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target/arm: arm_pamax() no longer needs to do feature propagation

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In arm_pamax(), we need to cope with the virt board calling this
function on a CPU object which has been inited but not realize.
We used to do propagation of feature-flag implications (such as
"V7VE implies LPAE") at realize, so we have some code in arm_pamax()
which manually checks for both V7VE and LPAE feature flags.

In commit b8f7959f28 we moved the feature propagation for
almost all features from realize to post-init. That means that
now when the virt board calls arm_pamax(), the feature propagation
has been done. So we can drop the manual propagation handling
and check only for the feature we actually care about, which
is ARM_FEATURE_LPAE.

Retain the comment that the virt board is calling this function
with a not completely realized CPU object, because that is a
potential beartrap for later changes which is worth calling out.

(Note that b8f7959f28 actually fixed a bug in the arm_pamax()
handling: arm_pamax() was missing a check for ARM_FEATURE_V8, so it
incorrectly thought that the qemu-system-arm 'max' CPU did not have
LPAE and turned off 'highmem' support in the virt board.  Following
b8f7959f28 qemu-system-arm 'max' is treated the same as
'cortex-a15' and other v7 LPAE CPUs, because the generic feature
propagation code does correctly propagate V8 -> V7VE -> LPAE.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240109143804.1118307-1-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2024-01-09 14:38:04 +00:00
parent d95f260aee
commit 71e269fb7b
1 changed files with 6 additions and 8 deletions
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14
target/arm/ptw.c
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@ -95,7 +95,10 @@ static const uint8_t pamax_map[] = {
[6] = 52,
};
/* The cpu-specific constant value of PAMax; also used by hw/arm/virt. */
/*
* The cpu-specific constant value of PAMax; also used by hw/arm/virt.
* Note that machvirt_init calls this on a CPU that is inited but not realized!
*/
unsigned int arm_pamax(ARMCPU *cpu)
{
if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
@ -110,13 +113,8 @@ unsigned int arm_pamax(ARMCPU *cpu)
return pamax_map[parange];
}
/*
* In machvirt_init, we call arm_pamax on a cpu that is not fully
* initialized, so we can't rely on the propagation done in realize.
*/
if (arm_feature(&cpu->env, ARM_FEATURE_LPAE) ||
arm_feature(&cpu->env, ARM_FEATURE_V7VE)) {
/* v7 with LPAE */
if (arm_feature(&cpu->env, ARM_FEATURE_LPAE)) {
/* v7 or v8 with LPAE */
return 40;
}
/* Anything else */