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target-arm: Make page size a runtime setting 

Rather than defining TARGET_PAGE_BITS to always be 10,
switch to using a value picked at runtime. This allows us
to use 4K pages for modern ARM CPUs (and in particular all
64-bit CPUs) without having to drop support for the old
ARMv5 CPUs which had 1K pages.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Peter Maydell 2016-10-24 16:26:50 +01:00
parent 59811a320d
commit e97da98f11
2 changed files with 29 additions and 4 deletions
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24
target-arm/cpu.c
View File

@ -576,6 +576,7 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
ARMCPU *cpu = ARM_CPU(dev);
ARMCPUClass *acc = ARM_CPU_GET_CLASS(dev);
CPUARMState *env = &cpu->env;
int pagebits;
/* Some features automatically imply others: */
if (arm_feature(env, ARM_FEATURE_V8)) {
@ -631,6 +632,29 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
set_feature(env, ARM_FEATURE_THUMB_DSP);
}
if (arm_feature(env, ARM_FEATURE_V7) &&
!arm_feature(env, ARM_FEATURE_M) &&
!arm_feature(env, ARM_FEATURE_MPU)) {
/* v7VMSA drops support for the old ARMv5 tiny pages, so we
* can use 4K pages.
*/
pagebits = 12;
} else {
/* For CPUs which might have tiny 1K pages, or which have an
* MPU and might have small region sizes, stick with 1K pages.
*/
pagebits = 10;
}
if (!set_preferred_target_page_bits(pagebits)) {
/* This can only ever happen for hotplugging a CPU, or if
* the board code incorrectly creates a CPU which it has
* promised via minimum_page_size that it will not.
*/
error_setg(errp, "This CPU requires a smaller page size than the "
"system is using");
return;
}
if (cpu->reset_hivecs) {
cpu->reset_sctlr |= (1 << 13);
}

9
target-arm/cpu.h
View File

@ -1766,10 +1766,11 @@ bool write_cpustate_to_list(ARMCPU *cpu);
#if defined(CONFIG_USER_ONLY)
#define TARGET_PAGE_BITS 12
#else
/* The ARM MMU allows 1k pages. */
/* ??? Linux doesn't actually use these, and they're deprecated in recent
architecture revisions. Maybe a configure option to disable them. */
#define TARGET_PAGE_BITS 10
/* ARMv7 and later CPUs have 4K pages minimum, but ARMv5 and v6
* have to support 1K tiny pages.
*/
#define TARGET_PAGE_BITS_VARY
#define TARGET_PAGE_BITS_MIN 10
#endif
#if defined(TARGET_AARCH64)