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From: Dmitry Safonov <dima@arista.com>
To: Lu Baolu <baolu.lu@linux.intel.com>,
	linux-kernel@vger.kernel.org, joro@8bytes.org, "Raj,
	Ashok" <ashok.raj@intel.com>
Cc: 0x7f454c46@gmail.com,
	Alex Williamson <alex.williamson@redhat.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	iommu@lists.linux-foundation.org
Subject: Re: [PATCHv4 2/2] iommu/vt-d: Limit number of faults to clear in irq handler
Date: Thu, 03 May 2018 02:59:36 +0100	[thread overview]
Message-ID: <1525312776.14025.29.camel@arista.com> (raw)
In-Reply-To: <5AEA66BC.5050202@linux.intel.com>

On Thu, 2018-05-03 at 09:32 +0800, Lu Baolu wrote:
> Hi,
> 
> On 05/03/2018 08:52 AM, Dmitry Safonov wrote:
> > AFAICS, we're doing fault-clearing in a loop inside irq handler.
> > That means that while we're clearing if a fault raises, it'll make
> > an irq level triggered (or on edge) on lapic. So, whenever we
> > return
> > from the irq handler, irq will raise again.
> > 
> 
> Uhm, double checked with the spec. Interrupts should be generated
> since we always clear the fault overflow bit.
> 
> Anyway, we can't clear faults in a limited loop, as the spec says in
> 7.3.1:

Mind to elaborate?
ITOW, I do not see a contradiction. We're still clearing faults in FIFO
fashion. There is no limitation to do some spare work in between
clearings (return from interrupt, then fault again and continue).

> Software is expected to process the non-recoverable faults reported
> through the Fault Recording
> Registers in a circular FIFO fashion starting from the Fault
> Recording Register referenced by the Fault
> Recording Index (FRI) field, until it finds a Fault Recording
> Register with no faults (F field Clear).
> 
> Best regards,
> Lu Baolu

-- 
Thanks,
             Dmitry

  reply	other threads:[~2018-05-03  1:59 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-31  0:33 [PATCHv4 1/2] iommu/vt-d: Ratelimit each dmar fault printing Dmitry Safonov
2018-03-31  0:33 ` [PATCHv4 2/2] iommu/vt-d: Limit number of faults to clear in irq handler Dmitry Safonov
2018-05-02  6:34   ` Lu Baolu
2018-05-02 12:38     ` Dmitry Safonov
2018-05-02 23:49       ` Lu Baolu
2018-05-03  0:52         ` Dmitry Safonov
2018-05-03  1:32           ` Lu Baolu
2018-05-03  1:59             ` Dmitry Safonov [this message]
2018-05-03  2:16               ` Lu Baolu
2018-05-03  2:32                 ` Lu Baolu
2018-05-03  2:34                 ` Dmitry Safonov
2018-05-03  2:44                   ` Lu Baolu
2018-05-02  2:22 ` [PATCHv4 1/2] iommu/vt-d: Ratelimit each dmar fault printing Dmitry Safonov
2018-05-03 12:40   ` Joerg Roedel
2018-05-03 16:12     ` Dmitry Safonov

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