From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794725231; b=X+uS+SuZZO3MnAvFPPqnuIllrEGKAS4LNh2HecQNbsSBitYhyWEppLbsY7mXrdK5epaX sLcTSId3Z9w9EyL/dal0sd6qm9QvTxB+i15FuY2M4vmUos2pBjexVtNoOTZcXnI4eDR7J p2lB6LhVA3kIn2GT9ecmUantLYs/KxfnDeIkEtHS00HwFEMYEau5cHFuBLJKV6thy53fF cCx+/0gg5lkjEqgJNDpY8kBDME0p4VVlSK0S1LXdBmIsYpbD29U8UbOc9UVZtgGbxzYdJ MD7LZcC153LBiUFMAkB9Qqhw5TjhcsC8NwURJbrbE6h4/R2LYoAYJvmJYJeJHqE1xiQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794725231; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition: Content-Transfer-Encoding:In-Reply-To; bh=jwh2VnCoRYNWSpJavB3/olcfSK9xBV/jM+pUQtOBE9A=; b=MQj4x0f93NLG+Nio/zPbKHTO/lrNmLaCL8PbQl8dcBNO2GtiQV87WEmhhUEXmPTqM9kQ UWTDCxqxard2a1/BiRqsUwGb0e3NoRx0JQs+r1o3UGo46mOIlM4Y6ba7V/PUUygKBxiew gQ/HlPV1eolQ852eixnYVKfL8UbZyFAaZQ5XM9ywO++4SKDN/J3pKK+Wy8kj9ozaf4lZX UUL+Fz9ccR01ijRaOySbAELBtz3hxvcNGMWZB402YnHyUcwp8FDAZ0wQ43IHNXPQ78vQ9 gtROySToA/A76UJpKk2c5jE6mkrZiez+z2A4UmP9wTpvLwx7p9zvVR9yoR666ObMlWw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=iQc88LIF; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 74D15606A329; Sun, 15 Nov 2026 06:47:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=iQc88LIF Received: by smtp.kernel.org (Postfix) with ESMTPSA id 168E31F000C4; Sun, 15 Nov 2026 06:47:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794725231; bh=jwh2VnCoRYNWSpJavB3/olcfSK9xBV/jM+pUQtOBE9A=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=iQc88LIFJYlWRk3x+jUkZv57DqD6Zr+Qi/bjvEAx6dsX0FyX0S6lwk5ssflsR/o8q L14BShrB8yCWC1qdswhGpATgsyOV8akcA3ZMu/82XdeGgiJt/9OF9kPNqo+YMkfT57 Cda8LpkOvH59RGcnzmo/VfwIa1Myl3kIXSPqFx/aZY5QuFYwzhZ9/jc2VoG3eh44ip 0ZeYVP9n/yUTogA4bJF/Jo01UXxbS8p1XgamlSKGMQnAbXpw6/Aa2iM0N1gdgBDnKe qRiQYpm/Lla8FEkImBmQmUc2AiqKt61MV+5B7glgUOmoOp8jSZa0TfUzpuB2cjqTCx M83DKc/z/VjxQ== Date: Sun, 15 Nov 2026 08:47:03 +0200 From: Mike Rapoport To: Ivan Ezequiel Rodriguez Cc: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm: use PFN_PHYS() in phys_mem_access_prot() Message-ID: References: <20261113193812.1239880-1-ivanrwcm25@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20261113193812.1239880-1-ivanrwcm25@gmail.com> On Fri, Nov 13, 2026 at 04:38:12PM -0300, Ivan Ezequiel Rodriguez wrote: > From: Iván Ezequiel Rodriguez > > phys_mem_access_prot() stores "pfn << PAGE_SHIFT" in a phys_addr_t. > The shift is evaluated as unsigned long, so on a 32-bit kernel with > CONFIG_PHYS_ADDR_T_64BIT an address above 4 GiB is truncated before > uncached_access() compares it with __pa(high_memory). > > mmap_mem_prepare() already shifts in phys_addr_t, so the mapping is > accepted and then left cacheable. PFN_PHYS() casts before the shift. > > On a MIPS32 XPA Malta guest, mmap of /dev/mem at 0xf00000000 without > O_DSYNC used the boot CCA. The same mapping with O_DSYNC was uncached. > With PFN_PHYS() both are uncached. > > Fixes: 7e6735c3578e ("/dev/mem: use phys_addr_t for physical addresses") > Cc: stable@vger.kernel.org > Signed-off-by: Iván Ezequiel Rodriguez Reviewed-by: Mike Rapoport (Microsoft) > --- > mm/char-mem.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/char-mem.c b/mm/char-mem.c > index c5761ddedbd7..53ce0034a4c1 100644 > --- a/mm/char-mem.c > +++ b/mm/char-mem.c > @@ -272,7 +272,7 @@ static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn, > unsigned long size, pgprot_t vma_prot) > { > #ifdef pgprot_noncached > - phys_addr_t offset = pfn << PAGE_SHIFT; > + phys_addr_t offset = PFN_PHYS(pfn); > > if (uncached_access(file, offset)) > return pgprot_noncached(vma_prot); > -- > 2.43.0 > -- Sincerely yours, Mike.