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[174.21.143.238]) by smtp.gmail.com with ESMTPSA id m1sm9290690pjy.0.2020.07.11.14.42.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 11 Jul 2020 14:42:23 -0700 (PDT) Subject: Re: [PATCH v2 01/17] tcg: Introduce target-specific page data for user-only To: Peter Maydell References: <20200605041733.415188-1-richard.henderson@linaro.org> <20200605041733.415188-2-richard.henderson@linaro.org> From: Richard Henderson Message-ID: Date: Sat, 11 Jul 2020 14:42:21 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::1042; envelope-from=richard.henderson@linaro.org; helo=mail-pj1-x1042.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. 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=unavailable autolearn_force=no X-Spam_action: no action 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: qemu-arm , QEMU Developers , Stephen Long Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/25/20 9:20 AM, Peter Maydell wrote: > On Fri, 5 Jun 2020 at 05:17, Richard Henderson > wrote: >> >> This data can be allocated by page_alloc_target_data() and >> released by page_set_flags(start, end, prot | PAGE_RESET). >> >> This data will be used to hold tag memory for AArch64 MTE. >> >> Signed-off-by: Richard Henderson >> --- > >> @@ -289,6 +295,8 @@ int walk_memory_regions(void *, walk_memory_regions_fn); >> int page_get_flags(target_ulong address); >> void page_set_flags(target_ulong start, target_ulong end, int flags); >> int page_check_range(target_ulong start, target_ulong len, int flags); >> +void *page_get_target_data(target_ulong address); >> +void *page_alloc_target_data(target_ulong address, size_t size); > > Could we have a doc comment for any new function that's got > global scope, please? > >> #endif >> >> CPUArchState *cpu_copy(CPUArchState *env); > >> +void *page_alloc_target_data(target_ulong address, size_t size) >> +{ >> + PageDesc *p = page_find(address >> TARGET_PAGE_BITS); >> + void *ret = NULL; >> + >> + if (p) { >> + ret = p->target_data; >> + if (!ret && (p->flags & PAGE_VALID)) { >> + p->target_data = ret = g_malloc0(size); >> + } >> + } >> + return ret; > > Can a PageDesc validly have p->target_data != NULL but > p->flags with PAGE_VALID not set ? No. But we can be called for a page that is not mapped (returning NULL) and can be called for a page that already has associated data (returning the old value). > It's not clear to me why for a !PAGE_VALID page which > has target_data already we return that pointer but > if it doesn't have any we don't allocate: either > "always allocate" or "always return NULL for non-valid pages" > would seem more self-consistent. I was expecting a non-valid page to have no data. I will rearrange this to ret = NULL; if (p->flags & PAGE_VALID) { ret = p->target_data; if (!ret) { p->target_data = ret = g_malloc0(size); } } which is probably clearer. >> + /* FIXME: Move page flags and target_data for each page. */ > > Is this something we're going to address later in the patchset? I had not, but I should. Will fix. r~