From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yuanhan Liu Subject: Re: [ [PATCH v2] 05/13] virtio: change io_base datatype from uint32_t to uint64_type Date: Wed, 16 Dec 2015 22:58:46 +0800 Message-ID: <20151216145846.GX29571@yliu-dev.sh.intel.com> References: <1450098032-21198-1-git-send-email-sshukla@mvista.com> <1450098032-21198-6-git-send-email-sshukla@mvista.com> <20151216134850.GU29571@yliu-dev.sh.intel.com> <20151216142326.GV29571@yliu-dev.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: dev@dpdk.org To: Santosh Shukla Return-path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 1EEC45A51 for ; Wed, 16 Dec 2015 15:58:38 +0100 (CET) Content-Disposition: inline In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Wed, Dec 16, 2015 at 08:09:40PM +0530, Santosh Shukla wrote: > On Wed, Dec 16, 2015 at 7:53 PM, Yuanhan Liu > wrote: > > On Wed, Dec 16, 2015 at 07:31:57PM +0530, Santosh Shukla wrote: > >> On Wed, Dec 16, 2015 at 7:18 PM, Yuanhan Liu > >> wrote: > >> > On Mon, Dec 14, 2015 at 06:30:24PM +0530, Santosh Shukla wrote: > >> >> In x86 case io_base to store ioport address not more than 65535 ioports. i.e..0 > >> >> to ffff but in non-x86 case in particular arm64 it need to store more than 32 > >> >> bit address so changing io_base datatype from 32 to 64. > >> >> > >> >> Signed-off-by: Santosh Shukla > >> >> --- > >> >> drivers/net/virtio/virtio_ethdev.c | 2 +- > >> >> drivers/net/virtio/virtio_pci.h | 4 ++-- > >> >> 2 files changed, 3 insertions(+), 3 deletions(-) > >> >> > >> >> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c > >> >> index d928339..620e0d4 100644 > >> >> --- a/drivers/net/virtio/virtio_ethdev.c > >> >> +++ b/drivers/net/virtio/virtio_ethdev.c > >> >> @@ -1291,7 +1291,7 @@ eth_virtio_dev_init(struct rte_eth_dev *eth_dev) > >> >> return -1; > >> >> > >> >> hw->use_msix = virtio_has_msix(&pci_dev->addr); > >> >> - hw->io_base = (uint32_t)(uintptr_t)pci_dev->mem_resource[0].addr; > >> >> + hw->io_base = (uint64_t)(uintptr_t)pci_dev->mem_resource[0].addr; > >> > > >> > I'd suggest to move the io_base assignment (and cast) into virtio_ioport_init() > >> > so that we could do the correct cast there, say cast it to uint32_t for > >> > X86, and uint64_t for others. > >> > > >> > >> Ok. > >> > >> This was deliberately done considering your 1.0 virtio spec patch do > >> care for uint64_t types and in arm64 case, If I plan to use those > >> future patches, IMO it make more sense to me keep it in uint64_t way; > > > > I did different cast, 32 bit for legacy virtio pci device, and 64 bit > > for modern virtio pci device. > > > >> Also in x86 case max address could of type 0x1000-101f and so forth; > >> changing data-type to uint64_t default wont effect such address, > >> right? > > > > Right, but what's the harm of doing the right cast? :) > > > > Agree. > > >> And hw->io_base by looking at virtio_pci.h function like > >> inb/outb etc.. takes io_base address as unsigned long types which is > >> arch dependent; i.e.. 4 byte for 32 bit and 8 for 64 bit so the lower > >> level rd/wr apis are taking care of data-types accordingly. > > > > Didn't get it. inb/outb takes "unsigned short" arguments, but not > > "unsigned long". > > > > sys/io.h in x86 case using unsigned short int types.. > > include/asm-generic/io.h for arm64 using it unsigned long (from linux > header files) > > In such case keeping > #define VIRTIO_PCI_REG_ADDR(hw, reg) \ > (unsigned short)((hw)->io_base + (reg)) > > would be x86 specific and what I thought and used in this patch is > > #define VIRTIO_PCI_REG_ADDR(hw, reg) \ > (unsigned long)((hw)->io_base + (reg)) > > to avoid ifdef ARM or non-x86..clutter, I know data-type is not right > fit for x86 sys/io.h but considering possible address inside > hw->io_base, wont effect functionality and performance my any mean. > That is why at virtio_ethdev_init() i choose to keep it in hw->io_base > = (uint64_t) types. > > Otherwise I'll have to duplicate VIRTIO_PCI_REG_XXX definition for > non-x86 case, Pl. suggest better alternative. Thanks My understanding is that if you have done the right cast in the first time (at the io_base assignment), casting from a short type to a longer type will not matter: the upper bits will be filled with zero. So, I guess we are fine here. I'm thinking that the extra cast in VIRTIO_PCI_REG_ADDR() is not necessary, as C will do the right cast for different inb(), say cast it to "unsigned short" for x86, and "unsigned long" for your arm implementation. The same to other io helpers. --yliu