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

["Yang, Xiao/杨 晓" <yangx.jy@fujitsu.com>]

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,
Cc Ira,

When using PMEM with DAX mode(devdax or fsdax), we cannot ensure that 
iova_to_vaddr() can cast a u64 pfn to a vaddr, right? so we have to 
replace page_address() with kmap_local_page().

Without Ira's PKS patch set, I didn't see any failure when accessing 
remote PMEM with devdax mode by RDMA based on RXE. I don't know why I 
cannot trigger any failure in the condition.

> 
>> +		/* 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

OK

Best Regards,
Xiao Yang

> 
> Jason