On Thu, 16 May 2019 17:36:43 +0100 Bruce Richardson <bruce.richard...@intel.com> wrote:
> On Thu, May 16, 2019 at 05:07:45PM +0100, Bruce Richardson wrote: > > On Thu, May 16, 2019 at 09:06:52AM -0700, Stephen Hemminger wrote: > > > On Thu, 16 May 2019 17:03:37 +0100 > > > Bruce Richardson <bruce.richard...@intel.com> wrote: > > > > > > > On Wed, May 15, 2019 at 03:19:52PM -0700, Stephen Hemminger wrote: > > > > > Using bit operations like or and xor is faster than a loop > > > > > on all architectures. Really just explicit unrolling. > > > > > > > > > > Similar cast to uint16 unaligned is already done in > > > > > other functions here. > > > > > > > > > > Signed-off-by: Stephen Hemminger <step...@networkplumber.org> > > > > > --- > > > > > lib/librte_net/rte_ether.h | 17 +++++++---------- > > > > > 1 file changed, 7 insertions(+), 10 deletions(-) > > > > > > > > > Rather than casting to unaligned values, which gives compiler warnings > > > > in > > > > some cases, I believe we should just mark the ethernet addresses as > > > > always > > > > being 2-byte aligned and simplify things. [unless we have a good use > > > > case > > > > where we won't have 2-byte alignment???]. > > > > > > > > See patch: http://patches.dpdk.org/patch/53482/ > > > > > > > > Regards, > > > > /Bruce > > > > > > I agree. Then you could also remove the unaligned_uint16_t that > > > already exists in rte_ether.h > > > > > > Do you want me to put your patch in my series? > > > > Sure, feel free. > > > > I've just found another problem in this area. Compiling l2fwd with gcc 9, I > get: > > main.c:164:54: warning: taking address of packed member of ‘struct ether_hdr’ > may result in an unaligned pointer value [-Waddress-of-packed-member] > 164 | ether_addr_copy(&l2fwd_ports_eth_addr[dest_portid], ð->s_addr); > | > > Looking at some of the structures, it appears that not all the packet > attributes may be necessary. For example, while AFAIK there are not > absolute guarantees about structure padding, for all compilers I remember > using the following changes are safe: > > diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h > index 8090b7c01..7d9f34791 100644 > --- a/lib/librte_net/rte_ether.h > +++ b/lib/librte_net/rte_ether.h > @@ -57,7 +57,7 @@ extern "C" { > struct ether_addr { > /** Addr bytes in tx order */ > uint8_t addr_bytes[ETHER_ADDR_LEN] __rte_aligned(2); > -} __attribute__((__packed__)); > +}; > > #define ETHER_LOCAL_ADMIN_ADDR 0x02 /**< Locally assigned Eth. address. */ > #define ETHER_GROUP_ADDR 0x01 /**< Multicast or broadcast Eth. > address. */ > @@ -273,7 +273,7 @@ struct ether_hdr { > struct ether_addr d_addr; /**< Destination address. */ > struct ether_addr s_addr; /**< Source address. */ > uint16_t ether_type; /**< Frame type. */ > -} __attribute__((__packed__)); > +}; > > /** > * Ethernet VLAN Header. > @@ -283,7 +283,7 @@ struct ether_hdr { > struct vlan_hdr { > uint16_t vlan_tci; /**< Priority (3) + CFI (1) + Identifier Code (12) > */ > uint16_t eth_proto;/**< Ethernet type of encapsulated frame. */ > -} __attribute__((__packed__)); > +}; > > /** > * VXLAN protocol header. > > I think we therefore should consider removing those packed attributes to > avoid application warnings. > > /Bruce Agree if structure is naturally packed, adding packed attribute is a mistake.
