed, 46 insertions(+), 17 deletions(-)
diff --git a/include/exec/cpu-defs.h b/include/exec/cpu-defs.h
index 9f955f53fd..e01acb7c90 100644
--- a/include/exec/cpu-defs.h
+++ b/include/exec/cpu-defs.h
@@ -34,14 +34,8 @@
#ifndef TARGET_VIRT_ADDR_SPACE_BITS
# error TARGET_VIRT_ADDR_SPACE_BITS must be defined in cpu-param.h
#endif
-#ifndef TARGET_PAGE_BITS
-# ifdef TARGET_PAGE_BITS_VARY
-# ifndef TARGET_PAGE_BITS_MIN
-# error TARGET_PAGE_BITS_MIN must be defined in cpu-param.h
-# endif
-# else
-# error TARGET_PAGE_BITS must be defined in cpu-param.h
-# endif
+#if !defined(TARGET_PAGE_BITS) && !defined(TARGET_PAGE_BITS_VARY)
+# error TARGET_PAGE_BITS must be defined in cpu-param.h
#endif
#include "exec/target_long.h"
diff --git a/include/exec/poison.h b/include/exec/poison.h
index 4180a5a489..c4f7ee22bf 100644
--- a/include/exec/poison.h
+++ b/include/exec/poison.h
@@ -44,6 +44,7 @@
#pragma GCC poison TARGET_FMT_lu
#pragma GCC poison TARGET_PHYS_ADDR_SPACE_BITS
+#pragma GCC poison TARGET_PAGE_BITS_LEGACY
#pragma GCC poison CONFIG_ALPHA_DIS
#pragma GCC poison CONFIG_HPPA_DIS
diff --git a/include/exec/target_page.h b/include/exec/target_page.h
index e4bd7f7767..ca0ebbc8bb 100644
--- a/include/exec/target_page.h
+++ b/include/exec/target_page.h
@@ -41,7 +41,6 @@ extern const TargetPageBits target_page;
# endif
# define TARGET_PAGE_SIZE (-(int)TARGET_PAGE_MASK)
#else
-# define TARGET_PAGE_BITS_MIN TARGET_PAGE_BITS
# define TARGET_PAGE_SIZE (1 << TARGET_PAGE_BITS)
# define TARGET_PAGE_MASK ((TARGET_PAGE_TYPE)-1 << TARGET_PAGE_BITS)
#endif
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 4397a90680..321a52d7f0 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -50,6 +50,12 @@
*/
#pragma GCC poison TARGET_WORDS_BIGENDIAN
+/*
+ * TARGET_PAGE_BITS_MIN was repaced by TARGET_PAGE_BITS_LEGACY
+ * for system mode. Prevent it from creeping back in.
+ */
+#pragma GCC poison TARGET_PAGE_BITS_MIN
+
#include "qemu/compiler.h"
/* Older versions of C++ don't get definitions of various macros from
diff --git a/target/alpha/cpu-param.h b/target/alpha/cpu-param.h
index ff06e41497..63989e71c0 100644
--- a/target/alpha/cpu-param.h
+++ b/target/alpha/cpu-param.h
@@ -18,7 +18,6 @@
* 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
diff --git a/target/arm/cpu-param.h b/target/arm/cpu-param.h
index 896b35bd6d..a7ae42d17d 100644
--- a/target/arm/cpu-param.h
+++ b/target/arm/cpu-param.h
@@ -24,7 +24,6 @@
# else
/* Allow user-only to vary page size from 4k */
# define TARGET_PAGE_BITS_VARY
-# define TARGET_PAGE_BITS_MIN 12
# endif
# else
# define TARGET_PAGE_BITS 12
@@ -35,7 +34,7 @@
* have to support 1K tiny pages.
*/
# define TARGET_PAGE_BITS_VARY
-# define TARGET_PAGE_BITS_MIN 10
+# define TARGET_PAGE_BITS_LEGACY 10
#endif /* !CONFIG_USER_ONLY */
/* ARM processors have a weak memory model */
diff --git a/target/ppc/cpu-param.h b/target/ppc/cpu-param.h
index 6c4525fdf3..553ad2f4c6 100644
--- a/target/ppc/cpu-param.h
+++ b/target/ppc/cpu-param.h
@@ -33,7 +33,6 @@
#ifdef CONFIG_USER_ONLY
/* Allow user-only to vary page size from 4k */
# define TARGET_PAGE_BITS_VARY
-# define TARGET_PAGE_BITS_MIN 12
#else
# define TARGET_PAGE_BITS 12
#endif
diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index 39314e86f3..0de46903dd 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -49,7 +49,6 @@
#endif
#include "tcg/tcg-ldst.h"
-QEMU_BUILD_BUG_ON(TLB_FLAGS_MASK & ((1u < TARGET_PAGE_BITS_MIN) - 1));
/* DEBUG defines, enable DEBUG_TLB_LOG to log to the CPU_LOG_MMU target */
/* #define DEBUG_TLB */
diff --git a/page-vary-target.c b/page-vary-target.c
index 6251d948cf..d83f9a6a90 100644
--- a/page-vary-target.c
+++ b/page-vary-target.c
@@ -23,19 +23,45 @@
#include "exec/page-vary.h"
#include "exec/target_page.h"
+
+/*
+ * For system mode, the minimum comes from the number of bits
+ * required for maximum alignment (6) and the number of bits
+ * required for TLB_FLAGS_MASK (3).
+ *
+ * For user mode, TARGET_PAGE_BITS_VARY is a hack to allow the target
+ * page size to match the host page size. Mostly, this reduces the
+ * ordinary target page size to run on a host with 4KiB pages (i.e. x86).
+ * There is no true minimum required by the implementation, but keep the
+ * same minimum as for system mode for sanity.
+ * See linux-user/mmap.c, mmap_h_lt_g and mmap_h_gt_g.
+ */
+#define TARGET_PAGE_BITS__MIN 9
+
+#ifndef TARGET_PAGE_BITS_VARY
+QEMU_BUILD_BUG_ON(TARGET_PAGE_BITS < TARGET_PAGE_BITS__MIN);
+#endif
+
+#ifndef CONFIG_USER_ONLY
+#include "exec/tlb-flags.h"
+
+QEMU_BUILD_BUG_ON(TLB_FLAGS_MASK & ((1u < TARGET_PAGE_BITS__MIN) - 1));
+
int migration_legacy_page_bits(void)
{
#ifdef TARGET_PAGE_BITS_VARY
- return TARGET_PAGE_BITS_MIN;
+ QEMU_BUILD_BUG_ON(TARGET_PAGE_BITS_LEGACY < TARGET_PAGE_BITS__MIN);
+ return TARGET_PAGE_BITS_LEGACY;
#else
return TARGET_PAGE_BITS;
#endif
}
+#endif
bool set_preferred_target_page_bits(int bits)
{
+ assert(bits >= TARGET_PAGE_BITS__MIN);
#ifdef TARGET_PAGE_BITS_VARY
- assert(bits >= TARGET_PAGE_BITS_MIN);
return set_preferred_target_page_bits_common(bits);
#else
return true;
@@ -44,5 +70,12 @@ bool set_preferred_target_page_bits(int bits)
void finalize_target_page_bits(void)
{
- finalize_target_page_bits_common(TARGET_PAGE_BITS_MIN);
+#ifndef TARGET_PAGE_BITS_VARY
+ finalize_target_page_bits_common(TARGET_PAGE_BITS);
+#elif defined(CONFIG_USER_ONLY)
+ assert(target_page.bits != 0);
+ finalize_target_page_bits_common(target_page.bits);
+#else
+ finalize_target_page_bits_common(TARGET_PAGE_BITS_LEGACY);
+#endif
}
--
2.43.0On 3/28/25 13:04, Richard Henderson wrote:
> The only place we really need to know the minimum is within
> page-vary-target.c. Rename the target/arm TARGET_PAGE_BITS_MIN
> to TARGE_PAGE_BITS_LEGACY to emphasize what it really means.
> Move the assertions related to minimum page size as well.
>
s/TARGE_PAGE_BITS_LEGACY/TARGET_PAGE_BITS_LEGACY
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> include/exec/cpu-defs.h | 10 ++--------
> include/exec/poison.h | 1 +
> include/exec/target_page.h | 1 -
> include/qemu/osdep.h | 6 ++++++
> target/alpha/cpu-param.h | 1 -
> target/arm/cpu-param.h | 3 +--
> target/ppc/cpu-param.h | 1 -
> accel/tcg/cputlb.c | 1 -
> page-vary-target.c | 39 +++++++++++++++++++++++++++++++++++---
> 9 files changed, 46 insertions(+), 17 deletions(-)
>
> diff --git a/include/exec/cpu-defs.h b/include/exec/cpu-defs.h
> index 9f955f53fd..e01acb7c90 100644
> --- a/include/exec/cpu-defs.h
> +++ b/include/exec/cpu-defs.h
> @@ -34,14 +34,8 @@
> #ifndef TARGET_VIRT_ADDR_SPACE_BITS
> # error TARGET_VIRT_ADDR_SPACE_BITS must be defined in cpu-param.h
> #endif
> -#ifndef TARGET_PAGE_BITS
> -# ifdef TARGET_PAGE_BITS_VARY
> -# ifndef TARGET_PAGE_BITS_MIN
> -# error TARGET_PAGE_BITS_MIN must be defined in cpu-param.h
> -# endif
> -# else
> -# error TARGET_PAGE_BITS must be defined in cpu-param.h
> -# endif
> +#if !defined(TARGET_PAGE_BITS) && !defined(TARGET_PAGE_BITS_VARY)
> +# error TARGET_PAGE_BITS must be defined in cpu-param.h
> #endif
>
> #include "exec/target_long.h"
> diff --git a/include/exec/poison.h b/include/exec/poison.h
> index 4180a5a489..c4f7ee22bf 100644
> --- a/include/exec/poison.h
> +++ b/include/exec/poison.h
> @@ -44,6 +44,7 @@
> #pragma GCC poison TARGET_FMT_lu
>
> #pragma GCC poison TARGET_PHYS_ADDR_SPACE_BITS
> +#pragma GCC poison TARGET_PAGE_BITS_LEGACY
>
> #pragma GCC poison CONFIG_ALPHA_DIS
> #pragma GCC poison CONFIG_HPPA_DIS
> diff --git a/include/exec/target_page.h b/include/exec/target_page.h
> index e4bd7f7767..ca0ebbc8bb 100644
> --- a/include/exec/target_page.h
> +++ b/include/exec/target_page.h
> @@ -41,7 +41,6 @@ extern const TargetPageBits target_page;
> # endif
> # define TARGET_PAGE_SIZE (-(int)TARGET_PAGE_MASK)
> #else
> -# define TARGET_PAGE_BITS_MIN TARGET_PAGE_BITS
> # define TARGET_PAGE_SIZE (1 << TARGET_PAGE_BITS)
> # define TARGET_PAGE_MASK ((TARGET_PAGE_TYPE)-1 << TARGET_PAGE_BITS)
> #endif
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 4397a90680..321a52d7f0 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -50,6 +50,12 @@
> */
> #pragma GCC poison TARGET_WORDS_BIGENDIAN
>
> +/*
> + * TARGET_PAGE_BITS_MIN was repaced by TARGET_PAGE_BITS_LEGACY
> + * for system mode. Prevent it from creeping back in.
> + */
s/repaced/replaced
> +#pragma GCC poison TARGET_PAGE_BITS_MIN
> +
> #include "qemu/compiler.h"
>
> /* Older versions of C++ don't get definitions of various macros from
> diff --git a/target/alpha/cpu-param.h b/target/alpha/cpu-param.h
> index ff06e41497..63989e71c0 100644
> --- a/target/alpha/cpu-param.h
> +++ b/target/alpha/cpu-param.h
> @@ -18,7 +18,6 @@
> * 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
> diff --git a/target/arm/cpu-param.h b/target/arm/cpu-param.h
> index 896b35bd6d..a7ae42d17d 100644
> --- a/target/arm/cpu-param.h
> +++ b/target/arm/cpu-param.h
> @@ -24,7 +24,6 @@
> # else
> /* Allow user-only to vary page size from 4k */
> # define TARGET_PAGE_BITS_VARY
> -# define TARGET_PAGE_BITS_MIN 12
> # endif
> # else
> # define TARGET_PAGE_BITS 12
> @@ -35,7 +34,7 @@
> * have to support 1K tiny pages.
> */
> # define TARGET_PAGE_BITS_VARY
> -# define TARGET_PAGE_BITS_MIN 10
> +# define TARGET_PAGE_BITS_LEGACY 10
> #endif /* !CONFIG_USER_ONLY */
>
> /* ARM processors have a weak memory model */
> diff --git a/target/ppc/cpu-param.h b/target/ppc/cpu-param.h
> index 6c4525fdf3..553ad2f4c6 100644
> --- a/target/ppc/cpu-param.h
> +++ b/target/ppc/cpu-param.h
> @@ -33,7 +33,6 @@
> #ifdef CONFIG_USER_ONLY
> /* Allow user-only to vary page size from 4k */
> # define TARGET_PAGE_BITS_VARY
> -# define TARGET_PAGE_BITS_MIN 12
> #else
> # define TARGET_PAGE_BITS 12
> #endif
> diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
> index 39314e86f3..0de46903dd 100644
> --- a/accel/tcg/cputlb.c
> +++ b/accel/tcg/cputlb.c
> @@ -49,7 +49,6 @@
> #endif
> #include "tcg/tcg-ldst.h"
>
> -QEMU_BUILD_BUG_ON(TLB_FLAGS_MASK & ((1u < TARGET_PAGE_BITS_MIN) - 1));
>
> /* DEBUG defines, enable DEBUG_TLB_LOG to log to the CPU_LOG_MMU target */
> /* #define DEBUG_TLB */
> diff --git a/page-vary-target.c b/page-vary-target.c
> index 6251d948cf..d83f9a6a90 100644
> --- a/page-vary-target.c
> +++ b/page-vary-target.c
> @@ -23,19 +23,45 @@
> #include "exec/page-vary.h"
> #include "exec/target_page.h"
>
> +
> +/*
> + * For system mode, the minimum comes from the number of bits
> + * required for maximum alignment (6) and the number of bits
> + * required for TLB_FLAGS_MASK (3).
> + *
> + * For user mode, TARGET_PAGE_BITS_VARY is a hack to allow the target
> + * page size to match the host page size. Mostly, this reduces the
> + * ordinary target page size to run on a host with 4KiB pages (i.e. x86).
> + * There is no true minimum required by the implementation, but keep the
> + * same minimum as for system mode for sanity.
> + * See linux-user/mmap.c, mmap_h_lt_g and mmap_h_gt_g.
> + */
> +#define TARGET_PAGE_BITS__MIN 9
> +
> +#ifndef TARGET_PAGE_BITS_VARY
> +QEMU_BUILD_BUG_ON(TARGET_PAGE_BITS < TARGET_PAGE_BITS__MIN);
> +#endif
> +
> +#ifndef CONFIG_USER_ONLY
> +#include "exec/tlb-flags.h"
> +
> +QEMU_BUILD_BUG_ON(TLB_FLAGS_MASK & ((1u < TARGET_PAGE_BITS__MIN) - 1));
> +
> int migration_legacy_page_bits(void)
> {
> #ifdef TARGET_PAGE_BITS_VARY
> - return TARGET_PAGE_BITS_MIN;
> + QEMU_BUILD_BUG_ON(TARGET_PAGE_BITS_LEGACY < TARGET_PAGE_BITS__MIN);
> + return TARGET_PAGE_BITS_LEGACY;
> #else
> return TARGET_PAGE_BITS;
> #endif
> }
> +#endif
>
> bool set_preferred_target_page_bits(int bits)
> {
> + assert(bits >= TARGET_PAGE_BITS__MIN);
> #ifdef TARGET_PAGE_BITS_VARY
> - assert(bits >= TARGET_PAGE_BITS_MIN);
> return set_preferred_target_page_bits_common(bits);
> #else
> return true;
> @@ -44,5 +70,12 @@ bool set_preferred_target_page_bits(int bits)
>
> void finalize_target_page_bits(void)
> {
> - finalize_target_page_bits_common(TARGET_PAGE_BITS_MIN);
> +#ifndef TARGET_PAGE_BITS_VARY
> + finalize_target_page_bits_common(TARGET_PAGE_BITS);
> +#elif defined(CONFIG_USER_ONLY)
> + assert(target_page.bits != 0);
> + finalize_target_page_bits_common(target_page.bits);
> +#else
> + finalize_target_page_bits_common(TARGET_PAGE_BITS_LEGACY);
> +#endif
> }
Great!
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Any chance we would rename TARGET_PAGE_BITS__MIN? (MIN_ALL? ALL_MIN?
ARCH_MIN? any other idea)
I know it's restricted to this file only, but the __ is surprising.
On 3/28/25 15:38, Pierrick Bouvier wrote: > Any chance we would rename TARGET_PAGE_BITS__MIN? (MIN_ALL? ALL_MIN? ARCH_MIN? any other > idea) > I know it's restricted to this file only, but the __ is surprising. I could drop the poisoning. Since there have only ever been two targets using TARGET_PAGE_BITS_VARY, it's unlikely creep back in unawares. r~
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