> -----Original Message-----
> From: Ilya Maximets <[email protected]>
> Sent: Friday 25 November 2022 17:22
> To: Finn, Emma <[email protected]>; [email protected]
> Cc: [email protected]; Eelco Chaudron <[email protected]>
> Subject: Re: [ovs-dev] [v5] odp-execute: Add ISA implementation of
> set_masked IPv6 action
>
> On 11/25/22 17:23, Emma Finn wrote:
> > This commit adds support for the AVX512 implementation of the
> > ipv6_set_addrs action as well as an AVX512 implementation of updating
> > the L4 checksums.
> >
> > Signed-off-by: Emma Finn <[email protected]>
> >
> > ---
> > v5:
> > - Fixed load for ip6 src and dst mask for checksum check.
> > v4:
> > - Reworked and moved check for checksum outside loop.
> > - Code cleanup based on review from Eelco.
> > v3:
> > - Added a runtime check for AVX512 vbmi.
> > v2:
> > - Added check for availbility of s6_addr32 field of struct in6_addr.
> > - Fixed network headers for freebsd builds.
> > ---
> > ---
> > lib/odp-execute-avx512.c | 204
> > ++++++++++++++++++++++++++++++++++++++
> > lib/odp-execute-private.c | 17 ++++
> > lib/odp-execute-private.h | 1 +
> > 3 files changed, 222 insertions(+)
>
> Hi, Emma. Thanks for the patch!
> I didn't review the actual AVX512 code, but I have a couple of questions and
> nits inline.
>
Thanks Ilya.
My replies are inline below.
<SNIP>
> > +
> > +/* This function performs the same operation on each packet in the
> > +batch as
> > + * the scalar odp_set_ipv6() function. */
>
> I'm not sure if that statement is correct. If you'll look at the
> odp_set_ipv6()
> implementation and precisely at the
> packet_set_ipv6() implementation, there is a check for the routing extension
> header combined with the check for the fragmentation header
> (packet_rh_present) to prevent writing into L4 fields that do not exist or, in
> case of routing header being present, checksum should not be updated for
> the destination address.
>
> Could you point me to the AVX512 code that is responsible for that check?
>
I think the AVX code is handling this case the same as scalar and also I cannot
reproduce a failure with the autovalidator.
If I am following the scalar code correctly, you're right. If there is a
routing extension header present, for the dst address no checksum will happen.
But similarly for src address, a checksum won't happen.
As packet_update_csum128() will only do a checksum if ip6_nxt is UPD,TCP or
ICMPv6. Which won't be the case if any extension header is present.
Similarly in the AVX code, l4 checksum will only happen if ip6_nxt is UPD,TCP
or ICMPv6, i.e no extension header is present.
So I think this case is covered if I'm not missing any corner cases?
Have you been able to see a failure with autovalidator ?
> > +static void
> > +__attribute__((__target__("avx512vbmi")))
> > +action_avx512_ipv6_set_addrs(struct dp_packet_batch *batch,
> > + const struct nlattr *a)
>
> Name of a function is a bit confusing. Doesn't it also set tclass, proto,
> etc. ?
>
It does. Would something like action_avx512_set_ipv6() be better?
As the scalar function is called packet_set_ipv6().
> > +{
> > + const struct ovs_key_ipv6 *key, *mask;
> > + struct dp_packet *packet;
> > +
> > + a = nl_attr_get(a);
> > + key = nl_attr_get(a);
> > + mask = odp_get_key_mask(a, struct ovs_key_ipv6);
> > +
> > + /* Read the content of the key and mask in the respective registers. We
> > + * only load the size of the actual structure, which is only 40 bytes.
> > */
> > + __m512i v_key = _mm512_maskz_loadu_epi64(0x1F, (void *) key);
> > + __m512i v_mask = _mm512_maskz_loadu_epi64(0x1F, (void *) mask);
> > +
> > + /* This shuffle mask v_shuffle, is to shuffle key and mask to match the
> > + * ip6_hdr structure layout. */
> > + static const uint8_t ip_shuffle_mask[64] = {
> > + 0x20, 0x21, 0x22, 0x23, 0xFF, 0xFF, 0x24, 0x26,
> > + 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
> > + 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
> > + 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
> > + 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F,
> > + 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0XFF, 0xFF, 0xFF,
> > + 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
> > + 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0XFF, 0xFF
> > + };
> > +
> > + __m512i v_shuffle = _mm512_loadu_si512((void *) ip_shuffle_mask);
> > +
> > + /* This shuffle is required for key and mask to match the layout of the
> > + * ip6_hdr struct. */
> > + __m512i v_key_shuf = _mm512_permutexvar_epi8(v_shuffle, v_key);
> > + __m512i v_mask_shuf = _mm512_permutexvar_epi8(v_shuffle,
> v_mask);
> > +
> > + /* Set the v_zero register to all zero's. */
> > + const __m128i v_zeros = _mm_setzero_si128();
> > +
> > + /* Set the v_all_ones register to all one's. */
> > + const __m128i v_all_ones = _mm_cmpeq_epi16(v_zeros, v_zeros);
> > +
> > + /* Load ip6 src and dst masks respectively into 128-bit wide
> > registers. */
> > + __m128i v_src = _mm_loadu_si128((void *) &mask->ipv6_src);
> > + __m128i v_dst = _mm_loadu_si128((void *) &mask->ipv6_dst);
> > +
> > + /* Perform a bitwise OR between src and dst registers. */
> > + __m128i v_or = _mm_or_si128(v_src, v_dst);
> > +
> > + /* Will return true if any bit has been set in v_or, else it will
> > return
> > + * false. */
> > + bool do_checksum = !_mm_test_all_zeros(v_or, v_all_ones);
> > +
> > + DP_PACKET_BATCH_FOR_EACH (i, packet, batch) {
> > + struct ovs_16aligned_ip6_hdr *nh = dp_packet_l3(packet);
> > +
> > + /* Load the 40 bytes of the IPv6 header. */
> > + __m512i v_packet = _mm512_maskz_loadu_epi64(0x1F, (void *)
> > + nh);
> > +
> > + /* AND the v_pkt_mask to the packet data (v_packet). */
> > + __m512i v_pkt_masked = _mm512_andnot_si512(v_mask_shuf,
> > + v_packet);
> > +
> > + /* OR the new addresses (v_key_shuf) with the masked packet
> addresses
> > + * (v_pkt_masked). */
> > + __m512i v_new_hdr = _mm512_or_si512(v_key_shuf,
> > + v_pkt_masked);
> > +
> > + /* If ip6_src or ip6_dst has been modified, L4 checksum needs to
> > + * be updated. */
> > + if (do_checksum) {
> > + uint8_t proto = nh->ip6_nxt;
> > + uint16_t delta_checksum =
> avx512_ipv6_addr_csum_delta(v_packet,
> > +
> > + v_new_hdr);
> > +
> > + if (proto == IPPROTO_UDP) {
> > + struct udp_header *uh = dp_packet_l4(packet);
> > +
> > + if (uh->udp_csum) {
> > + uint16_t old_udp_checksum = ~uh->udp_csum;
> > + uint32_t udp_checksum = old_udp_checksum +
> > + delta_checksum;
> > +
> > + udp_checksum = csum_finish(udp_checksum);
> > +
> > + if (!udp_checksum) {
> > + udp_checksum = htons(0xffff);
> > + }
> > +
> > + uh->udp_csum = udp_checksum;
> > + }
> > + } else if (proto == IPPROTO_TCP) {
> > + struct tcp_header *th = dp_packet_l4(packet);
> > + uint16_t old_tcp_checksum = ~th->tcp_csum;
> > + uint32_t tcp_checksum = old_tcp_checksum +
> > + delta_checksum;
> > +
> > + tcp_checksum = csum_finish(tcp_checksum);
> > + th->tcp_csum = tcp_checksum;
> > + } else if (proto == IPPROTO_ICMPV6) {
> > + struct icmp6_header *icmp = dp_packet_l4(packet);
> > + uint16_t old_icmp6_checksum = ~icmp->icmp6_cksum;
> > + uint32_t icmp6_checksum = old_icmp6_checksum +
> > + delta_checksum;
> > +
> > + icmp6_checksum = csum_finish(icmp6_checksum);
> > + icmp->icmp6_cksum = icmp6_checksum;
> > + }
> > + }
> > + /* Write back the modified IPv6 addresses. */
> > + _mm512_mask_storeu_epi64((void *) nh, 0x1F, v_new_hdr);
>
> Overindented.
>
Sure, will fix this.
> > + }
> > +}
> > +#endif /* HAVE_AVX512VBMI */
> > +
> > static void
> > action_avx512_set_masked(struct dp_packet_batch *batch, const struct
> > nlattr *a) { @@ -514,6 +711,13 @@ action_avx512_init(struct
> > odp_execute_action_impl *self OVS_UNUSED)
> > impl_set_masked_funcs[OVS_KEY_ATTR_ETHERNET] =
> action_avx512_eth_set_addrs;
> > impl_set_masked_funcs[OVS_KEY_ATTR_IPV4] =
> > action_avx512_ipv4_set_addrs;
> >
> > +#if HAVE_AVX512VBMI
> > + if (action_avx512vbmi_isa_probe()) {
> > + impl_set_masked_funcs[OVS_KEY_ATTR_IPV6] =
> > + action_avx512_ipv6_set_addrs;
> > + }
> > +#endif
> > +
> > return 0;
> > }
> >
> > diff --git a/lib/odp-execute-private.c b/lib/odp-execute-private.c
> > index f80ae5a23..8b86b1e4f 100644
> > --- a/lib/odp-execute-private.c
> > +++ b/lib/odp-execute-private.c
> > @@ -60,6 +60,23 @@ action_avx512_isa_probe(void)
> >
> > #endif
> >
> > +#if ACTION_IMPL_AVX512_CHECK && HAVE_AVX512VBMI bool
> > +action_avx512vbmi_isa_probe(void)
> > +{
> > + if (cpu_has_isa(OVS_CPU_ISA_X86_AVX512VBMI)) {
> > + return true;
> > + }
> > + return false;
>
> Hmm, should this be just:
> return cpu_has_isa(OVS_CPU_ISA_X86_AVX512VBMI);
> ?
Eelco, if you're okay with this change (as you asked for this function to be
changed in v4)?
I can update to the above.
<SNIP>
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