From: zhangfei <zhangfei.gao@linaro.org> To: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Arnd Bergmann <arnd@arndb.de>, Herbert Xu <herbert@gondor.apana.org.au>, jonathan.cameron@huawei.com, dave.jiang@intel.com, grant.likely@arm.com, jean-philippe <jean-philippe@linaro.org>, Jerome Glisse <jglisse@redhat.com>, ilias.apalodimas@linaro.org, francois.ozog@linaro.org, kenneth-lee-2012@foxmail.com, Wangzhou <wangzhou1@hisilicon.com>, "haojian . zhuang" <haojian.zhuang@linaro.org>, guodong.xu@linaro.org, linux-accelerators@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, iommu@lists.linux-foundation.org, Kenneth Lee <liguozhu@hisilicon.com>, Zaibo Xu <xuzaibo@huawei.com> Subject: Re: [PATCH v11 2/4] uacce: add uacce driver Date: Mon, 13 Jan 2020 11:34:55 +0800 [thread overview] Message-ID: <053ccd05-4f11-5be6-47c2-eee5c2f1fdc4@linaro.org> (raw) In-Reply-To: <20200111194006.GD435222@kroah.com> Hi, Greg Thanks for the review. On 2020/1/12 上午3:40, Greg Kroah-Hartman wrote: > On Sat, Jan 11, 2020 at 10:48:37AM +0800, Zhangfei Gao wrote: >> +static int uacce_fops_open(struct inode *inode, struct file *filep) >> +{ >> + struct uacce_mm *uacce_mm = NULL; >> + struct uacce_device *uacce; >> + struct uacce_queue *q; >> + int ret = 0; >> + >> + uacce = xa_load(&uacce_xa, iminor(inode)); >> + if (!uacce) >> + return -ENODEV; >> + >> + if (!try_module_get(uacce->parent->driver->owner)) >> + return -ENODEV; > Why are you trying to grab the module reference of the parent device? > Why is that needed and what is that going to help with here? > > This shouldn't be needed as the module reference of the owner of the > fileops for this module is incremented, and the "parent" module depends > on this module, so how could it be unloaded without this code being > unloaded? > > Yes, if you build this code into the kernel and the "parent" driver is a > module, then you will not have a reference, but when you remove that > parent driver the device will be removed as it has to be unregistered > before that parent driver can be removed from the system, right? > > Or what am I missing here? The refcount here is preventing rmmod "parent" module after fd is opened, since user driver has mmap kernel memory to user space, like mmio, which may still in-use. With the refcount protection, rmmod "parent" module will fail until application free the fd. log like: rmmod: ERROR: Module hisi_zip is in use > >> +static void uacce_release(struct device *dev) >> +{ >> + struct uacce_device *uacce = to_uacce_device(dev); >> + >> + kfree(uacce); >> + uacce = NULL; > That line didn't do anything :) Yes, this is a mistake. It is up to caller to set to NULL to prevent release multi times. Thanks
WARNING: multiple messages have this Message-ID (diff)
From: zhangfei <zhangfei.gao@linaro.org> To: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: jean-philippe <jean-philippe@linaro.org>, dave.jiang@intel.com, Herbert Xu <herbert@gondor.apana.org.au>, Arnd Bergmann <arnd@arndb.de>, francois.ozog@linaro.org, linux-accelerators@lists.ozlabs.org, ilias.apalodimas@linaro.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Jerome Glisse <jglisse@redhat.com>, grant.likely@arm.com, "haojian . zhuang" <haojian.zhuang@linaro.org>, linux-crypto@vger.kernel.org, Kenneth Lee <liguozhu@hisilicon.com>, guodong.xu@linaro.org, kenneth-lee-2012@foxmail.com Subject: Re: [PATCH v11 2/4] uacce: add uacce driver Date: Mon, 13 Jan 2020 11:34:55 +0800 [thread overview] Message-ID: <053ccd05-4f11-5be6-47c2-eee5c2f1fdc4@linaro.org> (raw) In-Reply-To: <20200111194006.GD435222@kroah.com> Hi, Greg Thanks for the review. On 2020/1/12 上午3:40, Greg Kroah-Hartman wrote: > On Sat, Jan 11, 2020 at 10:48:37AM +0800, Zhangfei Gao wrote: >> +static int uacce_fops_open(struct inode *inode, struct file *filep) >> +{ >> + struct uacce_mm *uacce_mm = NULL; >> + struct uacce_device *uacce; >> + struct uacce_queue *q; >> + int ret = 0; >> + >> + uacce = xa_load(&uacce_xa, iminor(inode)); >> + if (!uacce) >> + return -ENODEV; >> + >> + if (!try_module_get(uacce->parent->driver->owner)) >> + return -ENODEV; > Why are you trying to grab the module reference of the parent device? > Why is that needed and what is that going to help with here? > > This shouldn't be needed as the module reference of the owner of the > fileops for this module is incremented, and the "parent" module depends > on this module, so how could it be unloaded without this code being > unloaded? > > Yes, if you build this code into the kernel and the "parent" driver is a > module, then you will not have a reference, but when you remove that > parent driver the device will be removed as it has to be unregistered > before that parent driver can be removed from the system, right? > > Or what am I missing here? The refcount here is preventing rmmod "parent" module after fd is opened, since user driver has mmap kernel memory to user space, like mmio, which may still in-use. With the refcount protection, rmmod "parent" module will fail until application free the fd. log like: rmmod: ERROR: Module hisi_zip is in use > >> +static void uacce_release(struct device *dev) >> +{ >> + struct uacce_device *uacce = to_uacce_device(dev); >> + >> + kfree(uacce); >> + uacce = NULL; > That line didn't do anything :) Yes, this is a mistake. It is up to caller to set to NULL to prevent release multi times. Thanks _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2020-01-13 3:35 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-11 2:48 [PATCH v11 0/4] Add uacce module for Accelerator Zhangfei Gao 2020-01-11 2:48 ` Zhangfei Gao 2020-01-11 2:48 ` [PATCH v11 1/4] uacce: Add documents for uacce Zhangfei Gao 2020-01-11 2:48 ` Zhangfei Gao 2020-01-11 2:48 ` [PATCH v11 2/4] uacce: add uacce driver Zhangfei Gao 2020-01-11 2:48 ` Zhangfei Gao 2020-01-11 19:40 ` Greg Kroah-Hartman 2020-01-11 19:40 ` Greg Kroah-Hartman 2020-01-13 3:34 ` zhangfei [this message] 2020-01-13 3:34 ` zhangfei 2020-01-14 14:59 ` Greg Kroah-Hartman 2020-01-14 14:59 ` Greg Kroah-Hartman 2020-01-15 11:18 ` zhangfei 2020-01-15 11:18 ` zhangfei 2020-01-15 12:02 ` Greg Kroah-Hartman 2020-01-15 12:02 ` Greg Kroah-Hartman 2020-01-15 14:11 ` zhangfei 2020-01-15 14:11 ` zhangfei 2020-01-15 16:43 ` Dave Jiang 2020-01-15 16:43 ` Dave Jiang 2020-01-16 2:11 ` zhangfei 2020-01-16 2:11 ` zhangfei 2020-01-11 2:48 ` [PATCH v11 3/4] crypto: hisilicon - Remove module_param uacce_mode Zhangfei Gao 2020-01-11 2:48 ` Zhangfei Gao 2020-01-11 2:48 ` [PATCH v11 4/4] crypto: hisilicon - register zip engine to uacce Zhangfei Gao 2020-01-11 2:48 ` Zhangfei Gao
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