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target/loongarch: Reduce TLB flush with helper_tlbwr

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With function helper_tlbwr(), specified LoongArch TLB entry will be
updated. There are two PTE pages in one TLB entry called even/odd
pages. Supposing even/odd page is normal/none state, when odd page
is added, TLB entry is changed as normal/normal state and even page
keeps unchanged.

In this situation, it is not necessary to flush QEMU TLB since even
page keep unchanged and odd page is newly changed. Here check whether
PTE page is the same or not, TLB flush can be skipped if both are the
same or newly added.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Bibo Mao 2025-07-24 20:34:35 +08:00
parent 5a1d5dbccc
commit 8fa3df9833
1 changed files with 24 additions and 5 deletions
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29
target/loongarch/tcg/tlb_helper.c
View file

@ -302,16 +302,35 @@ void helper_tlbrd(CPULoongArchState *env)
void helper_tlbwr(CPULoongArchState *env)
{
int index = FIELD_EX64(env->CSR_TLBIDX, CSR_TLBIDX, INDEX);
LoongArchTLB *old, new = {};
bool skip_inv = false;
uint8_t tlb_v0, tlb_v1;
invalidate_tlb(env, index);
old = env->tlb + index;
if (FIELD_EX64(env->CSR_TLBIDX, CSR_TLBIDX, NE)) {
env->tlb[index].tlb_misc = FIELD_DP64(env->tlb[index].tlb_misc,
TLB_MISC, E, 0);
invalidate_tlb(env, index);
old->tlb_misc = FIELD_DP64(old->tlb_misc, TLB_MISC, E, 0);
return;
}
fill_tlb_entry(env, env->tlb + index);
fill_tlb_entry(env, &new);
/* Check whether ASID/VPPN is the same */
if (old->tlb_misc == new.tlb_misc) {
/* Check whether both even/odd pages is the same or invalid */
tlb_v0 = FIELD_EX64(old->tlb_entry0, TLBENTRY, V);
tlb_v1 = FIELD_EX64(old->tlb_entry1, TLBENTRY, V);
if ((!tlb_v0 || new.tlb_entry0 == old->tlb_entry0) &&
(!tlb_v1 || new.tlb_entry1 == old->tlb_entry1)) {
skip_inv = true;
}
}
/* flush tlb before updating the entry */
if (!skip_inv) {
invalidate_tlb(env, index);
}
*old = new;
}
void helper_tlbfill(CPULoongArchState *env)