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target/arm: Only flush tlb if ASID changes

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Since QEMU does not implement ASIDs, changes to the ASID must flush the
tlb. However, if the ASID does not change there is no reason to flush.

In testing a boot of the Ubuntu installer to the first menu, this reduces
the number of flushes by 30%, or nearly 600k instances.

Backports commit 93f379b0c43617b1361f742f261479eaed4959cb from qemu
This commit is contained in:
Richard Henderson 2018-11-10 11:26:22 -05:00 committed by Lioncash
parent 15a6b3f771
commit e9fe7d3c8d
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GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 3 additions and 5 deletions
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8
qemu/target/arm/helper.c
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@ -2448,12 +2448,10 @@ static void vmsa_tcr_el1_write(CPUARMState *env, const ARMCPRegInfo *ri,
static void vmsa_ttbr_write(CPUARMState *env, const ARMCPRegInfo *ri,
uint64_t value)
{
/* 64 bit accesses to the TTBRs can change the ASID and so we
* must flush the TLB.
*/
if (cpreg_field_is_64bit(ri)) {
/* If the ASID changes (with a 64-bit write), we must flush the TLB. */
if (cpreg_field_is_64bit(ri) &&
extract64(raw_read(env, ri) ^ value, 48, 16) != 0) {
ARMCPU *cpu = arm_env_get_cpu(env);
tlb_flush(CPU(cpu));
}
raw_write(env, ri, value);