Re: [PATCH bpf-next 2/2] riscv, bpf: Fix incorrect runtime stats

From: "Björn Töpel" <bjorn@kernel.org>
To: Pu Lehui <pulehui@huawei.com>,
	Xu Kuohai <xukuohai@huaweicloud.com>,
	bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-riscv@lists.infradead.org
Cc: Ivan Babrou <ivan@cloudflare.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [PATCH bpf-next 2/2] riscv, bpf: Fix incorrect runtime stats
Date: Tue, 16 Apr 2024 16:09:03 +0200	[thread overview]
Message-ID: <871q754cxs.fsf@all.your.base.are.belong.to.us> (raw)
In-Reply-To: <39b55f13-69a1-401e-b87e-1040e33c9368@huawei.com>

Pu Lehui <pulehui@huawei.com> writes:

> On 2024/4/16 14:42, Xu Kuohai wrote:
>> From: Xu Kuohai <xukuohai@huawei.com>
>> 
>> When __bpf_prog_enter() returns zero, the s1 register is not set to zero,
>> resulting in incorrect runtime stats. Fix it by setting s1 immediately upon
>> the return of __bpf_prog_enter().
>> 
>> Fixes: 49b5e77ae3e2 ("riscv, bpf: Add bpf trampoline support for RV64")
>> Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
>> ---
>>   arch/riscv/net/bpf_jit_comp64.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>> 
>> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
>> index 15e482f2c657..e713704be837 100644
>> --- a/arch/riscv/net/bpf_jit_comp64.c
>> +++ b/arch/riscv/net/bpf_jit_comp64.c
>> @@ -730,6 +730,9 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of
>>   	if (ret)
>>   		return ret;
>>   
>> +	/* store prog start time */
>> +	emit_mv(RV_REG_S1, RV_REG_A0, ctx);
>> +
>>   	/* if (__bpf_prog_enter(prog) == 0)
>>   	 *	goto skip_exec_of_prog;
>>   	 */
>> @@ -737,9 +740,6 @@ static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of
>>   	/* nop reserved for conditional jump */
>>   	emit(rv_nop(), ctx);
>>   
>> -	/* store prog start time */
>> -	emit_mv(RV_REG_S1, RV_REG_A0, ctx);
>> -
>>   	/* arg1: &args_off */
>>   	emit_addi(RV_REG_A0, RV_REG_FP, -args_off, ctx);
>>   	if (!p->jited)
>
> Thanks.
>
> Reviewed-by: Pu Lehui <pulehui@huawei.com>

Acked-by: Björn Töpel <bjorn@kernel.org>