qemu/include/exec/page-vary.h

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/*
* Definitions for cpus with variable page sizes.
*
* 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 2.1 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/>.
*/
#ifndef EXEC_PAGE_VARY_H
#define EXEC_PAGE_VARY_H
typedef struct {
bool decided;
int bits;
uint64_t mask;
} TargetPageBits;
exec: Build page-vary-common.c with -fno-lto In bbc17caf81f, we used an alias attribute to allow target_page to be declared const, and yet be initialized late. This fails when using LTO with several versions of gcc. The compiler looks through the alias and decides that the const variable is statically initialized to zero, then propagates that zero to many uses of the variable. This can be avoided by compiling one object file with -fno-lto. In this way, any initializer cannot be seen, and the constant propagation does not occur. Since we are certain to have this separate compilation unit, we can drop the alias attribute as well. We simply have differing declarations for target_page in different compilation units. Drop the use of init_target_page, and drop the configure detection for CONFIG_ATTRIBUTE_ALIAS. In order to change the compilation flags for a file with meson, we must use a static_library. This runs into specific_ss, where we would need to create many static_library instances. Fix this by splitting page-vary.c: the page-vary-common.c part is compiled once as a static_library, while the page-vary.c part is left in specific_ss in order to handle the target-specific value of TARGET_PAGE_BITS_MIN. Reported-by: Gavin Shan <gshan@redhat.com> Signed-off-by: Richard Henderson <richard.henderson@linaro.org> Message-Id: <20210321211534.2101231-1-richard.henderson@linaro.org> [PMD: Fix typo in subject, split original patch in 3] Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Tested-by: Gavin Shan <gshan@redhat.com> Message-Id: <20210322112427.4045204-4-f4bug@amsat.org> [rth: Update MAINTAINERS] Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2021-03-22 14:24:26 +03:00
#ifdef IN_PAGE_VARY
extern bool set_preferred_target_page_bits_common(int bits);
extern void finalize_target_page_bits_common(int min);
#endif
/**
* set_preferred_target_page_bits:
* @bits: number of bits needed to represent an address within the page
*
* Set the preferred target page size (the actual target page
* size may be smaller than any given CPU's preference).
* Returns true on success, false on failure (which can only happen
* if this is called after the system has already finalized its
* choice of page size and the requested page size is smaller than that).
*/
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);
#endif /* EXEC_PAGE_VARY_H */