linux-kernel - Re: [RFC PATCH] vfio/pci: Add ioeventfd support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180206212538.50ef0e13@w520.home>
Date:   Tue, 6 Feb 2018 21:25:38 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        qemu-devel@...gnu.org
Subject: Re: [RFC PATCH] vfio/pci: Add ioeventfd support

On Wed, 7 Feb 2018 15:09:22 +1100
Alexey Kardashevskiy <aik@...abs.ru> wrote:
> On 07/02/18 11:08, Alex Williamson wrote:
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index e3301dbd27d4..07966a5f0832 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -503,6 +503,30 @@ struct vfio_pci_hot_reset {
> >  
> >  #define VFIO_DEVICE_PCI_HOT_RESET	_IO(VFIO_TYPE, VFIO_BASE + 13)
> >  
> > +/**
> > + * VFIO_DEVICE_IOEVENTFD - _IOW(VFIO_TYPE, VFIO_BASE + 14,
> > + *                              struct vfio_device_ioeventfd)
> > + *
> > + * Perform a write to the device at the specified device fd offset, with
> > + * the specified data and width when the provided eventfd is triggered.
> > + *
> > + * Return: 0 on success, -errno on failure.
> > + */
> > +struct vfio_device_ioeventfd {
> > +	__u32	argsz;
> > +	__u32	flags;
> > +#define VFIO_DEVICE_IOEVENTFD_8		(1 << 0) /* 1-byte write */
> > +#define VFIO_DEVICE_IOEVENTFD_16	(1 << 1) /* 2-byte write */
> > +#define VFIO_DEVICE_IOEVENTFD_32	(1 << 2) /* 4-byte write */
> > +#define VFIO_DEVICE_IOEVENTFD_64	(1 << 3) /* 8-byte write */
> > +#define VFIO_DEVICE_IOEVENTFD_SIZE_MASK	(0xf)
> > +	__u64	offset;			/* device fd offset of write */
> > +	__u64	data;			/* data to be written */
> > +	__s32	fd;			/* -1 for de-assignment */
> > +};
> > +
> > +#define VFIO_DEVICE_IOEVENTFD		_IO(VFIO_TYPE, VFIO_BASE + 14)  
> 
> 
> Is this a first ioctl with endianness fixed to little-endian? I'd suggest
> to comment on that as things like vfio_info_cap_header do use the host
> endianness.

Look at our current read and write interface, we call leXX_to_cpu
before calling iowriteXX there and I think a user would logically
expect to use the same data format here as they would there.  Also note
that iowriteXX does a cpu_to_leXX, so are we really defining the
interface as little-endian or are we just trying to make ourselves
endian neutral and counter that implicit conversion?  Thanks,

Alex