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Fri, 30 May 2025 02:30:13 -0700 (PDT) From: Bo Li To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, luto@kernel.org, kees@kernel.org, akpm@linux-foundation.org, david@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, peterz@infradead.org Cc: dietmar.eggemann@arm.com, hpa@zytor.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, jannh@google.com, pfalcato@suse.de, riel@surriel.com, harry.yoo@oracle.com, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, yinhongbo@bytedance.com, dengliang.1214@bytedance.com, xieyongji@bytedance.com, chaiwen.cc@bytedance.com, songmuchun@bytedance.com, yuanzhu@bytedance.com, chengguozhu@bytedance.com, sunjiadong.lff@bytedance.com, Bo Li Subject: [RFC v2 07/35] RPAL: enable shared page mmap Date: Fri, 30 May 2025 17:27:35 +0800 Message-Id: <11d4a94318efc8af41f77235f5117aabb8795afe.1748594840.git.libo.gcs85@bytedance.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" RPAL needs to create shared memory between the kernel and user space for the transfer of states and data. This patch implements the rpal_mmap() interface. User processes can create shared memory by calling mmap() on /proc/rpal. To prevent users from creating excessive memory, rpal_mmap() limits the total size of the shared memory that can be created. The shared memory is maintained through reference counting, and rpal_munmap() is implemented for the release of the shared memory. Signed-off-by: Bo Li --- arch/x86/rpal/internal.h | 20 ++++++ arch/x86/rpal/mm.c | 147 +++++++++++++++++++++++++++++++++++++++ arch/x86/rpal/proc.c | 1 + arch/x86/rpal/service.c | 4 ++ include/linux/rpal.h | 15 ++++ mm/mmap.c | 4 ++ 6 files changed, 191 insertions(+) diff --git a/arch/x86/rpal/internal.h b/arch/x86/rpal/internal.h index c102a4c50515..65fd14a26f0e 100644 --- a/arch/x86/rpal/internal.h +++ b/arch/x86/rpal/internal.h @@ -9,8 +9,28 @@ #define RPAL_COMPAT_VERSION 1 #define RPAL_API_VERSION 1 =20 +#include +#include + extern bool rpal_inited; =20 /* service.c */ int __init rpal_service_init(void); void __init rpal_service_exit(void); + +/* mm.c */ +static inline struct rpal_shared_page * +rpal_get_shared_page(struct rpal_shared_page *rsp) +{ + atomic_inc(&rsp->refcnt); + return rsp; +} + +static inline void rpal_put_shared_page(struct rpal_shared_page *rsp) +{ + atomic_dec(&rsp->refcnt); +} + +int rpal_mmap(struct file *filp, struct vm_area_struct *vma); +struct rpal_shared_page *rpal_find_shared_page(struct rpal_service *rs, + unsigned long addr); diff --git a/arch/x86/rpal/mm.c b/arch/x86/rpal/mm.c index f469bcf57b66..8a738c502d1d 100644 --- a/arch/x86/rpal/mm.c +++ b/arch/x86/rpal/mm.c @@ -11,6 +11,8 @@ #include #include =20 +#include "internal.h" + static inline int rpal_balloon_mapping(unsigned long base, unsigned long s= ize) { struct vm_area_struct *vma; @@ -68,3 +70,148 @@ int rpal_balloon_init(unsigned long base) =20 return ret; } + +static void rpal_munmap(struct vm_area_struct *area) +{ + struct mm_struct *mm =3D area->vm_mm; + struct rpal_service *rs =3D mm->rpal_rs; + struct rpal_shared_page *rsp =3D area->vm_private_data; + + if (!rs) { + rpal_err( + "free shared page after exit_mmap or fork a child process\n"); + return; + } + + mutex_lock(&rs->mutex); + if (unlikely(!atomic_dec_and_test(&rsp->refcnt))) { + rpal_err("refcnt(%d) of shared page is not 0\n", atomic_read(&rsp->refcn= t)); + send_sig_info(SIGKILL, SEND_SIG_PRIV, rs->group_leader); + } + + list_del(&rsp->list); + rs->nr_shared_pages -=3D rsp->npage; + __free_pages(virt_to_page(rsp->kernel_start), get_order(rsp->npage)); + kfree(rsp); + mutex_unlock(&rs->mutex); +} + +const struct vm_operations_struct rpal_vm_ops =3D { .close =3D rpal_munmap= }; + +#define RPAL_MAX_SHARED_PAGES 8192 + +int rpal_mmap(struct file *filp, struct vm_area_struct *vma) +{ + struct rpal_service *cur =3D rpal_current_service(); + struct rpal_shared_page *rsp; + struct page *page =3D NULL; + unsigned long size =3D (unsigned long)(vma->vm_end - vma->vm_start); + int npage; + int order =3D -1; + int ret =3D 0; + + if (!cur) { + ret =3D -EINVAL; + goto out; + } + + /* + * Check whether the vma is aligned and whether the page number + * is power of 2. This makes shared pages easy to manage. + */ + if (!IS_ALIGNED(size, PAGE_SIZE) || + !IS_ALIGNED(vma->vm_start, PAGE_SIZE)) { + ret =3D -EINVAL; + goto out; + } + + npage =3D size >> PAGE_SHIFT; + if (!is_power_of_2(npage)) { + ret =3D -EINVAL; + goto out; + } + + order =3D get_order(size); + + mutex_lock(&cur->mutex); + + /* make sure user does not alloc too much pages */ + if (cur->nr_shared_pages + npage > RPAL_MAX_SHARED_PAGES) { + ret =3D -ENOMEM; + goto unlock; + } + + rsp =3D kmalloc(sizeof(*rsp), GFP_KERNEL); + if (!rsp) { + ret =3D -EAGAIN; + goto unlock; + } + + page =3D alloc_pages(GFP_KERNEL | __GFP_ZERO, order); + if (!page) { + ret =3D -ENOMEM; + goto free_rsp; + } + + rsp->user_start =3D vma->vm_start; + rsp->kernel_start =3D (unsigned long)page_address(page); + rsp->npage =3D npage; + atomic_set(&rsp->refcnt, 1); + INIT_LIST_HEAD(&rsp->list); + list_add(&rsp->list, &cur->shared_pages); + + vma->vm_ops =3D &rpal_vm_ops; + vma->vm_private_data =3D rsp; + + /* map to shared pages userspace */ + ret =3D remap_pfn_range(vma, vma->vm_start, page_to_pfn(page), size, + vma->vm_page_prot); + if (ret) + goto free_page; + + cur->nr_shared_pages +=3D npage; + mutex_unlock(&cur->mutex); + + return 0; + +free_page: + __free_pages(page, order); + list_del(&rsp->list); +free_rsp: + kfree(rsp); +unlock: + mutex_unlock(&cur->mutex); +out: + return ret; +} + +struct rpal_shared_page *rpal_find_shared_page(struct rpal_service *rs, + unsigned long addr) +{ + struct rpal_service *cur =3D rpal_current_service(); + struct rpal_shared_page *rsp, *ret =3D NULL; + + mutex_lock(&cur->mutex); + list_for_each_entry(rsp, &rs->shared_pages, list) { + if (rsp->user_start <=3D addr && + addr < rsp->user_start + rsp->npage * PAGE_SIZE) { + ret =3D rpal_get_shared_page(rsp); + break; + } + } + mutex_unlock(&cur->mutex); + + return ret; +} + +void rpal_exit_mmap(struct mm_struct *mm) +{ + struct rpal_service *rs =3D mm->rpal_rs; + + if (rs) { + mm->rpal_rs =3D NULL; + /* all shared pages should be freed at this time */ + WARN_ON_ONCE(rs->nr_shared_pages !=3D 0); + rpal_put_service(rs); + } +} diff --git a/arch/x86/rpal/proc.c b/arch/x86/rpal/proc.c index 1ced30e25c15..86947dc233d0 100644 --- a/arch/x86/rpal/proc.c +++ b/arch/x86/rpal/proc.c @@ -61,6 +61,7 @@ static long rpal_ioctl(struct file *file, unsigned int cm= d, unsigned long arg) const struct proc_ops proc_rpal_operations =3D { .proc_open =3D rpal_open, .proc_ioctl =3D rpal_ioctl, + .proc_mmap =3D rpal_mmap, }; =20 static int __init proc_rpal_init(void) diff --git a/arch/x86/rpal/service.c b/arch/x86/rpal/service.c index caa4afa5a2c6..f29a046fc22f 100644 --- a/arch/x86/rpal/service.c +++ b/arch/x86/rpal/service.c @@ -173,6 +173,10 @@ struct rpal_service *rpal_register_service(void) if (unlikely(rs->key =3D=3D RPAL_INVALID_KEY)) goto key_fail; =20 + mutex_init(&rs->mutex); + rs->nr_shared_pages =3D 0; + INIT_LIST_HEAD(&rs->shared_pages); + rs->bad_service =3D false; rs->base =3D calculate_base_address(rs->id); =20 diff --git a/include/linux/rpal.h b/include/linux/rpal.h index 3bc2a2a44265..986dfbd16fc9 100644 --- a/include/linux/rpal.h +++ b/include/linux/rpal.h @@ -110,6 +110,12 @@ struct rpal_service { * Fields above should never change after initialization. * Fields below may change after initialization. */ + /* Mutex for time consuming operations */ + struct mutex mutex; + + /* pinned pages */ + int nr_shared_pages; + struct list_head shared_pages; =20 /* delayed service put work */ struct delayed_work delayed_put_work; @@ -135,6 +141,14 @@ struct rpal_version_info { =20 /* End */ =20 +struct rpal_shared_page { + unsigned long user_start; + unsigned long kernel_start; + int npage; + atomic_t refcnt; + struct list_head list; +}; + enum rpal_command_type { RPAL_CMD_GET_API_VERSION_AND_CAP, RPAL_CMD_GET_SERVICE_KEY, @@ -196,6 +210,7 @@ struct rpal_service *rpal_get_service_by_key(u64 key); void copy_rpal(struct task_struct *p); void exit_rpal(bool group_dead); int rpal_balloon_init(unsigned long base); +void rpal_exit_mmap(struct mm_struct *mm); =20 extern void rpal_pick_mmap_base(struct mm_struct *mm, struct rlimit *rlim_stack); diff --git a/mm/mmap.c b/mm/mmap.c index bd210aaf7ebd..98bb33d2091e 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -48,6 +48,7 @@ #include #include #include +#include =20 #include #include @@ -1319,6 +1320,9 @@ void exit_mmap(struct mm_struct *mm) __mt_destroy(&mm->mm_mt); mmap_write_unlock(mm); vm_unacct_memory(nr_accounted); +#if IS_ENABLED(CONFIG_RPAL) + rpal_exit_mmap(mm); +#endif } =20 /* Insert vm structure into process list sorted by address --=20 2.20.1