From: Alexey Kardashevskiy <aik@ozlabs.ru> To: Alex Williamson <alex.williamson@redhat.com> Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org Subject: Re: [RFC PATCH] vfio/pci: Add ioeventfd support Date: Wed, 7 Feb 2018 15:48:26 +1100 [thread overview] Message-ID: <6014d60c-9bdb-4dc0-7cd7-9299005d9c5a@ozlabs.ru> (raw) In-Reply-To: <20180206212538.50ef0e13@w520.home> On 07/02/18 15:25, Alex Williamson wrote: > On Wed, 7 Feb 2018 15:09:22 +1100 > Alexey Kardashevskiy <aik@ozlabs.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. If the data is "char data[8]" (i.e. bytestream), then it can be expected to be device/bus endian (i.e. PCI == little endian), but if it is u64 - then I am not so sure really, and this made me look around. It could be "__le64 data" too. > 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, Defining it LE is fine, I just find it a bit confusing when vfio_info_cap_header is host endian but vfio_device_ioeventfd is not. -- Alexey
WARNING: multiple messages have this Message-ID (diff)
From: Alexey Kardashevskiy <aik@ozlabs.ru> To: Alex Williamson <alex.williamson@redhat.com> Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org Subject: Re: [Qemu-devel] [RFC PATCH] vfio/pci: Add ioeventfd support Date: Wed, 7 Feb 2018 15:48:26 +1100 [thread overview] Message-ID: <6014d60c-9bdb-4dc0-7cd7-9299005d9c5a@ozlabs.ru> (raw) In-Reply-To: <20180206212538.50ef0e13@w520.home> On 07/02/18 15:25, Alex Williamson wrote: > On Wed, 7 Feb 2018 15:09:22 +1100 > Alexey Kardashevskiy <aik@ozlabs.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. If the data is "char data[8]" (i.e. bytestream), then it can be expected to be device/bus endian (i.e. PCI == little endian), but if it is u64 - then I am not so sure really, and this made me look around. It could be "__le64 data" too. > 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, Defining it LE is fine, I just find it a bit confusing when vfio_info_cap_header is host endian but vfio_device_ioeventfd is not. -- Alexey
next prev parent reply other threads:[~2018-02-07 4:48 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-02-07 0:08 [RFC PATCH] vfio/pci: Add ioeventfd support Alex Williamson 2018-02-07 0:08 ` [Qemu-devel] " Alex Williamson 2018-02-07 4:09 ` Alexey Kardashevskiy 2018-02-07 4:09 ` [Qemu-devel] " Alexey Kardashevskiy 2018-02-07 4:25 ` Alex Williamson 2018-02-07 4:25 ` [Qemu-devel] " Alex Williamson 2018-02-07 4:48 ` Alexey Kardashevskiy [this message] 2018-02-07 4:48 ` Alexey Kardashevskiy 2018-02-07 14:12 ` Alex Williamson 2018-02-07 14:12 ` [Qemu-devel] " Alex Williamson 2018-02-08 1:22 ` Alexey Kardashevskiy 2018-02-08 1:22 ` [Qemu-devel] " Alexey Kardashevskiy 2018-03-13 12:38 ` Auger Eric 2018-03-13 12:38 ` [Qemu-devel] " Auger Eric 2018-03-15 21:23 ` Alex Williamson 2018-03-15 21:23 ` [Qemu-devel] " Alex Williamson 2018-02-07 15:46 ` Auger Eric 2018-02-07 16:57 ` Alex Williamson 2018-02-08 13:48 ` Auger Eric 2018-02-09 7:05 ` Peter Xu 2018-02-09 21:45 ` Alex Williamson 2018-02-11 3:09 ` Peter Xu
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