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authorRichard Henderson <richard.henderson@linaro.org>2018-10-18 18:56:16 -0700
committerPeter Maydell <peter.maydell@linaro.org>2018-10-19 17:38:48 +0100
commit88c9add25e7120e8622796c81ad3f3fb7f8d40e7 (patch)
tree33b613d88a75d5ec431b0a2b663eb9b4f4a15ac8
parent5b67106992e2a829119a7902925d6b79cab4ad14 (diff)
downloadqemu-arm-target-arm.for-upstream.tar.gz
target/arm: Only flush tlb if ASID changespull-target-arm-20181019target-arm.nexttarget-arm.for-upstream
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>
-rw-r--r--target/arm/helper.c8
1 files changed, 3 insertions, 5 deletions
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 20114bf574..bea4d5350d 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -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);