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RE: [PATCH for 8.0] igb: Save more Tx states


From: Sriram Yagnaraman
Subject: RE: [PATCH for 8.0] igb: Save more Tx states
Date: Fri, 17 Mar 2023 15:26:06 +0000

> -----Original Message-----
> From: Akihiko Odaki <akihiko.odaki@daynix.com>
> Sent: Friday, 17 March 2023 15:21
> To: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
> Cc: qemu-devel@nongnu.org; Jason Wang <jasowang@redhat.com>; Dmitry
> Fleytman <dmitry.fleytman@gmail.com>; quintela@redhat.com; Philippe
> Mathieu-Daudé <philmd@linaro.org>
> Subject: Re: [PATCH for 8.0] igb: Save more Tx states
> 
> On 2023/03/17 22:08, Sriram Yagnaraman wrote:
> >
> >
> >> -----Original Message-----
> >> From: Akihiko Odaki <akihiko.odaki@daynix.com>
> >> Sent: Friday, 17 March 2023 13:25
> >> Cc: qemu-devel@nongnu.org; Jason Wang <jasowang@redhat.com>;
> Dmitry
> >> Fleytman <dmitry.fleytman@gmail.com>; quintela@redhat.com; Philippe
> >> Mathieu-Daudé <philmd@linaro.org>; Sriram Yagnaraman
> >> <sriram.yagnaraman@est.tech>; Akihiko Odaki
> >> <akihiko.odaki@daynix.com>
> >> Subject: [PATCH for 8.0] igb: Save more Tx states
> >>
> >> The current implementation of igb uses only part of a advanced Tx
> >> context descriptor and first data descriptor because it misses some
> >> features and sniffs the trait of the packet instead of respecting the
> >> packet type specified in the descriptor. However, we will certainly
> >> need the entire Tx context descriptor when we update igb to respect
> >> these ignored fields. Save the entire context descriptor and first
> >> data descriptor except the buffer address to prepare for such a change.
> >>
> >> This also introduces the distinction of contexts with different
> >> indexes, which was not present in e1000e but in igb.
> >>
> >> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> >> ---
> >> Supersedes: <20230316155707.27007-1-akihiko.odaki@daynix.com>
> >>
> >>   hw/net/igb.c      | 25 ++++++++++++++++++-------
> >>   hw/net/igb_core.c | 36 +++++++++++++++++++-----------------
> >>   hw/net/igb_core.h |  8 +++-----
> >>   3 files changed, 40 insertions(+), 29 deletions(-)
> >>
> >> diff --git a/hw/net/igb.c b/hw/net/igb.c index c6d753df87..7c05896325
> >> 100644
> >> --- a/hw/net/igb.c
> >> +++ b/hw/net/igb.c
> >> @@ -502,16 +502,27 @@ static int igb_post_load(void *opaque, int
> >> version_id)
> >>       return igb_core_post_load(&s->core);  }
> >>
> >> -static const VMStateDescription igb_vmstate_tx = {
> >> -    .name = "igb-tx",
> >> +static const VMStateDescription igb_vmstate_tx_ctx = {
> >> +    .name = "igb-tx-ctx",
> >>       .version_id = 1,
> >>       .minimum_version_id = 1,
> >>       .fields = (VMStateField[]) {
> >> -        VMSTATE_UINT16(vlan, struct igb_tx),
> >> -        VMSTATE_UINT16(mss, struct igb_tx),
> >> -        VMSTATE_BOOL(tse, struct igb_tx),
> >> -        VMSTATE_BOOL(ixsm, struct igb_tx),
> >> -        VMSTATE_BOOL(txsm, struct igb_tx),
> >> +        VMSTATE_UINT32(vlan_macip_lens, struct
> e1000_adv_tx_context_desc),
> >> +        VMSTATE_UINT32(seqnum_seed, struct e1000_adv_tx_context_desc),
> >> +        VMSTATE_UINT32(type_tucmd_mlhl, struct
> >> e1000_adv_tx_context_desc),
> >> +        VMSTATE_UINT32(mss_l4len_idx, struct e1000_adv_tx_context_desc),
> >> +    }
> >> +};
> >> +
> >> +static const VMStateDescription igb_vmstate_tx = {
> >> +    .name = "igb-tx",
> >> +    .version_id = 2,
> >> +    .minimum_version_id = 2,
> >> +    .fields = (VMStateField[]) {
> >> +        VMSTATE_STRUCT_ARRAY(ctx, struct igb_tx, 2, 0, igb_vmstate_tx_ctx,
> >> +                             struct e1000_adv_tx_context_desc),
> >> +        VMSTATE_UINT32(first_cmd_type_len, struct igb_tx),
> >> +        VMSTATE_UINT32(first_olinfo_status, struct igb_tx),
> >>           VMSTATE_BOOL(first, struct igb_tx),
> >>           VMSTATE_BOOL(skip_cp, struct igb_tx),
> >>           VMSTATE_END_OF_LIST()
> >> diff --git a/hw/net/igb_core.c b/hw/net/igb_core.c index
> >> a7c7bfdc75..36027c2b54 100644
> >> --- a/hw/net/igb_core.c
> >> +++ b/hw/net/igb_core.c
> >> @@ -389,8 +389,10 @@ igb_rss_parse_packet(IGBCore *core, struct
> >> NetRxPkt *pkt, bool tx,  static bool  igb_setup_tx_offloads(IGBCore
> >> *core, struct igb_tx
> >> *tx)  {
> >> -    if (tx->tse) {
> >> -        if (!net_tx_pkt_build_vheader(tx->tx_pkt, true, true, tx->mss)) {
> >> +    if (tx->first_cmd_type_len & E1000_ADVTXD_DCMD_TSE) {
> >> +        uint32_t idx = (tx->first_olinfo_status >> 4) & 1;
> >
> > [...] More below
> >
> >> +        uint32_t mss = tx->ctx[idx].mss_l4len_idx >> 16;
> >> +        if (!net_tx_pkt_build_vheader(tx->tx_pkt, true, true, mss))
> >> + {
> >>               return false;
> >>           }
> >>
> >> @@ -399,13 +401,13 @@ igb_setup_tx_offloads(IGBCore *core, struct
> >> igb_tx
> >> *tx)
> >>           return true;
> >>       }
> >>
> >> -    if (tx->txsm) {
> >> +    if (tx->first_olinfo_status & E1000_ADVTXD_POTS_TXSM) {
> >>           if (!net_tx_pkt_build_vheader(tx->tx_pkt, false, true, 0)) {
> >>               return false;
> >>           }
> >>       }
> >>
> >> -    if (tx->ixsm) {
> >> +    if (tx->first_olinfo_status & E1000_ADVTXD_POTS_IXSM) {
> >>           net_tx_pkt_update_ip_hdr_checksum(tx->tx_pkt);
> >>       }
> >>
> >> @@ -527,7 +529,7 @@ igb_process_tx_desc(IGBCore *core,  {
> >>       struct e1000_adv_tx_context_desc *tx_ctx_desc;
> >>       uint32_t cmd_type_len;
> >> -    uint32_t olinfo_status;
> >> +    uint32_t idx;
> >>       uint64_t buffer_addr;
> >>       uint16_t length;
> >>
> >> @@ -538,20 +540,19 @@ igb_process_tx_desc(IGBCore *core,
> >>               E1000_ADVTXD_DTYP_DATA) {
> >>               /* advanced transmit data descriptor */
> >>               if (tx->first) {
> >> -                olinfo_status = le32_to_cpu(tx_desc->read.olinfo_status);
> >> -
> >> -                tx->tse = !!(cmd_type_len & E1000_ADVTXD_DCMD_TSE);
> >> -                tx->ixsm = !!(olinfo_status & E1000_ADVTXD_POTS_IXSM);
> >> -                tx->txsm = !!(olinfo_status & E1000_ADVTXD_POTS_TXSM);
> >> -
> >> +                tx->first_cmd_type_len = cmd_type_len;
> >> +                tx->first_olinfo_status =
> >> + le32_to_cpu(tx_desc->read.olinfo_status);
> >>                   tx->first = false;
> >>               }
> >>           } else if ((cmd_type_len & E1000_ADVTXD_DTYP_CTXT) ==
> >>                      E1000_ADVTXD_DTYP_CTXT) {
> >>               /* advanced transmit context descriptor */
> >>               tx_ctx_desc = (struct e1000_adv_tx_context_desc *)tx_desc;
> >> -            tx->vlan = le32_to_cpu(tx_ctx_desc->vlan_macip_lens) >> 16;
> >> -            tx->mss = le32_to_cpu(tx_ctx_desc->mss_l4len_idx) >> 16;
> >> +            idx = (tx_ctx_desc->mss_l4len_idx >> 4) & 1;
> >
> > I do not know if there are any other drivers that use more than 2 contexts,
> but as I read 7.2.2.2.11 IDX (3), IDX is a 3 bit field.
> > The above line will interpret 3, 5 and 7 as 1 for e.g.
> 
> 7.2.1.4 "Transmit Contexts" says:
>  > The 82576 supports 32 context register sets on-chip (two per queue)
> 
> DPDK also uses only two contexts while its design is extensible and can use
> more if the hardware allows. Therefore, it can be concluded that the device
> actually has only two contexts.
> 
> I don't know why IDX is defined as 3-bit field, but I think it's safe to 
> ignore the
> other two bits as we do for the other reserved bits.

7.2.1.4 also clearly specifies that "The IDX field contains an index to one of 
the two queue contexts".
Thanks for replying to my comments.

> 
> >
> >> +            tx->ctx[idx].vlan_macip_lens = le32_to_cpu(tx_ctx_desc-
> >>> vlan_macip_lens);
> >> +            tx->ctx[idx].seqnum_seed = le32_to_cpu(tx_ctx_desc-
> >seqnum_seed);
> >> +            tx->ctx[idx].type_tucmd_mlhl = le32_to_cpu(tx_ctx_desc-
> >>> type_tucmd_mlhl);
> >> +            tx->ctx[idx].mss_l4len_idx =
> >> + le32_to_cpu(tx_ctx_desc->mss_l4len_idx);
> >>               return;
> >>           } else {
> >>               /* unknown descriptor type */ @@ -575,8 +576,10 @@
> >> igb_process_tx_desc(IGBCore *core,
> >>       if (cmd_type_len & E1000_TXD_CMD_EOP) {
> >>           if (!tx->skip_cp && net_tx_pkt_parse(tx->tx_pkt)) {
> >>               if (cmd_type_len & E1000_TXD_CMD_VLE) {
> >> -                net_tx_pkt_setup_vlan_header_ex(tx->tx_pkt, tx->vlan,
> >> -                    core->mac[VET] & 0xffff);
> >> +                idx = (tx->first_olinfo_status >> 4) & 1;
> >> +                uint16_t vlan = tx->ctx[idx].vlan_macip_lens >> 16;
> >> +                uint16_t vet = core->mac[VET] & 0xffff;
> >> +                net_tx_pkt_setup_vlan_header_ex(tx->tx_pkt, vlan,
> >> + vet);
> >>               }
> >>               if (igb_tx_pkt_send(core, tx, queue_index)) {
> >>                   igb_on_tx_done_update_stats(core, tx->tx_pkt); @@
> >> -4024,8
> >> +4027,7 @@ static void igb_reset(IGBCore *core, bool sw)
> >>       for (i = 0; i < ARRAY_SIZE(core->tx); i++) {
> >>           tx = &core->tx[i];
> >>           net_tx_pkt_reset(tx->tx_pkt);
> >> -        tx->vlan = 0;
> >> -        tx->mss = 0;
> >> +        memset(&tx->ctx, 0, sizeof(tx->ctx));
> >>           tx->tse = false;
> >>           tx->ixsm = false;
> >>           tx->txsm = false;
> >> diff --git a/hw/net/igb_core.h b/hw/net/igb_core.h index
> >> 814c1e264b..8914e0b801 100644
> >> --- a/hw/net/igb_core.h
> >> +++ b/hw/net/igb_core.h
> >> @@ -72,11 +72,9 @@ struct IGBCore {
> >>       QEMUTimer *autoneg_timer;
> >>
> >>       struct igb_tx {
> >> -        uint16_t vlan;  /* VLAN Tag */
> >> -        uint16_t mss;   /* Maximum Segment Size */
> >> -        bool tse;       /* TCP/UDP Segmentation Enable */
> >> -        bool ixsm;      /* Insert IP Checksum */
> >> -        bool txsm;      /* Insert TCP/UDP Checksum */
> >> +        struct e1000_adv_tx_context_desc ctx[2];
> >> +        uint32_t first_cmd_type_len;
> >> +        uint32_t first_olinfo_status;
> >>
> >>           bool first;
> >>           bool skip_cp;
> >> --
> >> 2.39.2
> >

LGTM
Reviewed-by: Sriram Yagnaraman <sriram.yagnaraman@est.tech>

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