From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC PATCH v8 07/14] arm64/mm, xpfo: temporarily map dcache regions References: <20190214155435.GA15694@cisco> From: Khalid Aziz Message-ID: <92787149-bb9e-6ee9-6d04-431ec145e9a4@oracle.com> Date: Thu, 14 Feb 2019 10:29:52 -0700 MIME-Version: 1.0 In-Reply-To: <20190214155435.GA15694@cisco> Content-Type: multipart/mixed; boundary="------------831B727C76672501BCC5E3E8" To: Tycho Andersen Cc: juergh@gmail.com, jsteckli@amazon.de, ak@linux.intel.com, torvalds@linux-foundation.org, liran.alon@oracle.com, keescook@google.com, akpm@linux-foundation.org, mhocko@suse.com, catalin.marinas@arm.com, will.deacon@arm.com, jmorris@namei.org, konrad.wilk@oracle.com, Juerg Haefliger , deepa.srinivasan@oracle.com, chris.hyser@oracle.com, tyhicks@canonical.com, dwmw@amazon.co.uk, andrew.cooper3@citrix.com, jcm@redhat.com, boris.ostrovsky@oracle.com, kanth.ghatraju@oracle.com, joao.m.martins@oracle.com, jmattson@google.com, pradeep.vincent@oracle.com, john.haxby@oracle.com, tglx@linutronix.de, kirill.shutemov@linux.intel.com, hch@lst.de, steven.sistare@oracle.com, labbott@redhat.com, luto@kernel.org, dave.hansen@intel.com, peterz@infradead.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org List-ID: This is a multi-part message in MIME format. --------------831B727C76672501BCC5E3E8 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 2/14/19 8:54 AM, Tycho Andersen wrote: > Hi, >=20 > On Wed, Feb 13, 2019 at 05:01:30PM -0700, Khalid Aziz wrote: >> From: Juerg Haefliger >> >> If the page is unmapped by XPFO, a data cache flush results in a fatal= >> page fault, so let's temporarily map the region, flush the cache, and = then >> unmap it. >> >> v6: actually flush in the face of xpfo, and temporarily map the underl= ying >> memory so it can be flushed correctly >> >> CC: linux-arm-kernel@lists.infradead.org >> Signed-off-by: Juerg Haefliger >> Signed-off-by: Tycho Andersen >> --- >> arch/arm64/mm/flush.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c >> index 30695a868107..fad09aafd9d5 100644 >> --- a/arch/arm64/mm/flush.c >> +++ b/arch/arm64/mm/flush.c >> @@ -20,6 +20,7 @@ >> #include >> #include >> #include >> +#include >> =20 >> #include >> #include >> @@ -28,9 +29,15 @@ >> void sync_icache_aliases(void *kaddr, unsigned long len) >> { >> unsigned long addr =3D (unsigned long)kaddr; >> + unsigned long num_pages =3D XPFO_NUM_PAGES(addr, len); >> + void *mapping[num_pages]; >=20 > What version does this build on? Presumably -Wvla will cause an error > here, but, >=20 >> if (icache_is_aliasing()) { >> + xpfo_temp_map(kaddr, len, mapping, >> + sizeof(mapping[0]) * num_pages); >> __clean_dcache_area_pou(kaddr, len); >=20 > Here, we map the pages to some random address via xpfo_temp_map(), > then pass the *original* address (which may not have been mapped) to > __clean_dcache_area_pou(). So I think this whole approach is wrong. >=20 > If we want to do it this way, it may be that we need some > xpfo_map_contiguous() type thing, but since we're just going to flush > it anyway, that seems a little crazy. Maybe someone who knows more > about arm64 knows a better way? >=20 > Tycho >=20 Hi Tycho, You are right. Things don't quite look right with this patch. I don't know arm64 well enough either, so I will wait for someone more knowledgeable to make a recommendation here. On a side note, do you mind if I update your address in your signed-off-by from tycho@docker.com when I send the next version of this series? 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