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[97.113.7.119]) by smtp.gmail.com with ESMTPSA id x26sm92220455pfq.69.2019.08.01.11.37.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Aug 2019 11:37:43 -0700 (PDT) To: Aaron Lindsay OS , =?UTF-8?Q?Alex_Benn=c3=a9e?= References: <20190731160719.11396-1-alex.bennee@linaro.org> <20190731160719.11396-25-alex.bennee@linaro.org> <20190801141431.GK5034@quinoa.localdomain> From: Richard Henderson Openpgp: preference=signencrypt Message-ID: <7d4d47c9-c1ac-5778-35a6-8aa3174a302a@linaro.org> Date: Thu, 1 Aug 2019 11:37:41 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190801141431.GK5034@quinoa.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::543 Subject: Re: [Qemu-devel] [PATCH v4 24/54] plugins: implement helpers for resolving hwaddr X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , "bobby.prani@gmail.com" , "cota@braap.org" , "qemu-devel@nongnu.org" , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/1/19 7:14 AM, Aaron Lindsay OS via Qemu-devel wrote: > On Jul 31 17:06, Alex Bennée wrote: >> We need to keep a local per-cpu copy of the data as other threads may >> be running. We use a automatically growing array and re-use the space >> for subsequent queries. > > [...] > >> +bool tlb_plugin_lookup(CPUState *cpu, target_ulong addr, int mmu_idx, >> + bool is_store, struct qemu_plugin_hwaddr *data) >> +{ >> + CPUArchState *env = cpu->env_ptr; >> + CPUTLBEntry *tlbe = tlb_entry(env, mmu_idx, addr); >> + target_ulong tlb_addr = is_store ? tlb_addr_write(tlbe) : tlbe->addr_read; >> + >> + if (tlb_hit(tlb_addr, addr)) { >> + if (tlb_addr & TLB_MMIO) { >> + data->hostaddr = 0; >> + data->is_io = true; >> + /* XXX: lookup device */ >> + } else { >> + data->hostaddr = addr + tlbe->addend; >> + data->is_io = false; >> + } >> + return true; >> + } >> + return false; >> +} > > In what cases do you expect tlb_hit() should not evaluate to true here? > Will returns of false only be in error cases, or do you expect it can > occur during normal operation? In particular, I'm interested in ensuring > this is as reliable as possible, since some plugins may require physical > addresses. I have the same question. Given the access has just succeeded, it would seem to be that the tlb entry *must* hit. No victim tlb check or anything. r~