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[2603:6081:7b00:6400:9162:adb5:1773:34c0]) by smtp.gmail.com with ESMTPSA id cm8-20020a05622a250800b003a50ef44a77sm1124287qtb.28.2023.01.06.14.51.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Jan 2023 14:51:58 -0800 (PST) Date: Fri, 6 Jan 2023 17:51:56 -0500 From: Tom Rini To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: u-boot@lists.denx.de, Marek Vasut , Patrick Delaunay Subject: Re: [PATCH] Revert "common/memsize.c: Fix get_effective_memsize() to check for overflow" Message-ID: <20230106225156.GJ3787616@bill-the-cat> References: <20230106155143.4025812-1-trini@konsulko.com> <20230106164543.3gtq73flpoocg7mc@pali> <20230106172524.GE3787616@bill-the-cat> <20230106202256.bvjwcfsjbhzsfgrh@pali> <20230106211408.GH3787616@bill-the-cat> <20230106214541.GI3787616@bill-the-cat> <20230106220930.pmdjzmdwyx53ouwv@pali> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="6MYBY5cT6WM736SS" Content-Disposition: inline In-Reply-To: <20230106220930.pmdjzmdwyx53ouwv@pali> X-Clacks-Overhead: GNU Terry Pratchett X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.39 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.103.6 at phobos.denx.de X-Virus-Status: Clean --6MYBY5cT6WM736SS Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jan 06, 2023 at 11:09:30PM +0100, Pali Roh=E1r wrote: > On Friday 06 January 2023 16:45:41 Tom Rini wrote: > > On Fri, Jan 06, 2023 at 04:14:08PM -0500, Tom Rini wrote: > > > On Fri, Jan 06, 2023 at 09:22:56PM +0100, Pali Roh=E1r wrote: > > > > On Friday 06 January 2023 12:25:24 Tom Rini wrote: > > > > > On Fri, Jan 06, 2023 at 05:45:43PM +0100, Pali Roh=E1r wrote: > > > > > > On Friday 06 January 2023 10:51:43 Tom Rini wrote: > > > > > > > This reverts commit 777aaaa706bcfe08c284aed06886db7d482af3f8. > > > > > > >=20 > > > > > > > The changes to this generic function, which is intended to he= lp with > > > > > > > 32bit platforms with large amounts of memory has unintended s= ide effects > > > > > > > (which in turn lead to boot failures) on other platforms whic= h were > > > > > > > previously functional. > > > > > >=20 > > > > > > As mentioned previously, unfortunately this revert breaks 32-bi= t u-boot > > > > > > on 36-bit mpc85xx boards with 32-bit e500v2 cores and 4GB DDR m= odule. > > > > > >=20 > > > > > > Which platforms currently have broken u-boot without this rever= t? The > > > > > > only one which was reported is stm32mp but for it there differe= nt > > > > > > workaround patch waiting in the queue. > > > > >=20 > > > > > Are you able to test on one of these PowerPC platforms currently?= As > > > > > the stm32 problem shows, not everything is getting tested frequen= tly > > > > > enough, so how many other cases are lurking out there. And, I th= ink > > > > > overall issue is that the overflow check-and-change you introduce= here > > > > > should just be in the CONFIG_MAX_MEM_MAPPED=3D=3Dtrue case. As t= hat's the > > > > > case you're dealing with, yes? > > > >=20 > > > > I was planning to do big retest again after all powerpc patches are > > > > reviewed and merged... > > >=20 > > > Yes, but can you test one of them now, to see if my idea works? >=20 > Ok, I will try to look at during the weekend. OK, good, thanks. > > > > Anyway, if the issue here is with ram_size and its reduction was ne= eded > > > > for mpc85xx (at the time of introduction of that patch), what about > > > > putting mpc85xx ifdef around ram_size reduction? For arm boards it = would > > > > have same behavior as revert of that commit and for mpc85xx it woul= d be > > > > no change. >=20 > This is what I mean: >=20 > #ifdef CONFIG_MPC85xx > if (gd->ram_base + ram_size < gd->ram_base) > ram_size =3D ...; > #endif >=20 > > > > I agree that this code needs to be revisited, together with ram_top > > > > issue and also code which fills DDR banks. Because really mapped me= mory > > > > for u-boot and real size of DDR are two different things here. > > >=20 > > > The issue here is that we see two now (given Fabio's reminder about > > > another thread I had forgotten) of unintended consequences, on 32bit > > > platforms trying to normally have 2GB of memory, which does not requi= re > > > special treatment. >=20 > Running git grep get_effective_memsize and git grep 'gd->ram_top' shows > the root of this issue: Different platforms, boards and common code use > these things differently. This needs to be "fixed" =3D unified in whole > codebase. We need a function which returns mappable memory for u-boot > (intptr_t type is enough) and another function (or structure or > whatever) which says total size of RAM as u64 type (to ensure that it > would work also for 4GB SODIMM modules on pure 32-bit platforms). And > then each place in u-boot code has to be modified to use the correct > function. >=20 > Second issue is then gd->ram_top. Either say 4GB for 32-bit ram_top type > is not supported or say that zero value is special and represents 4GB. > And also every place in u-boot code needs to be adjusted by this > decision / code. >=20 > Fixing both issues make easily break lot of boards (if done improperly) > as it touches whole u-boot code base. So not easy task. >=20 > > What I'm leaning towards right now even, is that since it's hard to test > > the non-36bit platforms that do set CONFIG_MAX_MEM_MAPPED, to see if > > their behavior also changed here, the 36bit platforms should just be > > overriding get_effective_memsize. >=20 > There are (at least) 3 situation: > 1) if RAM is mapped to the end of physical address space (possibly just > small e.g. 1GB) > 2) if platform is >32-bit but running in 32-bit mode (so physical > address is u64 because we do not have e.g. int36_t; but void* is > 32-bit) > 3) if RAM is exactly 4GB and u-boot is 32-bit >=20 > And every one has different edge cases and cause different problems. > Now, as I pointed above that every platform / board is using > get_effective_memsize() differently, plus we have CONFIG_MAX_MEM_MAPPED > option, it means that number of test matrix is really huge. >=20 > It looks like that ARM issues are caused by the fact that RAM is mapped > to the end of the physical address space (so it does not matter how big > or small it is). And powerpc issue is 4GB of RAM together with running > in 32-bit mode. >=20 > Anyway, has U-Boot support for 32-bit x86 CPUs with PAE support? If yes, > then I bet that there can be other edge cases when e.g. 8GB of DDR is > connected. Yes, it's very much a mess, so for this release I'd like to return to either: - Status quo of v2022.10 (revert this patch) - Change only CONFIG_MAX_MEM_MAPPED being set behavior (should keep PowerPC 36bit working, may have unexpected impact on other platforms, still, but very few at least). --=20 Tom --6MYBY5cT6WM736SS Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQGzBAABCgAdFiEEGjx/cOCPqxcHgJu/FHw5/5Y0tywFAmO4pgkACgkQFHw5/5Y0 tyydSgv/X29fdNgWJ+buUNayI36rB5nM6AuNM+e5V51XI98fnhzJXCDLT2GYGIq0 3BYS9/8Ib+gmlKyoVXh8812cGZ27ujS+Lh9s6XQYVNVqPHMKH+WYQk6ADQiW29bC w2eMu2+nGY52z0GlWZaFcmPK0+dYPYdiHuZ8wIfY+twOUQQHvbHq7noHfvA9Co1F IcjkFE2ccGn7EEs2N2r9VMexrQYk0c7bzVkx/zgJiag1F7myiV/MS7pWvZituUl+ w5eylPbqK1hcnxPjHvT3eXRX+fIm1Q1/VH2E6vnZ3t9WLoTk7vxnT5C1sRqZbJZS m9kxfH6mgEDS3ZQmO2qDz50Ga3jk+a8r783uMoh84jn01Y7GoKl1sK4cKfUWbZYE //a1pbKqzJIR1UvMKemN79f80AlEhRH75udJ8t61iJtu+Op5FA4vt2I3ECfZcqVc /RNKq/rp7pXb3S/AXweCGGeDk2roPed+XknE4IAJxffzdJVAnW40dOHNij4I30s2 fqfkN+Oc =oLBe -----END PGP SIGNATURE----- --6MYBY5cT6WM736SS--