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

From: Abhishek Sahu <abhsahu@nvidia.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Yishai Hadas <yishaih@nvidia.com>,
	Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
	Kevin Tian <kevin.tian@intel.com>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Max Gurtovoy <mgurtovoy@nvidia.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	linux-pm@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH v3 8/8] vfio/pci: Add the support for PCI D3cold state
Date: Thu, 12 May 2022 17:57:05 +0530	[thread overview]
Message-ID: <fdba8dd2-4db8-81f3-d9d8-4742c88e99d9@nvidia.com> (raw)
In-Reply-To: <20220510133041.GA49344@nvidia.com>

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