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([38.41.223.211]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7482b0c0613sm7864225b3a.122.2025.06.10.14.28.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Jun 2025 14:28:48 -0700 (PDT) From: Pierrick Bouvier To: qemu-devel@nongnu.org Cc: philmd@linaro.org, berrange@redhat.com, peter.maydell@linaro.org, =?utf-8?q?Alex_Benn=C3=A9e?= , richard.henderson@linaro.org, Thomas Huth , Paolo Bonzini , Pierrick Bouvier Subject: [PATCH 2/2] system/rtc: introduce -rtc time-dilation option Date: Tue, 10 Jun 2025 14:28:29 -0700 Message-ID: <20250610212829.2818792-3-pierrick.bouvier@linaro.org> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250610212829.2818792-1-pierrick.bouvier@linaro.org> References: <20250610212829.2818792-1-pierrick.bouvier@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::431; envelope-from=pierrick.bouvier@linaro.org; helo=mail-pf1-x431.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 This option sets a factor on time spent for QEMU clocks since the beginning of execution. It can be used to slow or accelerate time for a guest, without impacting QEMU speed. Signed-off-by: Pierrick Bouvier --- system/rtc.c | 11 +++++++++++ system/vl.c | 3 +++ qemu-options.hx | 7 ++++++- 3 files changed, 20 insertions(+), 1 deletion(-) diff --git a/system/rtc.c b/system/rtc.c index 56951288c40..36c53f0fbd7 100644 --- a/system/rtc.c +++ b/system/rtc.c @@ -188,4 +188,15 @@ void configure_rtc(QemuOpts *opts) exit(1); } } + value = qemu_opt_get(opts, "time-dilation"); + if (value) { + if (qemu_strtod_finite(value, NULL, &clock_time_dilation)) { + error_report("invalid time-dilation factor '%s'", value); + exit(1); + } + if (clock_time_dilation <= 0.0f) { + error_report("time-dilation factor must be strictly positive"); + exit(1); + } + } } diff --git a/system/vl.c b/system/vl.c index 3b7057e6c66..e3e3f2f0209 100644 --- a/system/vl.c +++ b/system/vl.c @@ -243,6 +243,9 @@ static QemuOptsList qemu_rtc_opts = { },{ .name = "driftfix", .type = QEMU_OPT_STRING, + },{ + .name = "time-dilation", + .type = QEMU_OPT_STRING, }, { /* end of list */ } }, diff --git a/qemu-options.hx b/qemu-options.hx index 4faad5604c0..b8aaf8b3349 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -4887,7 +4887,7 @@ SRST ERST DEF("rtc", HAS_ARG, QEMU_OPTION_rtc, \ - "-rtc [base=utc|localtime|][,clock=host|rt|vm][,driftfix=none|slew]\n" \ + "-rtc [base=utc|localtime|][,clock=host|rt|vm][,driftfix=none|slew][,time-dilation=value]\n" \ " set the RTC base and clock, enable drift fix for clock ticks (x86 only)\n", QEMU_ARCH_ALL) @@ -4916,6 +4916,11 @@ SRST problems, specifically with Windows' ACPI HAL. This option will try to figure out how many timer interrupts were not processed by the Windows guest and will re-inject them. + + It's possible to slow or accelerate time using ``time-dilation``, + which is a factor (real number) applied to QEMU clock. A value of 0.1 will + slow time by a factor of 10, and a value of 10 will accelerate it with the + same factor. ERST DEF("icount", HAS_ARG, QEMU_OPTION_icount, \