linux-kernel - Re: [PATCH v5 02/12] x86/paravirt: switch time pvops functions to use static

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Date:   Tue, 9 Mar 2021 07:14:37 +0100
From:   Jürgen Groß <jgross@...e.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, x86@...nel.org,
        virtualization@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org, kvm@...r.kernel.org
Cc:     Deep Shah <sdeep@...are.com>,
        "VMware, Inc." <pv-drivers@...are.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Stefano Stabellini <sstabellini@...nel.org>
Subject: Re: [PATCH v5 02/12] x86/paravirt: switch time pvops functions to use
 static_call()

On 08.03.21 18:00, Boris Ostrovsky wrote:
> 
> On 3/8/21 7:28 AM, Juergen Gross wrote:
>> --- a/arch/x86/xen/time.c
>> +++ b/arch/x86/xen/time.c
>> @@ -379,11 +379,6 @@ void xen_timer_resume(void)
>>   	}
>>   }
>>   
>> -static const struct pv_time_ops xen_time_ops __initconst = {
>> -	.sched_clock = xen_sched_clock,
>> -	.steal_clock = xen_steal_clock,
>> -};
>> -
>>   static struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
>>   static u64 xen_clock_value_saved;
>>   
>> @@ -528,7 +523,8 @@ static void __init xen_time_init(void)
>>   void __init xen_init_time_ops(void)
>>   {
>>   	xen_sched_clock_offset = xen_clocksource_read();
>> -	pv_ops.time = xen_time_ops;
>> +	static_call_update(pv_steal_clock, xen_steal_clock);
>> +	paravirt_set_sched_clock(xen_sched_clock);
>>   
>>   	x86_init.timers.timer_init = xen_time_init;
>>   	x86_init.timers.setup_percpu_clockev = x86_init_noop;
>> @@ -570,7 +566,8 @@ void __init xen_hvm_init_time_ops(void)
>>   	}
>>   
>>   	xen_sched_clock_offset = xen_clocksource_read();
>> -	pv_ops.time = xen_time_ops;
>> +	static_call_update(pv_steal_clock, xen_steal_clock);
>> +	paravirt_set_sched_clock(xen_sched_clock);
>>   	x86_init.timers.setup_percpu_clockev = xen_time_init;
>>   	x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;
> 
> 
> There is a bunch of stuff that's common between the two cases so it can be factored out.

Yes.

> 
> 
>>   
>> diff --git a/drivers/xen/time.c b/drivers/xen/time.c
>> index 108edbcbc040..152dd33bb223 100644
>> --- a/drivers/xen/time.c
>> +++ b/drivers/xen/time.c
>> @@ -7,6 +7,7 @@
>>   #include <linux/math64.h>
>>   #include <linux/gfp.h>
>>   #include <linux/slab.h>
>> +#include <linux/static_call.h>
>>   
>>   #include <asm/paravirt.h>
>>   #include <asm/xen/hypervisor.h>
>> @@ -175,7 +176,7 @@ void __init xen_time_setup_guest(void)
>>   	xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
>>   					VMASST_TYPE_runstate_update_flag);
>>   
>> -	pv_ops.time.steal_clock = xen_steal_clock;
>> +	static_call_update(pv_steal_clock, xen_steal_clock);
>>   
> 
> 
> Do we actually need this? We've already set this up in xen_init_time_ops(). (But maybe for ARM).

Correct. Arm needs this.


Juergen

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