Merge: powerpc ibmveth rx buffer hcall support

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/7160

Description: powerpc ibmveth rx buffer hcall support

JIRA: https://issues.redhat.com/browse/RHEL-104667

Build Info: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=68537524

Tested: Verified Brew build test kernel RPMs

Signed-off-by: Mamatha Inamdar <minamdar@redhat.com>

commit 2094200
Author: Mingming Cao <mmc@linux.ibm.com>
Date:   Sat Jul 19 05:13:56 2025 -0400

    ibmveth: Add multi buffers rx replenishment hcall support

    This patch enables batched RX buffer replenishment in ibmveth by
    using the new firmware-supported h_add_logical_lan_buffers() hcall
     to submit up to 8 RX buffers in a single call, instead of repeatedly
    calling the single-buffer h_add_logical_lan_buffer() hcall.

    During the probe, with the patch, the driver queries ILLAN attributes
    to detect IBMVETH_ILLAN_RX_MULTI_BUFF_SUPPORT bit. If the attribute is
    present, rx_buffers_per_hcall is set to 8, enabling batched replenishment.
    Otherwise, it defaults to 1, preserving the original upstream behavior
     with no change in code flow for unsupported systems.

    The core rx replenish logic remains the same. But when batching
    is enabled, the driver aggregates up to 8 fully prepared descriptors
    into a single h_add_logical_lan_buffers() hypercall. If any allocation
    or DMA mapping fails while preparing a batch, only the successfully
    prepared buffers are submitted, and the remaining are deferred for
    the next replenish cycle.

    If at runtime the firmware stops accepting the batched hcall—e,g,
    after a Live Partition Migration (LPM) to a host that does not
    support h_add_logical_lan_buffers(), the hypercall returns H_FUNCTION.
    In that case, the driver transparently disables batching, resets
    rx_buffers_per_hcall to 1, and falls back to the single-buffer hcall
    in next future replenishments to take care of these and future buffers.

    Test were done on systems with firmware that both supports and
    does not support the new h_add_logical_lan_buffers hcall.

    On supported firmware, this reduces hypercall overhead significantly
    over multiple buffers. SAR measurements showed about a 15% improvement
    in packet processing rate under moderate RX load, with heavier traffic
    seeing gains more than 30%

    Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
    Reviewed-by: Brian King <bjking1@linux.ibm.com>
    Reviewed-by: Haren Myneni <haren@linux.ibm.com>
    Reviewed-by: Dave Marquardt <davemarq@linux.ibm.com>
    Reviewed-by: Simon Horman <horms@kernel.org>
    Link: https://patch.msgid.link/20250719091356.57252-1-mmc@linux.ibm.com
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Signed-off-by: Mamatha Inamdar <minamdar@redhat.com>

Approved-by: Steve Best <sbest@redhat.com>
Approved-by: Michal Schmidt <mschmidt@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

arch/powerpc/include/asm/hvcall.h

@@ -258,6 +258,7 @@
 #define H_QUERY_INT_STATE       0x1E4
 #define H_POLL_PENDING		0x1D8
 #define H_ILLAN_ATTRIBUTES	0x244
+#define H_ADD_LOGICAL_LAN_BUFFERS 0x248
 #define H_MODIFY_HEA_QP		0x250
 #define H_QUERY_HEA_QP		0x254
 #define H_QUERY_HEA		0x258