linux-kernel - Re: [PATCH v3 8/8] vfio/pci: Add the support for PCI D3cold state

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Date:   Thu, 12 May 2022 17:57:05 +0530
From:   Abhishek Sahu <abhsahu@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Yishai Hadas <yishaih@...dia.com>,
        Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
        Kevin Tian <kevin.tian@...el.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Max Gurtovoy <mgurtovoy@...dia.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v3 8/8] vfio/pci: Add the support for PCI D3cold state

On 5/10/2022 7:00 PM, Jason Gunthorpe wrote:
> On Tue, May 10, 2022 at 06:56:02PM +0530, Abhishek Sahu wrote:
>>> We can add a directive to enforce an alignment regardless of the field
>>> size.  I believe the feature ioctl header is already going to be eight
>>> byte aligned, so it's probably not strictly necessary, but Jason seems
>>> to be adding more of these directives elsewhere, so probably a good
>>> idea regardless.  Thanks,
> 
>> So, should I change it like
>>
>> __u8    low_power_state __attribute__((aligned(8)));
>>
>>  Or
>>
>> __aligned_u64 low_power_state
> 
> You should be explicit about padding, add a reserved to cover the gap.
> 
> Jasno


 Thanks Jason.

 So, I need to make it like following. Correct ?

 __u8 low_power_state;
 __u8 reserved[7];

 It seems, then this aligned attribute should not be required.

 Thanks,
 Abhishek