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Tue, 3 Nov 2020 10:34:00 +0000 (UTC) Message-Id: <20201103095859.228149242@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1604399635; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=tAqolpusecj6Rd5JZ2LrxoX+tAqXPkBXuxrNCgE7FCw=; b=qh+T7IZJ6XcRj8DNIDr8HGAfo5YvTmXHwq7DmzffZLhC0V3WhpCRSbpdXm7hhOxtFFuwbX wcbVZVYetZLaKe7fxMMqkbtdTm/GbTXib0BTsgIk5kSnOSw9pXw7dXdWDZHGLuLfD8o7J5 iC45ybMzMZHPHXGAY6pKU82Xsx4uzeXlXRI1QCfZtr2oUImFGtEYcJEW2pZcbSXkaBhDfz vpMVSLl8t8kbeOeTl0nQMa9QXaNtYJbeM0FUqyI7W0BkGez+lZ161K3tVZxVFnDyF0wgMR 3UtPYUbq3j37JroTzUdlG8e/Z5n94SJYzJZktKJf9b+cElB2OmZliJy+9HhbJw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1604399635; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=tAqolpusecj6Rd5JZ2LrxoX+tAqXPkBXuxrNCgE7FCw=; b=r11Fcy33cu1nvwv6ClgNjFFAD2Uh7JIIgyfidherdoguvpBCo73VaZrmwbm0NX6rZ9Kudo xO58/+jD1GK3/sBA== Date: Tue, 03 Nov 2020 10:27:38 +0100 From: Thomas Gleixner To: LKML Cc: Linus Torvalds , Peter Zijlstra , Paul McKenney , Christoph Hellwig , Sebastian Andrzej Siewior , Andrew Morton , linux-mm@kvack.org, Alexander Viro , Benjamin LaHaise , linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, Chris Mason , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org, x86@kernel.org, Vineet Gupta , linux-snps-arc@lists.infradead.org, Russell King , Arnd Bergmann , linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, Michal Simek , Thomas Bogendoerfer , linux-mips@vger.kernel.org, Nick Hu , Greentime Hu , Vincent Chen , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, "David S. Miller" , sparclinux@vger.kernel.org, Chris Zankel , Max Filippov , linux-xtensa@linux-xtensa.org, Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Christian Koenig , Huang Rui , David Airlie , Daniel Vetter , dri-devel@lists.freedesktop.org, VMware Graphics , Roland Scheidegger , Dave Airlie , Gerd Hoffmann , virtualization@lists.linux-foundation.org, spice-devel@lists.freedesktop.org, Ben Skeggs , nouveau@lists.freedesktop.org, Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , intel-gfx@lists.freedesktop.org Subject: [patch V3 26/37] io-mapping: Provide iomap_local variant References: <20201103092712.714480842@linutronix.de> MIME-Version: 1.0 Content-transfer-encoding: 8-bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Similar to kmap local provide a iomap local variant which only disables migration, but neither disables pagefaults nor preemption. Signed-off-by: Thomas Gleixner --- V3: Restrict migrate disable to the 32bit mapping case and update documentation. V2: Split out from the large combo patch and add the !IOMAP_ATOMIC variants --- Documentation/driver-api/io-mapping.rst | 76 +++++++++++++++++++------------- include/linux/io-mapping.h | 30 +++++++++++- 2 files changed, 74 insertions(+), 32 deletions(-) --- a/Documentation/driver-api/io-mapping.rst +++ b/Documentation/driver-api/io-mapping.rst @@ -20,55 +20,71 @@ as it would consume too much of the kern mappable, while 'size' indicates how large a mapping region to enable. Both are in bytes. -This _wc variant provides a mapping which may only be used -with the io_mapping_map_atomic_wc or io_mapping_map_wc. +This _wc variant provides a mapping which may only be used with +io_mapping_map_atomic_wc(), io_mapping_map_local_wc() or +io_mapping_map_wc(). + +With this mapping object, individual pages can be mapped either temporarily +or long term, depending on the requirements. Of course, temporary maps are +more efficient. They come in two flavours:: -With this mapping object, individual pages can be mapped either atomically -or not, depending on the necessary scheduling environment. Of course, atomic -maps are more efficient:: + void *io_mapping_map_local_wc(struct io_mapping *mapping, + unsigned long offset) void *io_mapping_map_atomic_wc(struct io_mapping *mapping, unsigned long offset) -'offset' is the offset within the defined mapping region. -Accessing addresses beyond the region specified in the -creation function yields undefined results. Using an offset -which is not page aligned yields an undefined result. The -return value points to a single page in CPU address space. - -This _wc variant returns a write-combining map to the -page and may only be used with mappings created by -io_mapping_create_wc +'offset' is the offset within the defined mapping region. Accessing +addresses beyond the region specified in the creation function yields +undefined results. Using an offset which is not page aligned yields an +undefined result. The return value points to a single page in CPU address +space. -Note that the task may not sleep while holding this page -mapped. +This _wc variant returns a write-combining map to the page and may only be +used with mappings created by io_mapping_create_wc() -:: +Temporary mappings are only valid in the context of the caller. The mapping +is not guaranteed to be globaly visible. - void io_mapping_unmap_atomic(void *vaddr) +io_mapping_map_local_wc() has a side effect on X86 32bit as it disables +migration to make the mapping code work. No caller can rely on this side +effect. + +io_mapping_map_atomic_wc() has the side effect of disabling preemption and +pagefaults. Don't use in new code. Use io_mapping_map_local_wc() instead. -'vaddr' must be the value returned by the last -io_mapping_map_atomic_wc call. This unmaps the specified -page and allows the task to sleep once again. +Nested mappings need to be undone in reverse order because the mapping +code uses a stack for keeping track of them:: -If you need to sleep while holding the lock, you can use the non-atomic -variant, although they may be significantly slower. + addr1 = io_mapping_map_local_wc(map1, offset1); + addr2 = io_mapping_map_local_wc(map2, offset2); + ... + io_mapping_unmap_local(addr2); + io_mapping_unmap_local(addr1); -:: +The mappings are released with:: + + void io_mapping_unmap_local(void *vaddr) + void io_mapping_unmap_atomic(void *vaddr) + +'vaddr' must be the value returned by the last io_mapping_map_local_wc() or +io_mapping_map_atomic_wc() call. This unmaps the specified mapping and +undoes the side effects of the mapping functions. + +If you need to sleep while holding a mapping, you can use the regular +variant, although this may be significantly slower:: void *io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset) -This works like io_mapping_map_atomic_wc except it allows -the task to sleep while holding the page mapped. - +This works like io_mapping_map_atomic/local_wc() except it has no side +effects and the pointer is globaly visible. -:: +The mappings are released with:: void io_mapping_unmap(void *vaddr) -This works like io_mapping_unmap_atomic, except it is used -for pages mapped with io_mapping_map_wc. +Use for pages mapped with io_mapping_map_wc(). At driver close time, the io_mapping object must be freed:: --- a/include/linux/io-mapping.h +++ b/include/linux/io-mapping.h @@ -83,6 +83,21 @@ io_mapping_unmap_atomic(void __iomem *va } static inline void __iomem * +io_mapping_map_local_wc(struct io_mapping *mapping, unsigned long offset) +{ + resource_size_t phys_addr; + + BUG_ON(offset >= mapping->size); + phys_addr = mapping->base + offset; + return __iomap_local_pfn_prot(PHYS_PFN(phys_addr), mapping->prot); +} + +static inline void io_mapping_unmap_local(void __iomem *vaddr) +{ + kunmap_local_indexed((void __force *)vaddr); +} + +static inline void __iomem * io_mapping_map_wc(struct io_mapping *mapping, unsigned long offset, unsigned long size) @@ -101,7 +116,7 @@ io_mapping_unmap(void __iomem *vaddr) iounmap(vaddr); } -#else +#else /* HAVE_ATOMIC_IOMAP */ #include @@ -166,7 +181,18 @@ io_mapping_unmap_atomic(void __iomem *va preempt_enable(); } -#endif /* HAVE_ATOMIC_IOMAP */ +static inline void __iomem * +io_mapping_map_local_wc(struct io_mapping *mapping, unsigned long offset) +{ + return io_mapping_map_wc(mapping, offset, PAGE_SIZE); +} + +static inline void io_mapping_unmap_local(void __iomem *vaddr) +{ + io_mapping_unmap(vaddr); +} + +#endif /* !HAVE_ATOMIC_IOMAP */ static inline struct io_mapping * io_mapping_create_wc(resource_size_t base,