From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lamorak.hansenpartnership.com (lamorak.hansenpartnership.com [198.37.111.173]) (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 B845C34BA35; Sun, 5 Oct 2025 14:29:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.37.111.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759674563; cv=none; b=uiZrEJNcwglyG1LWq4StQgEdYYXqM/Mx+N1gDrG+CCRCxXbvI94Mgm7k9NVcVLi212ZtOUtzPpvsgr/4GjCyMm4XaoFxSG00esK6oJKqfnbbb2Z2JmWzmKOG+VGKx5AJDhndhO+DKTNKYtmfF6sBTfVFuu23ZYVtZaSj4RVJpMI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759674563; c=relaxed/simple; bh=hrsv2YDzWLNG7Ngtd7/6UjmmDS9vVj1AT8usgE7qgQI=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=MyOFYMGbedAHDbo4fPt4/g8yt0APtU7Yp269uT8dA+q3c1gJrAVMOFUqjVEB02Jt7dlOMXVLQXPz2BZUhQshv90Qii02SrjOgDCAbvdLUz2KktnmAH+9dRKhDfF329PVkO1pw//m3sF52TS6Y0EKNYZDpY3d8n8hfZkTX7OahRw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=HansenPartnership.com; spf=pass smtp.mailfrom=HansenPartnership.com; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b=Xjfl0yNW; arc=none smtp.client-ip=198.37.111.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=HansenPartnership.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=HansenPartnership.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="Xjfl0yNW" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1759674560; bh=hrsv2YDzWLNG7Ngtd7/6UjmmDS9vVj1AT8usgE7qgQI=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References:From; b=Xjfl0yNWvNlgfTU8/EAtoWEJVM/U3ViTlMzofQd5PTmLzm6zW9WheCJfZQBWMf/Sx PS4SvfONhUji+BpjFDo64XZP9T6ZIhKXhywCfLN/UQS3ZvwBWm/hIyqdey/rZSYGFE L93/5IM0KbGEcCMPzv6xPzkYlBejcfGaIgzTmGwQ= Received: from lingrow.int.hansenpartnership.com (unknown [IPv6:2601:5c4:4302:c21::a774]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519) (No client certificate requested) by lamorak.hansenpartnership.com (Postfix) with ESMTPSA id A7B691C0096; Sun, 05 Oct 2025 10:29:19 -0400 (EDT) Message-ID: Subject: Re: [PATCH v1 3/9] parisc: Convert DMA map_page to map_phys interface From: James Bottomley To: John David Anglin , Jason Gunthorpe , Leon Romanovsky Cc: Marek Szyprowski , Leon Romanovsky , Andreas Larsson , Borislav Petkov , Dave Hansen , "David S. Miller" , Geoff Levand , Helge Deller , Ingo Molnar , iommu@lists.linux.dev, Jason Wang , Juergen Gross , linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Madhavan Srinivasan , Matt Turner , Michael Ellerman , "Michael S. Tsirkin" , Richard Henderson , sparclinux@vger.kernel.org, Stefano Stabellini , Thomas Bogendoerfer , Thomas Gleixner , virtualization@lists.linux.dev, x86@kernel.org, xen-devel@lists.xenproject.org, Magnus Lindholm Date: Sun, 05 Oct 2025 10:29:19 -0400 In-Reply-To: <610b10bc-1aa2-4fad-a40b-be5fcfa04430@bell.net> References: <333ec4dabec16d3d913a93780bc6e7ddb5240fcf.1759071169.git.leon@kernel.org> <20251003150144.GC3360665@nvidia.com> <610b10bc-1aa2-4fad-a40b-be5fcfa04430@bell.net> Autocrypt: addr=James.Bottomley@HansenPartnership.com; prefer-encrypt=mutual; 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8mT2Eh9SkH+YVOmaKsajgZgrBxA7fWmGoxXswEVxJIFj3vW7yNc0C5HaUdYa5iGOMs4kg2ht4s7yy7NRQuh7BifWjo6BQ6k4S1H+6axZucxhSV1L6zN9d+lr3Xo/vy1unzA== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: linux-alpha@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2025-10-03 at 13:18 -0400, John David Anglin wrote: > On 2025-10-03 11:01 a.m., Jason Gunthorpe wrote: > > This doesn't actually use the virt at all: > >=20 > > offset =3D ((unsigned long) addr) & ~IOVP_MASK; > > if((size % L1_CACHE_BYTES) || ((unsigned long)addr % > > L1_CACHE_BYTES)) > > ccio_io_pdir_entry(pdir_start, KERNEL_SPACE, > > (unsigned long)addr, hint); > >=20 > > And ccio_io_pdir_entry(): > > pa =3D lpa(vba); > >=20 > > Is a special instruction that uses virt but AI tells me that > > special LPA instruction is returning phys. Not sure if that is a > > different value than virt_to_phys().. >=20 > ccio_io_pdir_entry currently only supports KERNEL_SPACE. Actually there's a bit more nuance to it than that. Obviously DMA has to support user pages otherwise I/O wouldn't work. The way it does is that all physical pages are mapped in the kernel and we try to make sure all user mappings are on cache stride (4MB) boundaries so the coherence index of the kernel virtual address and the user virtual address are the same, so we can solely use the kernel virtual address to calculate the coherence index for the IOMMU. If that's not true, we flush the user virtual address range in gup and the kernel virtual address range before sending the I/O completion. Regards, James