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[76.14.210.194]) by smtp.gmail.com with ESMTPSA id x185-20020a6286c2000000b0056bfebfa6e4sm12586151pfd.190.2022.12.29.16.06.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Dec 2022 16:06:05 -0800 (PST) From: Richard Henderson To: qemu-devel@nongnu.org Cc: =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= Subject: [PULL 46/47] accel/tcg: Handle false negative lookup in page_check_range Date: Thu, 29 Dec 2022 16:02:20 -0800 Message-Id: <20221230000221.2764875-47-richard.henderson@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20221230000221.2764875-1-richard.henderson@linaro.org> References: <20221230000221.2764875-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::52b; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x52b.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+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org As in page_get_flags, we need to try again with the mmap lock held if we fail a page lookup. Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Richard Henderson --- accel/tcg/user-exec.c | 41 ++++++++++++++++++++++++++++++++++------- 1 file changed, 34 insertions(+), 7 deletions(-) diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c index 2c5c10d2e6..a8eb63ab96 100644 --- a/accel/tcg/user-exec.c +++ b/accel/tcg/user-exec.c @@ -525,6 +525,8 @@ void page_set_flags(target_ulong start, target_ulong end, int flags) int page_check_range(target_ulong start, target_ulong len, int flags) { target_ulong last; + int locked; /* tri-state: =0: unlocked, +1: global, -1: local */ + int ret; if (len == 0) { return 0; /* trivial length */ @@ -535,42 +537,67 @@ int page_check_range(target_ulong start, target_ulong len, int flags) return -1; /* wrap around */ } + locked = have_mmap_lock(); while (true) { PageFlagsNode *p = pageflags_find(start, last); int missing; if (!p) { - return -1; /* entire region invalid */ + if (!locked) { + /* + * Lockless lookups have false negatives. + * Retry with the lock held. + */ + mmap_lock(); + locked = -1; + p = pageflags_find(start, last); + } + if (!p) { + ret = -1; /* entire region invalid */ + break; + } } if (start < p->itree.start) { - return -1; /* initial bytes invalid */ + ret = -1; /* initial bytes invalid */ + break; } missing = flags & ~p->flags; if (missing & PAGE_READ) { - return -1; /* page not readable */ + ret = -1; /* page not readable */ + break; } if (missing & PAGE_WRITE) { if (!(p->flags & PAGE_WRITE_ORG)) { - return -1; /* page not writable */ + ret = -1; /* page not writable */ + break; } /* Asking about writable, but has been protected: undo. */ if (!page_unprotect(start, 0)) { - return -1; + ret = -1; + break; } /* TODO: page_unprotect should take a range, not a single page. */ if (last - start < TARGET_PAGE_SIZE) { - return 0; /* ok */ + ret = 0; /* ok */ + break; } start += TARGET_PAGE_SIZE; continue; } if (last <= p->itree.last) { - return 0; /* ok */ + ret = 0; /* ok */ + break; } start = p->itree.last + 1; } + + /* Release the lock if acquired locally. */ + if (locked < 0) { + mmap_unlock(); + } + return ret; } void page_protect(tb_page_addr_t address)