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Smith" , =?utf-8?q?Marek_Marczy?= =?utf-8?q?kowski-G=C3=B3recki?= , Roger Pau Monne , Andrew Cooper , Jan Beulich , Julien Grall , Stefano Stabellini Subject: [PATCH v4 5/6] x86/time: introduce command line option to select wallclock Date: Wed, 4 Sep 2024 17:31:50 +0200 Message-ID: <20240904153151.83995-6-roger.pau@citrix.com> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240904153151.83995-1-roger.pau@citrix.com> References: <20240904153151.83995-1-roger.pau@citrix.com> MIME-Version: 1.0 Allow setting the used wallclock from the command line. When the option is set to a value different than `auto` the probing is bypassed and the selected implementation is used (as long as it's available). The `xen` and `efi` options require being booted as a Xen guest (with Xen guest supported built-in) or from UEFI firmware. Signed-off-by: Roger Pau Monné --- Changes since v3: - Note xen option is only available if Xen guest support it built. - Fix typo. --- docs/misc/xen-command-line.pandoc | 19 ++++++++++++++++++ xen/arch/x86/time.c | 33 ++++++++++++++++++++++++++++++- 2 files changed, 51 insertions(+), 1 deletion(-) diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc index 0a66e1ee2d7e..1944b9d8eb9d 100644 --- a/docs/misc/xen-command-line.pandoc +++ b/docs/misc/xen-command-line.pandoc @@ -2821,6 +2821,25 @@ vwfi to `native` reduces irq latency significantly. It can also lead to suboptimal scheduling decisions, but only when the system is oversubscribed (i.e., in total there are more vCPUs than pCPUs). +### wallclock (x86) +> `= auto | xen | cmos | efi` + +> Default: `auto` + +Allow forcing the usage of a specific wallclock source. + + * `auto` let the hypervisor select the clocksource based on internal + heuristics. + + * `xen` force usage of the Xen shared_info wallclock when booted as a Xen + guest. This option is only available if the hypervisor was compiled with + `CONFIG_XEN_GUEST` enabled. + + * `cmos` force usage of the CMOS RTC wallclock. + + * `efi` force usage of the EFI_GET_TIME run-time method when booted from EFI + firmware. + ### watchdog (x86) > `= force | ` diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c index 9ebeee61b987..52944b8fbfde 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -1553,6 +1553,36 @@ static const char *__init wallclock_type_to_string(void) return ""; } +static int __init cf_check parse_wallclock(const char *arg) +{ + if ( !arg ) + return -EINVAL; + + if ( !strcmp("auto", arg) ) + wallclock_source = WALLCLOCK_UNSET; + else if ( !strcmp("xen", arg) ) + { + if ( !xen_guest ) + return -EINVAL; + + wallclock_source = WALLCLOCK_XEN; + } + else if ( !strcmp("cmos", arg) ) + wallclock_source = WALLCLOCK_CMOS; + else if ( !strcmp("efi", arg) ) + { + if ( !efi_enabled(EFI_RS) ) + return -EINVAL; + + wallclock_source = WALLCLOCK_EFI; + } + else + return -EINVAL; + + return 0; +} +custom_param("wallclock", parse_wallclock); + static void __init probe_wallclock(void) { ASSERT(wallclock_source == WALLCLOCK_UNSET); @@ -2528,7 +2558,8 @@ int __init init_xen_time(void) open_softirq(TIME_CALIBRATE_SOFTIRQ, local_time_calibration); - probe_wallclock(); + if ( wallclock_source == WALLCLOCK_UNSET ) + probe_wallclock(); printk(XENLOG_INFO "Wallclock source: %s\n", wallclock_type_to_string());