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[93.51.222.138]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b0416842ffasm910351366b.38.2025.09.03.06.08.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Sep 2025 06:08:00 -0700 (PDT) Message-ID: Date: Wed, 3 Sep 2025 15:07:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 03/12] target/loongarch: Reduce TLB flush with helper_tlbwr To: Bibo Mao , Song Gao , =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= Cc: Jiaxun Yang , qemu-devel@nongnu.org References: <20250903084827.3085911-1-maobibo@loongson.cn> <20250903084827.3085911-4-maobibo@loongson.cn> From: Richard Henderson Content-Language: en-US In-Reply-To: <20250903084827.3085911-4-maobibo@loongson.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2a00:1450:4864:20::62a; envelope-from=richard.henderson@linaro.org; helo=mail-ej1-x62a.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 9/3/25 10:48, Bibo Mao wrote: > 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 > --- > target/loongarch/tcg/tlb_helper.c | 33 ++++++++++++++++++++++++++----- > 1 file changed, 28 insertions(+), 5 deletions(-) > > diff --git a/target/loongarch/tcg/tlb_helper.c b/target/loongarch/tcg/tlb_helper.c > index fcd03ca320..331b485b1a 100644 > --- a/target/loongarch/tcg/tlb_helper.c > +++ b/target/loongarch/tcg/tlb_helper.c > @@ -302,16 +302,39 @@ void helper_tlbrd(CPULoongArchState *env) > void helper_tlbwr(CPULoongArchState *env) > { > int index = FIELD_EX64(env->CSR_TLBIDX, CSR_TLBIDX, INDEX); > + LoongArchTLB *old, new; Perhaps "new = { }", then ... > + new.tlb_misc = 0; > + new.tlb_entry0 = 0; > + new.tlb_entry1 = 0; ... this is unnecessary. > + 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->tlb_misc = new.tlb_misc; > + old->tlb_entry0 = new.tlb_entry0; > + old->tlb_entry1 = new.tlb_entry1; Perhaps better as "*old = new". Anyway, Reviewed-by: Richard Henderson r~