From mboxrd@z Thu Jan 1 00:00:00 1970 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 1BA7D79FE; Tue, 1 Apr 2025 17:58:51 +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=1743530332; cv=none; b=YSmYef53D8x/M9ehAr+02cmbfUHAj4ZOSFMfxB2/GQwRn558j79DOgM8rnOZOXpXWd9qXxKE0JOPplXgAx8beoRTuXGXRsMtOM56rLEdmeul88KZgvEuW+TxriDuwu6YPrsAePSYShO94T0qUAupOm5NnvkZ51NHFzkHNeaCvfM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743530332; c=relaxed/simple; bh=wiGocuCPvltfWWje9XoaBmB3Bty+R3cKGynKNs7ru6w=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RGy60X+37DNounJG7mG6nJwXw0Xz5egudQ8pLbCmOIXsnmJO8GK7/tNRId5USuZ9Ck+Es8oxi2I+oJwLF3IGfYIDV72HqokSxhaXAXe5AjSjPYP5MWwDRgIR7UIvaX6XpsYfSV7l7R9m6ZetArYYy8nxlNEBDOiOkBoEqbeUT4U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OOtMo4dh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OOtMo4dh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0B847C4CEE4; Tue, 1 Apr 2025 17:58:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743530331; bh=wiGocuCPvltfWWje9XoaBmB3Bty+R3cKGynKNs7ru6w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OOtMo4dhzFu0UvTT47V/tlPt5W8cfdYm5/embeWyUCu1HaA6a2kSi5ThOvHBljjRm bkBw+2mIDvULCHj/BwF58PBcs4dT3WyJCVMYpbn0u1k9wkYyZoHtLUzEMmFzJrWeaR qJQAEYLw1tl5Y536VjSqvyLC2TfGXUusJDXZtFE+JhD0YlIfLTSS07po2r8xib9i5h rDUhOUqIV04EmDSOM75nnnT/KPY7Y2vjU72lDmhL73doeH6H/qqBziRRK4OCHMf9Z4 KuG6COmbw9YZb715l0YWi9HJMY+I44yVf9UhuJPLERuadLEjk/05QKRxBPAr6MGZOo 5TDsSfyFGoBEQ== Date: Tue, 1 Apr 2025 20:58:43 +0300 From: Mike Rapoport To: Steven Rostedt Cc: Linus Torvalds , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Vincent Donnefort , Vlastimil Babka , Kees Cook , Tony Luck , "Guilherme G. Piccoli" , linux-hardening@vger.kernel.org Subject: Re: [PATCH v2 1/2] tracing: ring-buffer: Have the ring buffer code do the vmap of physical memory Message-ID: References: <20250331143532.459810712@goodmis.org> <20250331133906.48e115f5@gandalf.local.home> <20250331165801.715aba48@gandalf.local.home> <20250401111159.7632a0fa@gandalf.local.home> <20250401115423.3b6a926d@gandalf.local.home> Precedence: bulk X-Mailing-List: linux-trace-kernel@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: <20250401115423.3b6a926d@gandalf.local.home> On Tue, Apr 01, 2025 at 11:54:23AM -0400, Steven Rostedt wrote: > On Tue, 1 Apr 2025 18:26:43 +0300 > Mike Rapoport wrote: > > > > But if I use vmap_page_range(), how do I give that back to the memory allocator? > > > > But you don't need neither vmap() nor vmap_page_range() to have kernel page > > tables for memory that you get from reserve_mem. It's already mapped and > > plain phys_to_virt() gives you the virtual address you can use. > > Oh! That makes things so much easier! Especially since that means it should > work like the normal buffer where virt_to_page() should also work. Right? Right. > Now I do support mapping the persistent ring buffer via memmap, but I can > just give up on allowing that to be memory mapped to user space, or even > freed. It can't be freed without jumping through some hoops, and mapping it to user space is hassle as well. -- Sincerely yours, Mike.