[PATCH 0/7] exec: Improve code for TARGET_PAGE_BITS_VARY

[PATCH 0/7] exec: Improve code for TARGET_PAGE_BITS_VARY

[Richard Henderson]

There's currently a fair amount of overhead in the way we currently
treat TARGET_PAGE_{BITS,SIZE,MASK} with TARGET_PAGE_BITS_VARY.

We have assertions that TARGET_PAGE_BITS has been finalized.  Which
is fine, but the variable that controls the assertion may be assumed
to be modified by any function call, which means that we have lots
of duplicate assertions.

This re-arranges things using a const symbol, which allows the compiler
to assume that the variable is not modified across calls.  In order to
allow initialization of the variable during startup, use an alias that
is non-const and controls the allocation into a read-write section.

Remove the assertion for release builds.

Precompute TARGET_PAGE_MASK.  This removes a runtime shift and allows
the variable to be used as a direct memory operand on x86.

Size reductions vs master for qemu-system-aarch64 for various hosts:

PPC64LE:
  debug-tcg:  -32264
  release:    -44360
AARCH64:
  debug-tcg:  -33304
  relase:     -77080
X86_64:
  debug-tcg:   -6685
  relase:     -15597


r~


Richard Henderson (7):
  exec: Use TARGET_PAGE_BITS_MIN for TLB flags
  exec: Split out variable page size support to exec-vary.c
  exec: Use const alias for TARGET_PAGE_BITS_VARY
  exec: Restrict TARGET_PAGE_BITS_VARY assert to CONFIG_DEBUG_TCG
  exec: Promote TARGET_PAGE_MASK to target_long
  exec: Tidy TARGET_PAGE_ALIGN
  exec: Cache TARGET_PAGE_MASK for TARGET_PAGE_BITS_VARY

 Makefile.target        |  2 +-
 include/exec/cpu-all.h | 41 +++++++++++++-------
 include/qemu-common.h  |  6 +++
 exec-vary.c            | 88 ++++++++++++++++++++++++++++++++++++++++++
 exec.c                 | 34 ----------------
 5 files changed, 123 insertions(+), 48 deletions(-)
 create mode 100644 exec-vary.c

-- 
2.17.1

[PATCH 1/7] exec: Use TARGET_PAGE_BITS_MIN for TLB flags

[Richard Henderson]

These bits do not need to vary with the actual page size
used by the guest.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/cpu-all.h | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index d2d443c4f9..e0c8dc540c 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -317,20 +317,24 @@ CPUArchState *cpu_copy(CPUArchState *env);
 
 #if !defined(CONFIG_USER_ONLY)
 
-/* Flags stored in the low bits of the TLB virtual address.  These are
- * defined so that fast path ram access is all zeros.
+/*
+ * Flags stored in the low bits of the TLB virtual address.
+ * These are defined so that fast path ram access is all zeros.
  * The flags all must be between TARGET_PAGE_BITS and
  * maximum address alignment bit.
+ *
+ * Use TARGET_PAGE_BITS_MIN so that these bits are constant
+ * when TARGET_PAGE_BITS_VARY is in effect.
  */
 /* Zero if TLB entry is valid.  */
-#define TLB_INVALID_MASK    (1 << (TARGET_PAGE_BITS - 1))
+#define TLB_INVALID_MASK    (1 << (TARGET_PAGE_BITS_MIN - 1))
 /* Set if TLB entry references a clean RAM page.  The iotlb entry will
    contain the page physical address.  */
-#define TLB_NOTDIRTY        (1 << (TARGET_PAGE_BITS - 2))
+#define TLB_NOTDIRTY        (1 << (TARGET_PAGE_BITS_MIN - 2))
 /* Set if TLB entry is an IO callback.  */
-#define TLB_MMIO            (1 << (TARGET_PAGE_BITS - 3))
+#define TLB_MMIO            (1 << (TARGET_PAGE_BITS_MIN - 3))
 /* Set if TLB entry contains a watchpoint.  */
-#define TLB_WATCHPOINT      (1 << (TARGET_PAGE_BITS - 4))
+#define TLB_WATCHPOINT      (1 << (TARGET_PAGE_BITS_MIN - 4))
 
 /* Use this mask to check interception with an alignment mask
  * in a TCG backend.
-- 
2.17.1

[PATCH 2/7] exec: Split out variable page size support to exec-vary.c

[Richard Henderson]

The next patch will play a trick with "const" that will
confuse the compiler about the uses of target_page_bits
within exec.c.  Moving everything to a new file prevents
this confusion.

No functional change so far.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 Makefile.target       |  2 +-
 include/qemu-common.h |  6 +++++
 exec-vary.c           | 57 +++++++++++++++++++++++++++++++++++++++++++
 exec.c                | 34 --------------------------
 4 files changed, 64 insertions(+), 35 deletions(-)
 create mode 100644 exec-vary.c

diff --git a/Makefile.target b/Makefile.target
index 5e916230c4..ca3d14efe1 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -107,7 +107,7 @@ obj-y += trace/
 
 #########################################################
 # cpu emulator library
-obj-y += exec.o
+obj-y += exec.o exec-vary.o
 obj-y += accel/
 obj-$(CONFIG_TCG) += tcg/tcg.o tcg/tcg-op.o tcg/tcg-op-vec.o tcg/tcg-op-gvec.o
 obj-$(CONFIG_TCG) += tcg/tcg-common.o tcg/optimize.o
diff --git a/include/qemu-common.h b/include/qemu-common.h
index 0235cd3b91..3e800c2224 100644
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -74,6 +74,12 @@ void cpu_exec_step_atomic(CPUState *cpu);
  */
 bool set_preferred_target_page_bits(int bits);
 
+/**
+ * finalize_target_page_bits:
+ * Commit the final value set by set_preferred_target_page_bits.
+ */
+void finalize_target_page_bits(void);
+
 /**
  * Sends a (part of) iovec down a socket, yielding when the socket is full, or
  * Receives data into a (part of) iovec from a socket,
diff --git a/exec-vary.c b/exec-vary.c
new file mode 100644
index 0000000000..48c0ab306c
--- /dev/null
+++ b/exec-vary.c
@@ -0,0 +1,57 @@
+/*
+ * Variable page size handling
+ *
+ *  Copyright (c) 2003 Fabrice Bellard
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "exec/exec-all.h"
+
+#ifdef TARGET_PAGE_BITS_VARY
+int target_page_bits;
+bool target_page_bits_decided;
+#endif
+
+bool set_preferred_target_page_bits(int bits)
+{
+    /*
+     * The target page size is the lowest common denominator for all
+     * the CPUs in the system, so we can only make it smaller, never
+     * larger. And we can't make it smaller once we've committed to
+     * a particular size.
+     */
+#ifdef TARGET_PAGE_BITS_VARY
+    assert(bits >= TARGET_PAGE_BITS_MIN);
+    if (target_page_bits == 0 || target_page_bits > bits) {
+        if (target_page_bits_decided) {
+            return false;
+        }
+        target_page_bits = bits;
+    }
+#endif
+    return true;
+}
+
+void finalize_target_page_bits(void)
+{
+#ifdef TARGET_PAGE_BITS_VARY
+    if (target_page_bits == 0) {
+        target_page_bits = TARGET_PAGE_BITS_MIN;
+    }
+    target_page_bits_decided = true;
+#endif
+}
diff --git a/exec.c b/exec.c
index 8b998974f8..33bd0e36c1 100644
--- a/exec.c
+++ b/exec.c
@@ -92,11 +92,6 @@ MemoryRegion io_mem_rom, io_mem_notdirty;
 static MemoryRegion io_mem_unassigned;
 #endif
 
-#ifdef TARGET_PAGE_BITS_VARY
-int target_page_bits;
-bool target_page_bits_decided;
-#endif
-
 CPUTailQ cpus = QTAILQ_HEAD_INITIALIZER(cpus);
 
 /* current CPU in the current thread. It is only valid inside
@@ -110,37 +105,8 @@ int use_icount;
 uintptr_t qemu_host_page_size;
 intptr_t qemu_host_page_mask;
 
-bool set_preferred_target_page_bits(int bits)
-{
-    /* The target page size is the lowest common denominator for all
-     * the CPUs in the system, so we can only make it smaller, never
-     * larger. And we can't make it smaller once we've committed to
-     * a particular size.
-     */
-#ifdef TARGET_PAGE_BITS_VARY
-    assert(bits >= TARGET_PAGE_BITS_MIN);
-    if (target_page_bits == 0 || target_page_bits > bits) {
-        if (target_page_bits_decided) {
-            return false;
-        }
-        target_page_bits = bits;
-    }
-#endif
-    return true;
-}
-
 #if !defined(CONFIG_USER_ONLY)
 
-static void finalize_target_page_bits(void)
-{
-#ifdef TARGET_PAGE_BITS_VARY
-    if (target_page_bits == 0) {
-        target_page_bits = TARGET_PAGE_BITS_MIN;
-    }
-    target_page_bits_decided = true;
-#endif
-}
-
 typedef struct PhysPageEntry PhysPageEntry;
 
 struct PhysPageEntry {
-- 
2.17.1

[PATCH 3/7] exec: Use const alias for TARGET_PAGE_BITS_VARY

[Richard Henderson]

Using a variable that is declared "const" for this tells the
compiler that it may read the value once and assume that it
does not change across function calls.

For target_page_size, this means we have only one assert per
function, and one read of the variable.

This reduces the size of qemu-system-aarch64 by 8k.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/cpu-all.h | 10 +++++----
 exec-vary.c            | 46 ++++++++++++++++++++++++++++++++++--------
 2 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index e0c8dc540c..a53b761b48 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -210,10 +210,12 @@ static inline void stl_phys_notdirty(AddressSpace *as, hwaddr addr, uint32_t val
 /* page related stuff */
 
 #ifdef TARGET_PAGE_BITS_VARY
-extern bool target_page_bits_decided;
-extern int target_page_bits;
-#define TARGET_PAGE_BITS ({ assert(target_page_bits_decided); \
-                            target_page_bits; })
+typedef struct {
+    bool decided;
+    int bits;
+} TargetPageBits;
+extern const TargetPageBits target_page;
+#define TARGET_PAGE_BITS (assert(target_page.decided), target_page.bits)
 #else
 #define TARGET_PAGE_BITS_MIN TARGET_PAGE_BITS
 #endif
diff --git a/exec-vary.c b/exec-vary.c
index 48c0ab306c..67cdf57a9c 100644
--- a/exec-vary.c
+++ b/exec-vary.c
@@ -22,8 +22,38 @@
 #include "exec/exec-all.h"
 
 #ifdef TARGET_PAGE_BITS_VARY
-int target_page_bits;
-bool target_page_bits_decided;
+/*
+ * We want to declare the "target_page" variable as const, which tells
+ * the compiler that it can cache any value that it reads across calls.
+ * This avoids multiple assertions and multiple reads within any one user.
+ *
+ * This works because we initialize the target_page data very early, in a
+ * location far removed from the functions that require the final results.
+ *
+ * This also requires that we have a non-constant symbol by which we can
+ * perform the actual initialization, and which forces the data to be
+ * allocated within writable memory.  Thus "init_target_page", and we use
+ * that symbol exclusively in the two functions that initialize this value.
+ *
+ * The "target_page" symbol is created as an alias of "init_target_page".
+ */
+static TargetPageBits init_target_page;
+
+/*
+ * Note that this is *not* a redundant decl, this is the definition of
+ * the "target_page" symbol.  The syntax for this definition requires
+ * the use of the extern keyword.  This seems to be a GCC bug in
+ * either the syntax for the alias attribute or in -Wredundant-decls.
+ *
+ * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91765
+ */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wredundant-decls"
+
+extern const TargetPageBits target_page
+    __attribute__((alias("init_target_page")));
+
+#pragma GCC diagnostic pop
 #endif
 
 bool set_preferred_target_page_bits(int bits)
@@ -36,11 +66,11 @@ bool set_preferred_target_page_bits(int bits)
      */
 #ifdef TARGET_PAGE_BITS_VARY
     assert(bits >= TARGET_PAGE_BITS_MIN);
-    if (target_page_bits == 0 || target_page_bits > bits) {
-        if (target_page_bits_decided) {
+    if (init_target_page.bits == 0 || init_target_page.bits > bits) {
+        if (init_target_page.decided) {
             return false;
         }
-        target_page_bits = bits;
+        init_target_page.bits = bits;
     }
 #endif
     return true;
@@ -49,9 +79,9 @@ bool set_preferred_target_page_bits(int bits)
 void finalize_target_page_bits(void)
 {
 #ifdef TARGET_PAGE_BITS_VARY
-    if (target_page_bits == 0) {
-        target_page_bits = TARGET_PAGE_BITS_MIN;
+    if (init_target_page.bits == 0) {
+        init_target_page.bits = TARGET_PAGE_BITS_MIN;
     }
-    target_page_bits_decided = true;
+    init_target_page.decided = true;
 #endif
 }
-- 
2.17.1

[PATCH 4/7] exec: Restrict TARGET_PAGE_BITS_VARY assert to CONFIG_DEBUG_TCG

[Richard Henderson]

This reduces the size of a release build by about 10k.
Noticably, within the tlb miss helpers.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/cpu-all.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index a53b761b48..b11ee1f711 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -215,7 +215,11 @@ typedef struct {
     int bits;
 } TargetPageBits;
 extern const TargetPageBits target_page;
-#define TARGET_PAGE_BITS (assert(target_page.decided), target_page.bits)
+# ifdef CONFIG_DEBUG_TCG
+#  define TARGET_PAGE_BITS (assert(target_page.decided), target_page.bits)
+# else
+#  define TARGET_PAGE_BITS target_page.bits
+# endif
 #else
 #define TARGET_PAGE_BITS_MIN TARGET_PAGE_BITS
 #endif
-- 
2.17.1

[PATCH 5/7] exec: Promote TARGET_PAGE_MASK to target_long

[Richard Henderson]

There are some uint64_t uses that expect TARGET_PAGE_MASK to
extend for a 32-bit, so this must continue to be a signed type.
Define based on TARGET_PAGE_BITS not TARGET_PAGE_SIZE; this
will make a following patch more clear.

This should not have a functional effect so far.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/cpu-all.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index b11ee1f711..34d36cebca 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -225,7 +225,7 @@ extern const TargetPageBits target_page;
 #endif
 
 #define TARGET_PAGE_SIZE (1 << TARGET_PAGE_BITS)
-#define TARGET_PAGE_MASK ~(TARGET_PAGE_SIZE - 1)
+#define TARGET_PAGE_MASK ((target_long)-1 << TARGET_PAGE_BITS)
 #define TARGET_PAGE_ALIGN(addr) (((addr) + TARGET_PAGE_SIZE - 1) & TARGET_PAGE_MASK)
 
 /* Using intptr_t ensures that qemu_*_page_mask is sign-extended even
-- 
2.17.1

[PATCH 6/7] exec: Tidy TARGET_PAGE_ALIGN

[Richard Henderson]

Use TARGET_PAGE_MASK twice instead of TARGET_PAGE_SIZE once.
This is functionally identical, but will help a following patch.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/cpu-all.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 34d36cebca..5246770271 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -226,7 +226,8 @@ extern const TargetPageBits target_page;
 
 #define TARGET_PAGE_SIZE (1 << TARGET_PAGE_BITS)
 #define TARGET_PAGE_MASK ((target_long)-1 << TARGET_PAGE_BITS)
-#define TARGET_PAGE_ALIGN(addr) (((addr) + TARGET_PAGE_SIZE - 1) & TARGET_PAGE_MASK)
+#define TARGET_PAGE_ALIGN(addr) \
+    (((addr) + ~TARGET_PAGE_MASK) & TARGET_PAGE_MASK)
 
 /* Using intptr_t ensures that qemu_*_page_mask is sign-extended even
  * when intptr_t is 32-bit and we are aligning a long long.
-- 
2.17.1

[PATCH 7/7] exec: Cache TARGET_PAGE_MASK for TARGET_PAGE_BITS_VARY

[Richard Henderson]

This eliminates a set of runtime shifts.  It turns out that we
require TARGET_PAGE_MASK more often than TARGET_PAGE_SIZE, so
redefine TARGET_PAGE_SIZE based on TARGET_PAGE_MASK instead of
the other way around.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/cpu-all.h | 8 ++++++--
 exec-vary.c            | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 5246770271..2db73c7a27 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -213,19 +213,23 @@ static inline void stl_phys_notdirty(AddressSpace *as, hwaddr addr, uint32_t val
 typedef struct {
     bool decided;
     int bits;
+    target_long mask;
 } TargetPageBits;
 extern const TargetPageBits target_page;
 # ifdef CONFIG_DEBUG_TCG
 #  define TARGET_PAGE_BITS (assert(target_page.decided), target_page.bits)
+#  define TARGET_PAGE_MASK (assert(target_page.decided), target_page.mask)
 # else
 #  define TARGET_PAGE_BITS target_page.bits
+#  define TARGET_PAGE_MASK target_page.mask
 # 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_long)-1 << TARGET_PAGE_BITS)
 #endif
 
-#define TARGET_PAGE_SIZE (1 << TARGET_PAGE_BITS)
-#define TARGET_PAGE_MASK ((target_long)-1 << TARGET_PAGE_BITS)
 #define TARGET_PAGE_ALIGN(addr) \
     (((addr) + ~TARGET_PAGE_MASK) & TARGET_PAGE_MASK)
 
diff --git a/exec-vary.c b/exec-vary.c
index 67cdf57a9c..26daf281f2 100644
--- a/exec-vary.c
+++ b/exec-vary.c
@@ -83,5 +83,6 @@ void finalize_target_page_bits(void)
         init_target_page.bits = TARGET_PAGE_BITS_MIN;
     }
     init_target_page.decided = true;
+    init_target_page.mask = (target_long)-1 << init_target_page.bits;
 #endif
 }
-- 
2.17.1

Re: [PATCH 0/7] exec: Improve code for TARGET_PAGE_BITS_VARY

[Paolo Bonzini]

On 20/09/19 01:29, Richard Henderson wrote:
> There's currently a fair amount of overhead in the way we currently
> treat TARGET_PAGE_{BITS,SIZE,MASK} with TARGET_PAGE_BITS_VARY.
> 
> We have assertions that TARGET_PAGE_BITS has been finalized.  Which
> is fine, but the variable that controls the assertion may be assumed
> to be modified by any function call, which means that we have lots
> of duplicate assertions.
> 
> This re-arranges things using a const symbol, which allows the compiler
> to assume that the variable is not modified across calls.  In order to
> allow initialization of the variable during startup, use an alias that
> is non-const and controls the allocation into a read-write section.
> 
> Remove the assertion for release builds.
> 
> Precompute TARGET_PAGE_MASK.  This removes a runtime shift and allows
> the variable to be used as a direct memory operand on x86.
> 
> Size reductions vs master for qemu-system-aarch64 for various hosts:
> 
> PPC64LE:
>   debug-tcg:  -32264
>   release:    -44360
> AARCH64:
>   debug-tcg:  -33304
>   relase:     -77080
> X86_64:
>   debug-tcg:   -6685
>   relase:     -15597
> 
> 
> r~
> 
> 
> Richard Henderson (7):
>   exec: Use TARGET_PAGE_BITS_MIN for TLB flags
>   exec: Split out variable page size support to exec-vary.c
>   exec: Use const alias for TARGET_PAGE_BITS_VARY
>   exec: Restrict TARGET_PAGE_BITS_VARY assert to CONFIG_DEBUG_TCG
>   exec: Promote TARGET_PAGE_MASK to target_long
>   exec: Tidy TARGET_PAGE_ALIGN
>   exec: Cache TARGET_PAGE_MASK for TARGET_PAGE_BITS_VARY
> 
>  Makefile.target        |  2 +-
>  include/exec/cpu-all.h | 41 +++++++++++++-------
>  include/qemu-common.h  |  6 +++
>  exec-vary.c            | 88 ++++++++++++++++++++++++++++++++++++++++++
>  exec.c                 | 34 ----------------
>  5 files changed, 123 insertions(+), 48 deletions(-)
>  create mode 100644 exec-vary.c
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Re: [PATCH 0/7] exec: Improve code for TARGET_PAGE_BITS_VARY

[no-reply]

Patchew URL: https://patchew.org/QEMU/20190919232952.6382-1-richard.henderson@linaro.org/



Hi,

This series seems to have some coding style problems. See output below for
more information:

Message-id: 20190919232952.6382-1-richard.henderson@linaro.org
Subject: [PATCH 0/7] exec: Improve code for TARGET_PAGE_BITS_VARY
Type: series

=== TEST SCRIPT BEGIN ===
#!/bin/bash
git rev-parse base > /dev/null || exit 0
git config --local diff.renamelimit 0
git config --local diff.renames True
git config --local diff.algorithm histogram
./scripts/checkpatch.pl --mailback base..
=== TEST SCRIPT END ===

From https://github.com/patchew-project/qemu
 * [new tag]         patchew/20190919232952.6382-1-richard.henderson@linaro.org -> patchew/20190919232952.6382-1-richard.henderson@linaro.org
Switched to a new branch 'test'
02b5da1 exec: Cache TARGET_PAGE_MASK for TARGET_PAGE_BITS_VARY
a7aca78 exec: Tidy TARGET_PAGE_ALIGN
daeccb0 exec: Promote TARGET_PAGE_MASK to target_long
265eec7 exec: Restrict TARGET_PAGE_BITS_VARY assert to CONFIG_DEBUG_TCG
583a7ed exec: Use const alias for TARGET_PAGE_BITS_VARY
a2dd788 exec: Split out variable page size support to exec-vary.c
cc49c84 exec: Use TARGET_PAGE_BITS_MIN for TLB flags

=== OUTPUT BEGIN ===
1/7 Checking commit cc49c847ff45 (exec: Use TARGET_PAGE_BITS_MIN for TLB flags)
2/7 Checking commit a2dd788d074f (exec: Split out variable page size support to exec-vary.c)
WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?
#32: 
new file mode 100644

total: 0 errors, 1 warnings, 125 lines checked

Patch 2/7 has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.
3/7 Checking commit 583a7eda4f9e (exec: Use const alias for TARGET_PAGE_BITS_VARY)
ERROR: externs should be avoided in .c files
#58: FILE: exec-vary.c:53:
+extern const TargetPageBits target_page

total: 1 errors, 0 warnings, 82 lines checked

Patch 3/7 has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.

4/7 Checking commit 265eec7a4f93 (exec: Restrict TARGET_PAGE_BITS_VARY assert to CONFIG_DEBUG_TCG)
5/7 Checking commit daeccb050033 (exec: Promote TARGET_PAGE_MASK to target_long)
6/7 Checking commit a7aca78b21b7 (exec: Tidy TARGET_PAGE_ALIGN)
7/7 Checking commit 02b5da125937 (exec: Cache TARGET_PAGE_MASK for TARGET_PAGE_BITS_VARY)
=== OUTPUT END ===

Test command exited with code: 1


The full log is available at
http://patchew.org/logs/20190919232952.6382-1-richard.henderson@linaro.org/testing.checkpatch/?type=message.
---
Email generated automatically by Patchew [https://patchew.org/].
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Re: [PATCH 2/7] exec: Split out variable page size support to exec-vary.c

[Philippe Mathieu-Daudé]

On 9/20/19 1:29 AM, Richard Henderson wrote:
> The next patch will play a trick with "const" that will
> confuse the compiler about the uses of target_page_bits
> within exec.c.  Moving everything to a new file prevents
> this confusion.
> 
> No functional change so far.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  Makefile.target       |  2 +-
>  include/qemu-common.h |  6 +++++
>  exec-vary.c           | 57 +++++++++++++++++++++++++++++++++++++++++++
>  exec.c                | 34 --------------------------
>  4 files changed, 64 insertions(+), 35 deletions(-)
>  create mode 100644 exec-vary.c
> 
> diff --git a/Makefile.target b/Makefile.target
> index 5e916230c4..ca3d14efe1 100644
> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -107,7 +107,7 @@ obj-y += trace/
>  
>  #########################################################
>  # cpu emulator library
> -obj-y += exec.o
> +obj-y += exec.o exec-vary.o
>  obj-y += accel/
>  obj-$(CONFIG_TCG) += tcg/tcg.o tcg/tcg-op.o tcg/tcg-op-vec.o tcg/tcg-op-gvec.o
>  obj-$(CONFIG_TCG) += tcg/tcg-common.o tcg/optimize.o
> diff --git a/include/qemu-common.h b/include/qemu-common.h
> index 0235cd3b91..3e800c2224 100644
> --- a/include/qemu-common.h
> +++ b/include/qemu-common.h
> @@ -74,6 +74,12 @@ void cpu_exec_step_atomic(CPUState *cpu);
>   */
>  bool set_preferred_target_page_bits(int bits);
>  
> +/**
> + * finalize_target_page_bits:
> + * Commit the final value set by set_preferred_target_page_bits.
> + */
> +void finalize_target_page_bits(void);
> +
>  /**
>   * Sends a (part of) iovec down a socket, yielding when the socket is full, or
>   * Receives data into a (part of) iovec from a socket,
> diff --git a/exec-vary.c b/exec-vary.c
> new file mode 100644
> index 0000000000..48c0ab306c
> --- /dev/null
> +++ b/exec-vary.c
> @@ -0,0 +1,57 @@
> +/*
> + * Variable page size handling
> + *
> + *  Copyright (c) 2003 Fabrice Bellard
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu-common.h"
> +#include "exec/exec-all.h"
> +
> +#ifdef TARGET_PAGE_BITS_VARY
> +int target_page_bits;
> +bool target_page_bits_decided;
> +#endif
> +
> +bool set_preferred_target_page_bits(int bits)
> +{
> +    /*
> +     * The target page size is the lowest common denominator for all
> +     * the CPUs in the system, so we can only make it smaller, never
> +     * larger. And we can't make it smaller once we've committed to
> +     * a particular size.
> +     */
> +#ifdef TARGET_PAGE_BITS_VARY
> +    assert(bits >= TARGET_PAGE_BITS_MIN);
> +    if (target_page_bits == 0 || target_page_bits > bits) {
> +        if (target_page_bits_decided) {
> +            return false;
> +        }
> +        target_page_bits = bits;
> +    }
> +#endif
> +    return true;
> +}
> +
> +void finalize_target_page_bits(void)
> +{
> +#ifdef TARGET_PAGE_BITS_VARY
> +    if (target_page_bits == 0) {
> +        target_page_bits = TARGET_PAGE_BITS_MIN;
> +    }
> +    target_page_bits_decided = true;
> +#endif
> +}
> diff --git a/exec.c b/exec.c
> index 8b998974f8..33bd0e36c1 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -92,11 +92,6 @@ MemoryRegion io_mem_rom, io_mem_notdirty;
>  static MemoryRegion io_mem_unassigned;
>  #endif
>  
> -#ifdef TARGET_PAGE_BITS_VARY
> -int target_page_bits;
> -bool target_page_bits_decided;
> -#endif
> -
>  CPUTailQ cpus = QTAILQ_HEAD_INITIALIZER(cpus);
>  
>  /* current CPU in the current thread. It is only valid inside
> @@ -110,37 +105,8 @@ int use_icount;
>  uintptr_t qemu_host_page_size;
>  intptr_t qemu_host_page_mask;
>  
> -bool set_preferred_target_page_bits(int bits)
> -{
> -    /* The target page size is the lowest common denominator for all
> -     * the CPUs in the system, so we can only make it smaller, never
> -     * larger. And we can't make it smaller once we've committed to
> -     * a particular size.
> -     */
> -#ifdef TARGET_PAGE_BITS_VARY
> -    assert(bits >= TARGET_PAGE_BITS_MIN);
> -    if (target_page_bits == 0 || target_page_bits > bits) {
> -        if (target_page_bits_decided) {
> -            return false;
> -        }
> -        target_page_bits = bits;
> -    }
> -#endif
> -    return true;
> -}
> -
>  #if !defined(CONFIG_USER_ONLY)
>  
> -static void finalize_target_page_bits(void)
> -{
> -#ifdef TARGET_PAGE_BITS_VARY
> -    if (target_page_bits == 0) {
> -        target_page_bits = TARGET_PAGE_BITS_MIN;
> -    }
> -    target_page_bits_decided = true;
> -#endif
> -}
> -
>  typedef struct PhysPageEntry PhysPageEntry;
>  
>  struct PhysPageEntry {
> 

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Re: [PATCH 4/7] exec: Restrict TARGET_PAGE_BITS_VARY assert to CONFIG_DEBUG_TCG

[Philippe Mathieu-Daudé]

On 9/20/19 1:29 AM, Richard Henderson wrote:
> This reduces the size of a release build by about 10k.
> Noticably, within the tlb miss helpers.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/exec/cpu-all.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
> index a53b761b48..b11ee1f711 100644
> --- a/include/exec/cpu-all.h
> +++ b/include/exec/cpu-all.h
> @@ -215,7 +215,11 @@ typedef struct {
>      int bits;
>  } TargetPageBits;
>  extern const TargetPageBits target_page;
> -#define TARGET_PAGE_BITS (assert(target_page.decided), target_page.bits)
> +# ifdef CONFIG_DEBUG_TCG
> +#  define TARGET_PAGE_BITS (assert(target_page.decided), target_page.bits)
> +# else
> +#  define TARGET_PAGE_BITS target_page.bits
> +# endif
>  #else
>  #define TARGET_PAGE_BITS_MIN TARGET_PAGE_BITS
>  #endif
> 

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>