linux-kernel - Re: [PATCH v2 03/36] irqchip/gic-v3-its: Allow LPI invalidation via the DirectLPI interface

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Message-ID: <a263e264-298c-57cf-31b7-a781160a3929@huawei.com>
Date:   Thu, 31 Oct 2019 16:49:32 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     Marc Zyngier <maz@...nel.org>, <kvmarm@...ts.cs.columbia.edu>,
        <linux-kernel@...r.kernel.org>
CC:     Eric Auger <eric.auger@...hat.com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "Andrew Murray" <Andrew.Murray@....com>,
        Jayachandran C <jnair@...vell.com>,
        "Robert Richter" <rrichter@...vell.com>
Subject: Re: [PATCH v2 03/36] irqchip/gic-v3-its: Allow LPI invalidation via
 the DirectLPI interface

Hi Marc,

On 2019/10/27 22:42, Marc Zyngier wrote:
> We currently don't make much use of the DirectLPI feature, and it would
> be beneficial to do this more, if only because it becomes a mandatory
> feature for GICv4.1.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>

I have no objection to this patch, which says:

Reviewed-by: Zenghui Yu <yuzenghui@...wei.com>

But this patch really drives me to look through all callsites of
dev_event_to_col(), the abstraction which can be used _only_ with
physical LPI mappings.

I find that when building the INV command, we use dev_event_to_col()
to find the "sync_obj" and then pass it to the following SYNC command.
But the "INV+SYNC" will be performed both on physical LPI and *VLPI*
(lpi_update_config/its_send_inv).
So I have two questions about the way we sending INV on VLPI:

1) Which "sync" command should be followed?  SYNC or VSYNC?
(we currently use SYNC, while the spec says, SYNC "ensures all
outstanding ITS operations associated with *physical* interrupts
for the Redistributor are globally observed ...")

2) The "sync_obj" we are currently using seems to be wrong.

Thanks,
Zenghui