Re: [RESEND PATCH v5 1/2] RDMA/rxe: Support RDMA Atomic Write operation

Yang, Xiao/杨 晓
2022-10-06T07:53:55Z

On 2022/9/24 6:22, Jason Gunthorpe wrote:
> On Fri, Jul 08, 2022 at 04:02:36AM +0000, yangx.jy@fujitsu.com wrote:
>> +static enum resp_states atomic_write_reply(struct rxe_qp *qp,
>> + struct rxe_pkt_info *pkt)
>> +{
>> + u64 src, *dst;
>> + struct resp_res *res = qp->resp.res;
>> + struct rxe_mr *mr = qp->resp.mr;
>> + int payload = payload_size(pkt);
>> +
>> + if (!res) {
>> + res = rxe_prepare_res(qp, pkt, RXE_ATOMIC_WRITE_MASK);
>> + qp->resp.res = res;
>> + }
>> +
>> + if (!res->replay) {
>> +#ifdef CONFIG_64BIT
>> + memcpy(&src, payload_addr(pkt), payload);
>> +
>> + dst = iova_to_vaddr(mr, qp->resp.va + qp->resp.offset, payload);
>> + /* check vaddr is 8 bytes aligned. */
>> + if (!dst || (uintptr_t)dst & 7)
>> + return RESPST_ERR_MISALIGNED_ATOMIC;
>> +
>> + /* Do atomic write after all prior operations have completed */
>> + smp_store_release(dst, src);
>
> Someone needs to fix iova_to_vaddr to do the missing kmap, we can't
> just assume you can cast a u64 pfn to a vaddr like this.

Hi Jason,

Sorry, it is still not clear to me after looking into the related code
again.

IMO, SoftRoCE depends on INFINIBAND_VIRT_DMA Kconfig which only allows
!HIGHMEM so that SoftRoCE can call page_address() to gain a kernel
virtual address for a page allocated on low memory zone. If a page is
allocated on high memory zone, we need to gain a kernel virtual address
by kmap()/kmap_atomic(). Did I miss something? I wonder why it is
necessary to call kmap()?

Reference:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b1e678bf290db5a76f1b6a9f7c381310e03440d6

Best Regards,
Xiao Yang

>
>> + /* decrease resp.resid to zero */
>> + qp->resp.resid -= sizeof(payload);
>> +
>> + qp->resp.msn++;
>> +
>> + /* next expected psn, read handles this separately */
>> + qp->resp.psn = (pkt->psn + 1) & BTH_PSN_MASK;
>> + qp->resp.ack_psn = qp->resp.psn;
>> +
>> + qp->resp.opcode = pkt->opcode;
>> + qp->resp.status = IB_WC_SUCCESS;
>> +
>> + return RESPST_ACKNOWLEDGE;
>> +#else
>> + pr_err("32-bit arch doesn't support 8-byte atomic write\n");
>> + return RESPST_ERR_UNSUPPORTED_OPCODE;
>
> No print on receiving a remote packet
>
> Jason