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Fri, 13 Sep 2024 00:59:18 -0700 (PDT) From: Roger Pau Monne To: xen-devel@lists.xenproject.org Cc: "Daniel P. Smith" , =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?= , Roger Pau Monne , Andrew Cooper , Jan Beulich , Julien Grall , Stefano Stabellini Subject: [PATCH v7 1/2] x86/time: introduce command line option to select wallclock Date: Fri, 13 Sep 2024 09:59:06 +0200 Message-ID: <20240913075907.34460-2-roger.pau@citrix.com> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240913075907.34460-1-roger.pau@citrix.com> References: <20240913075907.34460-1-roger.pau@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @citrix.com) X-ZM-MESSAGEID: 1726214387735116600 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 g= uest supported built-in) or from UEFI firmware respectively. Signed-off-by: Roger Pau Monn=C3=A9 --- Changes since v6: - Clarify documentation regarding repeated using of the wallclock command = line option. 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 | 21 ++++++++++++++++ xen/arch/x86/time.c | 41 ++++++++++++++++++++++++++++++- 2 files changed, 61 insertions(+), 1 deletion(-) diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line= .pandoc index 959cf45b55d9..2a9b3b9b8975 100644 --- a/docs/misc/xen-command-line.pandoc +++ b/docs/misc/xen-command-line.pandoc @@ -2816,6 +2816,27 @@ 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). =20 +### wallclock (x86) +> `=3D auto |=C2=A0xen | 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 wi= th + `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. + +If the selected option is invalid or not available Xen will default to `au= to`. + ### watchdog (x86) > `=3D force | ` =20 diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c index 29b026735e5d..e4751684951e 100644 --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -1552,6 +1552,37 @@ static const char *__init wallclock_type_to_string(v= oid) return ""; } =20 +static int __init cf_check parse_wallclock(const char *arg) +{ + wallclock_source =3D WALLCLOCK_UNSET; + + if ( !arg ) + return -EINVAL; + + if ( !strcmp("auto", arg) ) + ASSERT(wallclock_source =3D=3D WALLCLOCK_UNSET); + else if ( !strcmp("xen", arg) ) + { + if ( !xen_guest ) + return -EINVAL; + + wallclock_source =3D WALLCLOCK_XEN; + } + else if ( !strcmp("cmos", arg) ) + wallclock_source =3D WALLCLOCK_CMOS; + else if ( !strcmp("efi", arg) ) + /* + * Checking if run-time services are available must be done after + * command line parsing. + */ + wallclock_source =3D WALLCLOCK_EFI; + else + return -EINVAL; + + return 0; +} +custom_param("wallclock", parse_wallclock); + static void __init probe_wallclock(void) { ASSERT(wallclock_source =3D=3D WALLCLOCK_UNSET); @@ -2527,7 +2558,15 @@ int __init init_xen_time(void) =20 open_softirq(TIME_CALIBRATE_SOFTIRQ, local_time_calibration); =20 - 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 parsi= ng. + */ + if ( wallclock_source =3D=3D WALLCLOCK_EFI && !efi_enabled(EFI_RS) ) + wallclock_source =3D WALLCLOCK_UNSET; + + if ( wallclock_source =3D=3D WALLCLOCK_UNSET ) + probe_wallclock(); =20 printk(XENLOG_INFO "Wallclock source: %s\n", wallclock_type_to_string(= )); =20 --=20 2.46.0