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Subject: Re: x86/ioapic: Cleanup the timer_works() irqflags mess
To:     Thomas Gleixner <tglx@linutronix.de>,
        Mark Rutland <mark.rutland@arm.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        xen-devel@lists.xenproject.org, x86@kernel.org,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org, luto@kernel.org,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Deep Shah <sdeep@vmware.com>,
        "VMware, Inc." <pv-drivers@vmware.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Stefano Stabellini <sstabellini@kernel.org>
References: <20201120114630.13552-1-jgross@suse.com>
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 <87tusuzu71.fsf@nanos.tec.linutronix.de>
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From:   =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= <jgross@suse.com>
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Date:   Fri, 11 Dec 2020 06:10:42 +0100
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From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= <jgross@suse.com>
To: Thomas Gleixner <tglx@linutronix.de>, Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>, xen-devel@lists.xenproject.org,
 x86@kernel.org, linux-kernel@vger.kernel.org,
 virtualization@lists.linux-foundation.org, luto@kernel.org,
 Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
 "H. Peter Anvin" <hpa@zytor.com>, Deep Shah <sdeep@vmware.com>,
 "VMware, Inc." <pv-drivers@vmware.com>,
 Boris Ostrovsky <boris.ostrovsky@oracle.com>,
 Stefano Stabellini <sstabellini@kernel.org>
Message-ID: <0a90cfff-05d6-1475-43f8-e41b5af24281@suse.com>
Subject: Re: x86/ioapic: Cleanup the timer_works() irqflags mess
References: <20201120114630.13552-1-jgross@suse.com>
 <20201120114630.13552-6-jgross@suse.com>
 <20201120115943.GD3021@hirez.programming.kicks-ass.net>
 <20201209181514.GA14235@C02TD0UTHF1T.local>
 <87tusuzu71.fsf@nanos.tec.linutronix.de>
 <20201210111008.GB88655@C02TD0UTHF1T.local>
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In-Reply-To: <87k0tpju47.fsf@nanos.tec.linutronix.de>

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On 10.12.20 21:15, Thomas Gleixner wrote:
> Mark tripped over the creative irqflags handling in the IO-APIC timer
> delivery check which ends up doing:
>=20
>          local_irq_save(flags);
> 	local_irq_enable();
>          local_irq_restore(flags);
>=20
> which triggered a new consistency check he's working on required for
> replacing the POPF based restore with a conditional STI.
>=20
> That code is a historical mess and none of this is needed. Make it
> straightforward use local_irq_disable()/enable() as that's all what is
> required. It is invoked from interrupt enabled code nowadays.
>=20
> Reported-by: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Tested-by: Mark Rutland <mark.rutland@arm.com>

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

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