Received-SPF: pass (google.com: domain of linux-kernel+bounces-145997-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Date: Mon, 15 Apr 2024 16:20:47 -0700
From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: LKML <linux-kernel@vger.kernel.org>, X86 Kernel <x86@kernel.org>, Peter
 Zijlstra <peterz@infradead.org>, "iommu@lists.linux.dev"
 <iommu@lists.linux.dev>, Thomas Gleixner <tglx@linutronix.de>, Lu Baolu
 <baolu.lu@linux.intel.com>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
 "Hansen, Dave" <dave.hansen@intel.com>, Joerg Roedel <joro@8bytes.org>, "H.
 Peter Anvin" <hpa@zytor.com>, Borislav Petkov <bp@alien8.de>, Ingo Molnar
 <mingo@redhat.com>, "Luse, Paul E" <paul.e.luse@intel.com>, "Williams, Dan
 J" <dan.j.williams@intel.com>, Jens Axboe <axboe@kernel.dk>, "Raj, Ashok"
 <ashok.raj@intel.com>, "maz@kernel.org" <maz@kernel.org>,
 "seanjc@google.com" <seanjc@google.com>, Robin Murphy
 <robin.murphy@arm.com>, "jim.harris@samsung.com" <jim.harris@samsung.com>,
 "a.manzanares@samsung.com" <a.manzanares@samsung.com>, Bjorn Helgaas
 <helgaas@kernel.org>, "Zeng, Guang" <guang.zeng@intel.com>,
 "robert.hoo.linux@gmail.com" <robert.hoo.linux@gmail.com>,
 jacob.jun.pan@linux.intel.com
Subject: Re: [PATCH v2 11/13] iommu/vt-d: Make posted MSI an opt-in cmdline
 option
Message-ID: <20240415162047.34f19b0f@jacob-builder>
In-Reply-To: <BN9PR11MB527627DF2470FEC3144F59B08C042@BN9PR11MB5276.namprd11.prod.outlook.com>
References: <20240405223110.1609888-1-jacob.jun.pan@linux.intel.com>
	<20240405223110.1609888-12-jacob.jun.pan@linux.intel.com>
	<BN9PR11MB527627DF2470FEC3144F59B08C042@BN9PR11MB5276.namprd11.prod.outlook.com>
Organization: OTC
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit

Hi Kevin,

On Fri, 12 Apr 2024 09:31:32 +0000, "Tian, Kevin" <kevin.tian@intel.com>
wrote:

> > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Sent: Saturday, April 6, 2024 6:31 AM
> > 
> > +#ifdef CONFIG_X86_POSTED_MSI
> > +		else if (!strncmp(str, "posted_msi", 10)) {
> > +			if (disable_irq_post || disable_irq_remap)
> > +				pr_warn("Posted MSI not enabled due to
> > conflicting options!");
> > +			else
> > +				enable_posted_msi = 1;
> > +		}
> > +#endif  
> 
> the check of disable_irq_remap is unnecessary. It's unlikely to have
> a configuration with disable_irq_post=0 while disable_irq_remap=1
> given the latter has bigger scope.
> 
> but thinking more do we really need a check here? there is no order
> guarantee that "posted_msi" is parsed after the parameters deciding
> the value of two disable variables.
> 
> it probably makes more sense to just set enable_posted_msi here
> and then do all required checks when picking up the irqchip in
> intel_irq_remapping_alloc().

Makes sense, I have a helper function posted_msi_supported() called in
intel_irq_remapping_alloc() already.

My intention was to alert negligent users, but is is not really necessary
as you said.

Thanks,

Jacob