From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Lu Baolu <baolu.lu@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Ingo Molnar <mingo@redhat.com>
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>,
tglx@linutronix.de, peterz@infradead.org,
linux-usb@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org, Juergen Gross <jgross@suse.com>,
xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH v8 1/5] x86: add simple udelay calibration
Date: Tue, 2 May 2017 18:38:39 -0400 [thread overview]
Message-ID: <d0d66c8d-b731-14ff-c8c8-e67c6391efcc@oracle.com> (raw)
In-Reply-To: <1490083293-3792-2-git-send-email-baolu.lu@linux.intel.com>
On 03/21/2017 04:01 AM, Lu Baolu wrote:
> Add a simple udelay calibration in x86 architecture-specific
> boot-time initializations. This will get a workable estimate
> for loops_per_jiffy. Hence, udelay() could be used after this
> initialization.
This breaks Xen PV guests since at this point, and until
x86_init.paging.pagetable_init() which is when pvclock_vcpu_time_info is
mapped, they cannot access pvclock.
Is it reasonable to do this before tsc_init() is called? (The failure
has nothing to do with tsc_init(), really --- it's just that it is
called late enough that Xen PV guests get properly initialized.) If it
is, would it be possible to move simple_udelay_calibration() after
x86_init.paging.pagetable_init()?
-boris
>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: x86@kernel.org
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> arch/x86/kernel/setup.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 4bf0c89..e70204e 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -837,6 +837,26 @@ dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
> return 0;
> }
>
> +static void __init simple_udelay_calibration(void)
> +{
> + unsigned int tsc_khz, cpu_khz;
> + unsigned long lpj;
> +
> + if (!boot_cpu_has(X86_FEATURE_TSC))
> + return;
> +
> + cpu_khz = x86_platform.calibrate_cpu();
> + tsc_khz = x86_platform.calibrate_tsc();
> +
> + tsc_khz = tsc_khz ? : cpu_khz;
> + if (!tsc_khz)
> + return;
> +
> + lpj = tsc_khz * 1000;
> + do_div(lpj, HZ);
> + loops_per_jiffy = lpj;
> +}
> +
> /*
> * Determine if we were loaded by an EFI loader. If so, then we have also been
> * passed the efi memmap, systab, etc., so we should use these data structures
> @@ -985,6 +1005,8 @@ void __init setup_arch(char **cmdline_p)
> */
> x86_configure_nx();
>
> + simple_udelay_calibration();
> +
> parse_early_param();
>
> #ifdef CONFIG_MEMORY_HOTPLUG
next prev parent reply other threads:[~2017-05-02 22:40 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-21 8:01 [PATCH v8 0/5] usb: early: add support for early printk through USB3 debug port Lu Baolu
2017-03-21 8:01 ` [PATCH v8 1/5] x86: add simple udelay calibration Lu Baolu
2017-03-21 12:19 ` [tip:x86/debug] x86/timers: Add " tip-bot for Lu Baolu
2017-05-24 16:56 ` Jan Kiszka
2017-05-25 0:49 ` Lu Baolu
2017-05-02 22:38 ` Boris Ostrovsky [this message]
2017-05-05 5:41 ` [PATCH v8 1/5] x86: add " Lu Baolu
2017-05-05 12:50 ` Boris Ostrovsky
2017-07-12 8:02 ` Dou Liyang
2017-07-13 1:17 ` Lu Baolu
2017-07-13 1:39 ` Dou Liyang
2017-07-13 3:00 ` Lu Baolu
2017-07-14 3:21 ` Dou Liyang
2017-03-21 8:01 ` [PATCH v8 2/5] usb: early: add driver for xhci debug capability Lu Baolu
2017-03-21 12:19 ` [tip:x86/debug] usb/early: Add " tip-bot for Lu Baolu
2017-05-30 13:46 ` [PATCH v8 2/5] usb: early: add " Vlastimil Babka
2017-05-31 3:27 ` Lu Baolu
2017-05-31 6:24 ` Steven Rostedt
2017-06-01 3:35 ` Lu Baolu
2017-05-31 9:38 ` Vlastimil Babka
2017-06-01 3:37 ` Lu Baolu
2017-06-01 8:15 ` Vlastimil Babka
2017-06-01 12:25 ` Peter Zijlstra
2017-06-02 0:47 ` Steven Rostedt
2017-03-21 8:01 ` [PATCH v8 3/5] x86: add support for earlyprintk via USB3 debug port Lu Baolu
2017-03-21 12:20 ` [tip:x86/debug] x86/earlyprintk: Add " tip-bot for Lu Baolu
2017-03-21 8:01 ` [PATCH v8 4/5] usb: serial: add dbc debug device support to usb_debug Lu Baolu
2017-03-21 12:21 ` [tip:x86/debug] usb/serial: Add DBC " tip-bot for Lu Baolu
2017-03-21 8:01 ` [PATCH v8 5/5] usb: doc: add document for USB3 debug port usage Lu Baolu
2017-03-21 12:21 ` [tip:x86/debug] usb/doc: Add " tip-bot for Lu Baolu
2017-03-21 11:33 ` [PATCH v8 0/5] usb: early: add support for early printk through USB3 debug port Ingo Molnar
2017-03-21 12:27 ` Greg Kroah-Hartman
2017-03-21 12:46 ` Ingo Molnar
2017-03-22 2:23 ` Lu Baolu
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