linux-kernel - Re: [patch 33/33] irqchip: Add IDXD Interrupt Message Store driver

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Message-ID: <d85d91f2-25e7-f706-094b-56c417becf1c@intel.com>
Date:   Fri, 2 Dec 2022 13:16:47 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
CC:     <x86@...nel.org>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>, <linux-pci@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "Marc Zyngier" <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Alex Williamson" <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Ashok Raj <ashok.raj@...el.com>, Jon Mason <jdmason@...zu.us>,
        Allen Hubbe <allenbh@...il.com>,
        "Ahmed S. Darwish" <darwi@...utronix.de>
Subject: Re: [patch 33/33] irqchip: Add IDXD Interrupt Message Store driver

Hi Thomas,

On 12/2/2022 11:51 AM, Thomas Gleixner wrote:
> On Fri, Dec 02 2022 at 09:55, Reinette Chatre wrote:
>> On 11/11/2022 5:59 AM, Thomas Gleixner wrote:

>> @@ -33,6 +34,8 @@ struct ims_slot {
>>  #define CTRL_PASID_ENABLE	BIT(3)
>>  /* Position of PASID.LSB in the control word */
>>  #define CTRL_PASID_SHIFT	12
>> +/* Valid PASID is 20 bits */
>> +#define CTRL_PASID_VALID	GENMASK(19, 0)
>>  
>>  static inline void iowrite32_and_flush(u32 value, void __iomem *addr)
>>  {
>> @@ -93,12 +96,17 @@ static void idxd_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
>>  	/* Mask the interrupt for paranoia sake */
>>  	iowrite32_and_flush(CTRL_VECTOR_MASKBIT, &slot->ctrl);
>>  
>> -	/*
>> -	 * The caller provided PASID. Shift it to the proper position
>> -	 * and set the PASID enable bit.
>> -	 */
>> -	desc->data.icookie.value <<= CTRL_PASID_SHIFT;
>> -	desc->data.icookie.value |= CTRL_PASID_ENABLE;
>> +	if (pasid_valid((ioasid_t)desc->data.icookie.value)) {
>> +		/*
>> +		 * The caller provided PASID. Shift it to the proper position
>> +		 * and set the PASID enable bit.
>> +		 */
>> +		desc->data.icookie.value &= CTRL_PASID_VALID;
>> +		desc->data.icookie.value <<= CTRL_PASID_SHIFT;
>> +		desc->data.icookie.value |= CTRL_PASID_ENABLE;
>> +	} else {
>> +		desc->data.icookie.value = 0;
>> +	}
> 
> Looks about right. But that needs some sanity measures at the call sites
> so that we don't end up with an invalid PASID in cases where a valid
> PASID is truly required.

I will take a closer look at this. Current call site is explicit to
set an invalid PASID when PASID use is disabled. I still need to do testing
with valid PASID to learn those flows.

Reinette