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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.

Reviewed-by: Aaron Lindsay <aaron@os.amperecomputing.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20181019015617.22583-3-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Richard Henderson 2018-10-24 07:50:20 +01:00 committed by Peter Maydell
parent f478847f1e
commit 93f379b0c4
1 changed files with 3 additions and 5 deletions
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8
target/arm/helper.c
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@ -2758,12 +2758,10 @@ 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);