From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f51.google.com (mail-ej1-f51.google.com [209.85.218.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 521761F09A8 for ; Thu, 7 Aug 2025 08:34:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754555697; cv=none; b=IZTjUIeKvCB6yE31GPxpjHsP0QBp10gf2ONcJ4I5+zh3rLYUfvy/cd08d6HXsXmQ7KI5Sn/6vmH866hElyr8JMq+D0Oo1hJDA4eI+AULB9CCKEcDneNQp9MrbsMuzLUsIPpq5s/mb7qlkK1qLBz3BhOBpSjzx1jTbgCx6KLek08= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754555697; c=relaxed/simple; bh=uWhVeVke7mp28LVw7O2Q08aNSn1p+JkEi1AW6TCBYlg=; h=From:Date:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=U0asCOtEjK9QfDCmPRDlZ4sYpDlINGKt/XvsAE9AAbkAcbKNUtIri4IJMPi7e775YApIfLeHaGLAm7wxOZlVF1dVmiC3Df1txoTtV+SVcRCmneQIWxGvRcJ6gwRYI61jN1ZSDcDiw6+7n6nkXE5YSgKsjKoXGN2CTbFdUb9fiYM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Gy6gI8XJ; arc=none smtp.client-ip=209.85.218.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Gy6gI8XJ" Received: by mail-ej1-f51.google.com with SMTP id a640c23a62f3a-af93150f7c2so109460266b.3 for ; Thu, 07 Aug 2025 01:34:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1754555693; x=1755160493; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=1PuNyaJBvVgn+Zo+4qQQ4pr1y7L8DXjhSM01pJ0T4TY=; b=Gy6gI8XJEXSZ4AmqKWnddpY6aDbzkYC5uaBykVYflW9SwAFBAf8rkJYZy9fgGkvgMo aVO+navmmOIjYb2PbN76WEHUGYF4s6lJRdEtygaXEae03xm41bzhwAIekpgj7nVQx4bX mQD25DliZ0bLcu9LbfjmA2P3RnzVO0Hf1ixDZZNZ7tfo3ASoioX6D5/8W8r25HZCSw8J 8r3mc79chvKPBcwbx3hyOdX6aK08Gh9Dtb2zsAvSWcFHAUhGbeet58QwOOtvdMKZBarm ay5ueeEj2oYhPXUiOqoMLW46iILG+aun6mpzYeqrrg9s53Zt6bZjygGnMIdUc7ESzd3C Tweg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754555693; x=1755160493; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=1PuNyaJBvVgn+Zo+4qQQ4pr1y7L8DXjhSM01pJ0T4TY=; b=hCbIBTY0/Bmf93M6Wfr1DWdqF+vaL9sjcARtAPQV9zInIIJaEUN8XofMRgvAIiVB7p 5XQDSiw9KoLlQfx6PjgopN4HadqR0m17+/yUA1YlXChG9uuJO8F70fsZ3eZ+zAF092GW CRlNjkQAHdLiBIGZ4M1VloFKpTyqLpLypZGH4D2yC67k1y2qFtMmtuG8jJhm//jo2CO2 5pyFRWxByKgPfCt1QV61jqziPrctDDONkUB2vtY85LkTmdqVh8w3JrxQT2cM/7KoS6Ns HEXCPot/MsJ5xZft727nowvGcOyMKQjNEI1Og/gNqI2K3xlwKScLpKIKB984aicNn2hm yyNg== X-Gm-Message-State: AOJu0YxDaSTkK5w8buXYDALljYiHIZX5zkvQsn6c2NZjxrbM4vaDU+mu jaOmuVNosOPCsmKfRMNk77e+g/vRIq96lLUACh9/vh7WprGUq8oIVgWx X-Gm-Gg: ASbGncsgUmvxAEBdphZwd19zWxN5H32JrMQllCSwmiSxxV+YWkUSRw2swgwjV5bNgNM UGF3RuuWmh6BOoa7VMXkMwgH7WUc/swfSzGHrnFvw0cCD8ZaS1LcrdfLURkptIVHkqnkvcwCoJL 7upbOUL+LS0kXlmKwTMwTsIV7wvE6xwj3+k4LC85l16f7BZfo0giz0ghO379osgbApRNmpNwa+I QP1L7o5P13emXny+oyCsqOFCuoLCN2Xw/UnBn17KEUBHVq8fFti5teEpMpwkNDSRd+4yW3iptBf OgirFhFASL3Z7ozOCClQ6sS65+9Utd5T7c/jf2EHZ9t8i3r4dvnP1lEpFG22g5yAlR4UD0fA4sx LzVYLhHkR X-Google-Smtp-Source: AGHT+IGYmIxni7J3HYI1/dzRR+DY/8OvEX/XsNssTFs1nIOCP+lW0HgPQ9wHIykHWaIMtETv2lfoCQ== X-Received: by 2002:a17:907:94d6:b0:af2:5229:bd74 with SMTP id a640c23a62f3a-af990344c44mr486719866b.26.1754555693205; Thu, 07 Aug 2025 01:34:53 -0700 (PDT) Received: from krava ([173.38.220.55]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-af9383590desm1050023866b.76.2025.08.07.01.34.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Aug 2025 01:34:52 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Thu, 7 Aug 2025 10:34:50 +0200 To: Leon Hwang Cc: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, yonghong.song@linux.dev, song@kernel.org, eddyz87@gmail.com, dxu@dxuuu.xyz, deso@posteo.net, kernel-patches-bot@fb.com Subject: Re: [PATCH bpf-next v2 1/3] bpf: Introduce BPF_F_CPU flag for percpu_array maps Message-ID: References: <20250805163017.17015-1-leon.hwang@linux.dev> <20250805163017.17015-2-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250805163017.17015-2-leon.hwang@linux.dev> On Wed, Aug 06, 2025 at 12:30:15AM +0800, Leon Hwang wrote: > Introduce support for the BPF_F_CPU flag in percpu_array maps to allow > updating values for specified CPU or for all CPUs with a single value. > > This enhancement enables: > > * Efficient update of all CPUs using a single value when cpu == (u32)~0. > * Targeted update or lookup for a specified CPU otherwise. > > The flag is passed via: > > * map_flags in bpf_percpu_array_update() along with embedded cpu field. > * elem_flags in generic_map_update_batch() along with embedded cpu field. > > Signed-off-by: Leon Hwang > --- > include/linux/bpf.h | 3 +- > include/uapi/linux/bpf.h | 6 +++ > kernel/bpf/arraymap.c | 54 ++++++++++++++++++------ > kernel/bpf/syscall.c | 77 +++++++++++++++++++++------------- > tools/include/uapi/linux/bpf.h | 6 +++ > 5 files changed, 103 insertions(+), 43 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index cc700925b802f..c17c45f797ed9 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -2691,7 +2691,8 @@ int map_set_for_each_callback_args(struct bpf_verifier_env *env, > struct bpf_func_state *callee); > > int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value); > -int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value); > +int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value, > + u64 flags); > int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value, > u64 flags); > int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value, > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 233de8677382e..67bc35e4d6a8d 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -1372,6 +1372,12 @@ enum { > BPF_NOEXIST = 1, /* create new element if it didn't exist */ > BPF_EXIST = 2, /* update existing element */ > BPF_F_LOCK = 4, /* spin_lock-ed map_lookup/map_update */ > + BPF_F_CPU = 8, /* map_update for percpu_array */ > +}; > + > +enum { > + /* indicate updating value across all CPUs for percpu maps. */ > + BPF_ALL_CPUS = (__u32)~0, > }; > > /* flags for BPF_MAP_CREATE command */ > diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c > index 3d080916faf97..98759f0b22397 100644 > --- a/kernel/bpf/arraymap.c > +++ b/kernel/bpf/arraymap.c > @@ -295,17 +295,24 @@ static void *percpu_array_map_lookup_percpu_elem(struct bpf_map *map, void *key, > return per_cpu_ptr(array->pptrs[index & array->index_mask], cpu); > } > > -int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value) > +int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value, u64 flags) > { > struct bpf_array *array = container_of(map, struct bpf_array, map); > u32 index = *(u32 *)key; > void __percpu *pptr; > - int cpu, off = 0; > - u32 size; > + u32 size, cpu; > + int off = 0; > > if (unlikely(index >= array->map.max_entries)) > return -ENOENT; > > + cpu = flags >> 32; > + flags &= (u32)~0; is this necessary? > + if (unlikely(flags > BPF_F_CPU)) > + return -EINVAL; > + if (unlikely((flags & BPF_F_CPU) && cpu >= num_possible_cpus())) > + return -ERANGE; should we check cpu != BPF_ALL_CPUS in here? > + > /* per_cpu areas are zero-filled and bpf programs can only > * access 'value_size' of them, so copying rounded areas > * will not leak any kernel data > @@ -313,10 +320,15 @@ int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value) > size = array->elem_size; > rcu_read_lock(); > pptr = array->pptrs[index & array->index_mask]; > - for_each_possible_cpu(cpu) { > - copy_map_value_long(map, value + off, per_cpu_ptr(pptr, cpu)); > - check_and_init_map_value(map, value + off); > - off += size; > + if (flags & BPF_F_CPU) { > + copy_map_value_long(map, value, per_cpu_ptr(pptr, cpu)); > + check_and_init_map_value(map, value); > + } else { > + for_each_possible_cpu(cpu) { > + copy_map_value_long(map, value + off, per_cpu_ptr(pptr, cpu)); > + check_and_init_map_value(map, value + off); > + off += size; > + } > } > rcu_read_unlock(); > return 0; > @@ -387,13 +399,20 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value, > struct bpf_array *array = container_of(map, struct bpf_array, map); > u32 index = *(u32 *)key; > void __percpu *pptr; > - int cpu, off = 0; > - u32 size; > + u32 size, cpu; > + int off = 0; > > - if (unlikely(map_flags > BPF_EXIST)) > + cpu = map_flags >> 32; > + map_flags &= (u32)~0; > + if (unlikely(map_flags > BPF_F_CPU)) > /* unknown flags */ > return -EINVAL; > > + if (unlikely((map_flags & BPF_F_CPU) && cpu != BPF_ALL_CPUS && > + cpu >= num_possible_cpus())) > + /* invalid cpu */ > + return -ERANGE; looks like same check as in bpf_percpu_array_copy, maybe we could add some helper function for that? > + > if (unlikely(index >= array->map.max_entries)) > /* all elements were pre-allocated, cannot insert a new one */ > return -E2BIG; > @@ -411,10 +430,19 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value, > size = array->elem_size; > rcu_read_lock(); > pptr = array->pptrs[index & array->index_mask]; > - for_each_possible_cpu(cpu) { > - copy_map_value_long(map, per_cpu_ptr(pptr, cpu), value + off); > + if ((map_flags & BPF_F_CPU) && cpu != BPF_ALL_CPUS) { > + copy_map_value_long(map, per_cpu_ptr(pptr, cpu), value); > bpf_obj_free_fields(array->map.record, per_cpu_ptr(pptr, cpu)); > - off += size; > + } else { > + for_each_possible_cpu(cpu) { > + copy_map_value_long(map, per_cpu_ptr(pptr, cpu), value + off); > + /* same user-provided value is used if BPF_F_CPU is specified, > + * otherwise value is an array of per-cpu values. > + */ > + if (!(map_flags & BPF_F_CPU)) > + off += size; > + bpf_obj_free_fields(array->map.record, per_cpu_ptr(pptr, cpu)); > + } > } > rcu_read_unlock(); > return 0; > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 0fbfa8532c392..43f19d02bc5ce 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -131,8 +131,11 @@ bool bpf_map_write_active(const struct bpf_map *map) > return atomic64_read(&map->writecnt) != 0; > } > > -static u32 bpf_map_value_size(const struct bpf_map *map) > +static u32 bpf_map_value_size(const struct bpf_map *map, u64 flags) > { > + if ((flags & BPF_F_CPU) && map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) > + return round_up(map->value_size, 8); > + nit, maybe we could keep the same style like below and check the map type first: if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY && (flags & BPF_F_CPU)) return round_up(map->value_size, 8); else if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH || > map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH || > map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY || > @@ -314,7 +317,7 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value, > map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) { > err = bpf_percpu_hash_copy(map, key, value); > } else if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) { > - err = bpf_percpu_array_copy(map, key, value); > + err = bpf_percpu_array_copy(map, key, value, flags); > } else if (map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE) { > err = bpf_percpu_cgroup_storage_copy(map, key, value); > } else if (map->map_type == BPF_MAP_TYPE_STACK_TRACE) { > @@ -1669,7 +1672,10 @@ static int map_lookup_elem(union bpf_attr *attr) > if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM)) > return -EINVAL; > > - if (attr->flags & ~BPF_F_LOCK) > + if ((u32)attr->flags & ~(BPF_F_LOCK | BPF_F_CPU)) > + return -EINVAL; I understand the u32 cast in here.. > + > + if (!((u32)attr->flags & BPF_F_CPU) && attr->flags >> 32) > return -EINVAL; .. but do we need it in here and other similar places below? > > CLASS(fd, f)(attr->map_fd); > @@ -1679,7 +1685,7 @@ static int map_lookup_elem(union bpf_attr *attr) > if (!(map_get_sys_perms(map, f) & FMODE_CAN_READ)) > return -EPERM; > > - if ((attr->flags & BPF_F_LOCK) && > + if (((u32)attr->flags & BPF_F_LOCK) && > !btf_record_has_field(map->record, BPF_SPIN_LOCK)) > return -EINVAL; > > @@ -1687,7 +1693,7 @@ static int map_lookup_elem(union bpf_attr *attr) > if (IS_ERR(key)) > return PTR_ERR(key); > > - value_size = bpf_map_value_size(map); > + value_size = bpf_map_value_size(map, attr->flags); > > err = -ENOMEM; > value = kvmalloc(value_size, GFP_USER | __GFP_NOWARN); > @@ -1744,19 +1750,24 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr) > goto err_put; > } > > - if ((attr->flags & BPF_F_LOCK) && > + if (((u32)attr->flags & BPF_F_LOCK) && > !btf_record_has_field(map->record, BPF_SPIN_LOCK)) { > err = -EINVAL; > goto err_put; > } > > + if (!((u32)attr->flags & BPF_F_CPU) && attr->flags >> 32) { > + err = -EINVAL; > + goto err_put; > + } > + > key = ___bpf_copy_key(ukey, map->key_size); > if (IS_ERR(key)) { > err = PTR_ERR(key); > goto err_put; > } > > - value_size = bpf_map_value_size(map); > + value_size = bpf_map_value_size(map, attr->flags); > value = kvmemdup_bpfptr(uvalue, value_size); > if (IS_ERR(value)) { > err = PTR_ERR(value); > @@ -1942,6 +1953,25 @@ int generic_map_delete_batch(struct bpf_map *map, > return err; > } > > +static int check_map_batch_elem_flags(struct bpf_map *map, u64 elem_flags) > +{ > + u32 flags = elem_flags; > + > + if (flags & ~(BPF_F_LOCK | BPF_F_CPU)) > + return -EINVAL; > + > + if ((flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK)) > + return -EINVAL; > + > + if (!(flags & BPF_F_CPU) && elem_flags >> 32) > + return -EINVAL; > + > + if ((flags & BPF_F_CPU) && map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY) > + return -EINVAL; > + > + return 0; > +} it seems like this check could be used also for non-batch functions as well? also it might be more readable if we factor some check_flags function in separate patch and then add BPF_F_CPU support > + > int generic_map_update_batch(struct bpf_map *map, struct file *map_file, > const union bpf_attr *attr, > union bpf_attr __user *uattr) > @@ -1952,15 +1982,11 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file, > void *key, *value; > int err = 0; > > - if (attr->batch.elem_flags & ~BPF_F_LOCK) > - return -EINVAL; > - > - if ((attr->batch.elem_flags & BPF_F_LOCK) && > - !btf_record_has_field(map->record, BPF_SPIN_LOCK)) { > - return -EINVAL; > - } > + err = check_map_batch_elem_flags(map, attr->batch.elem_flags); > + if (err) > + return err; > > - value_size = bpf_map_value_size(map); > + value_size = bpf_map_value_size(map, attr->batch.elem_flags); > > max_count = attr->batch.count; > if (!max_count) > @@ -1986,9 +2012,7 @@ int generic_map_update_batch(struct bpf_map *map, struct file *map_file, > copy_from_user(value, values + cp * value_size, value_size)) > break; > > - err = bpf_map_update_value(map, map_file, key, value, > - attr->batch.elem_flags); > - > + err = bpf_map_update_value(map, map_file, key, value, attr->batch.elem_flags); there's no change in here right? I'd keep it as it is > if (err) > break; > cond_resched(); > @@ -2015,14 +2039,11 @@ int generic_map_lookup_batch(struct bpf_map *map, > u32 value_size, cp, max_count; > int err; > > - if (attr->batch.elem_flags & ~BPF_F_LOCK) > - return -EINVAL; > - > - if ((attr->batch.elem_flags & BPF_F_LOCK) && > - !btf_record_has_field(map->record, BPF_SPIN_LOCK)) > - return -EINVAL; > + err = check_map_batch_elem_flags(map, attr->batch.elem_flags); > + if (err) > + return err; > > - value_size = bpf_map_value_size(map); > + value_size = bpf_map_value_size(map, attr->batch.elem_flags); > > max_count = attr->batch.count; > if (!max_count) > @@ -2056,9 +2077,7 @@ int generic_map_lookup_batch(struct bpf_map *map, > rcu_read_unlock(); > if (err) > break; > - err = bpf_map_copy_value(map, key, value, > - attr->batch.elem_flags); > - > + err = bpf_map_copy_value(map, key, value, attr->batch.elem_flags); ditto thanks, jirka > if (err == -ENOENT) > goto next_key; > > @@ -2144,7 +2163,7 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr) > goto err_put; > } > > - value_size = bpf_map_value_size(map); > + value_size = bpf_map_value_size(map, 0); > > err = -ENOMEM; > value = kvmalloc(value_size, GFP_USER | __GFP_NOWARN); > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h > index 233de8677382e..67bc35e4d6a8d 100644 > --- a/tools/include/uapi/linux/bpf.h > +++ b/tools/include/uapi/linux/bpf.h > @@ -1372,6 +1372,12 @@ enum { > BPF_NOEXIST = 1, /* create new element if it didn't exist */ > BPF_EXIST = 2, /* update existing element */ > BPF_F_LOCK = 4, /* spin_lock-ed map_lookup/map_update */ > + BPF_F_CPU = 8, /* map_update for percpu_array */ > +}; > + > +enum { > + /* indicate updating value across all CPUs for percpu maps. */ > + BPF_ALL_CPUS = (__u32)~0, > }; > > /* flags for BPF_MAP_CREATE command */ > -- > 2.50.1 > >