From patchwork Tue Apr 1 22:58:11 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 14035405 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8C8391C863F; Tue, 1 Apr 2025 22:57:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743548260; cv=none; b=UD5U5hwocgD+3DdXJ+usrtryGJzJx2iZmCOwuaXfwZKCoG5c/e46Ml5l0BbcOBCzBpjXACQJ7YU21reaRitcsye6Wi7R0j9ni5f8G8L7ohb+vfn1nIzgRdhTzUnvl4MKLbVTjvHv3+6LhCn0HtuRahcVs8m3pv+cLUc3DkOdPA4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743548260; c=relaxed/simple; bh=UyI/JP302xZqnGAVZ+H9RXsetFumokBsiWm5U/n9qhU=; h=Message-ID:Date:From:To:Cc:Subject; b=pXReRjEIgNV5a7e2NkvvzR8sINkKcgQR9ceM+1hwEoxetW6JUyk4HHzNOdZ8aa8f1CgO24UJxsL7EVhGQQ8hOTKgg8bJrmFswlbrxJmfP/pV3FwU4jM3iWT/32339I368u03H41oOrN2kTHG8sxu3XSzxAPpdf2Vrb7LXfF02RM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6300DC4CEE8; Tue, 1 Apr 2025 22:57:40 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.98) (envelope-from ) id 1tzkZ8-00000006KYG-0yQW; Tue, 01 Apr 2025 18:58:42 -0400 Message-ID: <20250401225811.008143218@goodmis.org> User-Agent: quilt/0.68 Date: Tue, 01 Apr 2025 18:58:11 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Linus Torvalds , Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Vincent Donnefort , Vlastimil Babka , Mike Rapoport , Jann Horn Subject: [PATCH v5 0/4] tracing: Clean up persistent ring buffer code Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Now that I learned that the memory passed back from reserve_mem is part of the memory allocator and just "reserved" and the memory is already virtually mapped, it can simply use phys_to_virt() on the physical memory that is returned to get the virtual mapping for that memory! (Thanks Mike!) That makes things much easier, especially since it means that the memory returned by reserve_mem is no different than the memory retrieved by page_alloc(). This allows that memory to be memory mapped to user space no differently than it is mapped by the normal buffer. This new series does the following: - Enforce the memory mapping is page aligned (both the address and the size). If not, it errors out. - Use phys_to_virt() to get to the virtual memory from the reserve_mem returned addresses. As the memory is already freed via reserve_mem_release_by_name() and it's not mapped by vmap() anymore, the free ring buffer code doesn't need to do anything special for this mapping. - Treat the buffer allocated via memmap differently. It still needs to be virtually mapped (cannot use phys_to_virt) and it must not be freed nor memory mapped to user space. A new flag is added when a buffer is created this way to prevent it from ever being memory mapped to user space and the ref count is upped so that it can never be freed. - Use vmap_page_range() instead of using kmalloc_array() to create an array of struct pages for vmap(). - Use flush_kernel_vmap_range() instead of flush_dcache_folio() Changes since v4: https://lore.kernel.org/linux-trace-kernel/20250401215115.602501043@goodmis.org/ - Fixed calling free_reserve_area() twice on the same memory Steven Rostedt (4): tracing: Enforce the persistent ring buffer to be page aligned tracing: Have reserve_mem use phys_to_virt() and separate from memmap buffer tracing: Use vmap_page_range() to map memmap ring buffer ring-buffer: Use flush_kernel_vmap_range() over flush_dcache_folio() ---- Documentation/admin-guide/kernel-parameters.txt | 2 + Documentation/trace/debugging.rst | 2 + kernel/trace/ring_buffer.c | 5 +- kernel/trace/trace.c | 68 ++++++++++++++++--------- kernel/trace/trace.h | 1 + 5 files changed, 52 insertions(+), 26 deletions(-)