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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 v6 1/2] x86/time: introduce command line option to select wallclock Date: Thu, 12 Sep 2024 13:15:13 +0200 Message-ID: <20240912111514.26934-2-roger.pau@citrix.com> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240912111514.26934-1-roger.pau@citrix.com> References: <20240912111514.26934-1-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 respectively. Signed-off-by: Roger Pau Monné --- Changes since v5: - Do EFI run-time services checking after command line parsing. 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 | 39 ++++++++++++++++++++++++++++++- 2 files changed, 57 insertions(+), 1 deletion(-) diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc index 959cf45b55d9..a4f916d0d33e 100644 --- a/docs/misc/xen-command-line.pandoc +++ b/docs/misc/xen-command-line.pandoc @@ -2816,6 +2816,25 @@ 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 9588502f28e8..b97c81ebd3e9 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -1552,6 +1552,35 @@ 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) ) + /* + * Checking if run-time services are available must be done after + * command line parsing. + */ + 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); @@ -2527,7 +2556,15 @@ int __init init_xen_time(void) open_softirq(TIME_CALIBRATE_SOFTIRQ, local_time_calibration); - probe_wallclock(); + /* + * EFI run time services can be disabled from the command line, hence the + * check for them cannot be done as part of the wallclock option parsing. + */ + if ( wallclock_source == WALLCLOCK_EFI && !efi_enabled(EFI_RS) ) + wallclock_source = WALLCLOCK_UNSET; + + if ( wallclock_source == WALLCLOCK_UNSET ) + probe_wallclock(); printk(XENLOG_INFO "Wallclock source: %s\n", wallclock_type_to_string());