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Sat, 7 Jan 2023 22:58:10 +0100 (CET) Date: Sat, 7 Jan 2023 22:58:10 +0100 From: Pali =?utf-8?B?Um9ow6Fy?= To: Tom Rini 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: <20230107215810.jywdzndi46conyv5@pali> References: <20230106211408.GH3787616@bill-the-cat> <20230106214541.GI3787616@bill-the-cat> <20230106220930.pmdjzmdwyx53ouwv@pali> <20230106225156.GJ3787616@bill-the-cat> <20230107162645.2ygz5rk2tlzmiogw@pali> <20230107173212.GN3787616@bill-the-cat> <20230107173858.yq4frmhkm7ychkp5@pali> <20230107174000.GP3787616@bill-the-cat> <20230107174440.cvn7v7ylitsqkwsx@pali> <20230107174607.GQ3787616@bill-the-cat> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230107174607.GQ3787616@bill-the-cat> User-Agent: NeoMutt/20180716 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 On Saturday 07 January 2023 12:46:07 Tom Rini wrote: > On Sat, Jan 07, 2023 at 06:44:40PM +0100, Pali Rohár wrote: > > On Saturday 07 January 2023 12:40:00 Tom Rini wrote: > > > On Sat, Jan 07, 2023 at 06:38:58PM +0100, Pali Rohár wrote: > > > > On Saturday 07 January 2023 12:32:12 Tom Rini wrote: > > > > > On Sat, Jan 07, 2023 at 05:26:45PM +0100, Pali Rohár wrote: > > > > > > On Friday 06 January 2023 17:51:56 Tom Rini wrote: > > > > > > > On Fri, Jan 06, 2023 at 11:09:30PM +0100, Pali Rohár 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 Rohár wrote: > > > > > > > > > > > On Friday 06 January 2023 12:25:24 Tom Rini wrote: > > > > > > > > > > > > On Fri, Jan 06, 2023 at 05:45:43PM +0100, Pali Rohár wrote: > > > > > > > > > > > > > On Friday 06 January 2023 10:51:43 Tom Rini wrote: > > > > > > > > > > > > > > This reverts commit 777aaaa706bcfe08c284aed06886db7d482af3f8. > > > > > > > > > > > > > > > > > > > > > > > > > > > > The changes to this generic function, which is intended to help with > > > > > > > > > > > > > > 32bit platforms with large amounts of memory has unintended side effects > > > > > > > > > > > > > > (which in turn lead to boot failures) on other platforms which were > > > > > > > > > > > > > > previously functional. > > > > > > > > > > > > > > > > > > > > > > > > > > As mentioned previously, unfortunately this revert breaks 32-bit u-boot > > > > > > > > > > > > > on 36-bit mpc85xx boards with 32-bit e500v2 cores and 4GB DDR module. > > > > > > > > > > > > > > > > > > > > > > > > > > Which platforms currently have broken u-boot without this revert? The > > > > > > > > > > > > > only one which was reported is stm32mp but for it there different > > > > > > > > > > > > > workaround patch waiting in the queue. > > > > > > > > > > > > > > > > > > > > > > > > Are you able to test on one of these PowerPC platforms currently? As > > > > > > > > > > > > the stm32 problem shows, not everything is getting tested frequently > > > > > > > > > > > > enough, so how many other cases are lurking out there. And, I think > > > > > > > > > > > > overall issue is that the overflow check-and-change you introduce here > > > > > > > > > > > > should just be in the CONFIG_MAX_MEM_MAPPED==true case. As that's the > > > > > > > > > > > > case you're dealing with, yes? > > > > > > > > > > > > > > > > > > > > > > I was planning to do big retest again after all powerpc patches are > > > > > > > > > > > reviewed and merged... > > > > > > > > > > > > > > > > > > > > Yes, but can you test one of them now, to see if my idea works? > > > > > > > > > > > > > > > > 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 needed > > > > > > > > > > > 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 would be > > > > > > > > > > > no change. > > > > > > > > > > > > > > > > This is what I mean: > > > > > > > > > > > > > > > > #ifdef CONFIG_MPC85xx > > > > > > > > if (gd->ram_base + ram_size < gd->ram_base) > > > > > > > > ram_size = ...; > > > > > > > > #endif > > > > > > > > > > > > > > > > > > > I agree that this code needs to be revisited, together with ram_top > > > > > > > > > > > issue and also code which fills DDR banks. Because really mapped memory > > > > > > > > > > > for u-boot and real size of DDR are two different things here. > > > > > > > > > > > > > > > > > > > > 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 require > > > > > > > > > > special treatment. > > > > > > > > > > > > > > > > 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" = 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. > > > > > > > > > > > > > > > > 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. > > > > > > > > > > > > > > > > Fixing both issues make easily break lot of boards (if done improperly) > > > > > > > > as it touches whole u-boot code base. So not easy task. > > > > > > > > > > > > > > > > > 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. > > > > > > > > > > > > > > > > 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 > > > > > > > > > > > > > > > > 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. > > > > > > > > > > > > > > > > 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. > > > > > > > > > > > > > > > > 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). > > > > > > > > > > > > Yea, it is a mess. I'm looking at the CONFIG_MAX_MEM_MAPPED again and it > > > > > > is for different situation. CONFIG_MAX_MEM_MAPPED says maximal mapped > > > > > > memory. For mpc85xx it is by default set to 2GB for a very long time. > > > > > > And if base physical address od the RAM is at 2GB or higher then it also > > > > > > hits this 4GB limit. So CONFIG_MAX_MEM_MAPPED does not help there... > > > > > > > > > > Right, it's a mess. So, to try and end up with the least number of > > > > > broken platforms for the coming release, would you rather a full revert, > > > > > or just moving your changes under CONFIG_MAX_MEM_MAPPED being set, which > > > > > I believe you're saying is the case for 36bit PowerPC ? > > > > > > > > CONFIG_MAX_MEM_MAPPED is by default set for all powerpc boards > > > > (see arch/powerpc/include/asm/config.h) and also for some ARM plat. > > > > > > > > As I suggested above, rather move ram_size modification under > > > > CONFIG_MPC85xx which is set only for powerpc mpc85xx platform which > > > > I tested. > > > > > > > > CONFIG_MAX_MEM_MAPPED option is not too strict as CONFIG_MPC85xx. > > > > > > Right, so which option for the release on Monday do you prefer at this > > > point? We should indeed sort this mess out, for v2023.04. > > > > Just moving/hiding those changes under mpc85xx ifdef. So ARM platforms > > would be unaffected and mpc85xx platform would not break again. > > Something like this (with explanation comments): > > > > diff --git a/common/memsize.c b/common/memsize.c > > index 3c80ad2c8346..54a6416717a3 100644 > > --- a/common/memsize.c > > +++ b/common/memsize.c > > @@ -96,6 +96,7 @@ phys_size_t __weak get_effective_memsize(void) > > { > > phys_size_t ram_size = gd->ram_size; > > > > +#ifdef CONFIG_MPC85xx > > /* > > * Check for overflow and limit ram size to some representable value. > > * It is required that ram_base + ram_size must be representable by > > @@ -105,6 +106,7 @@ phys_size_t __weak get_effective_memsize(void) > > */ > > if (gd->ram_base + ram_size < gd->ram_base) > > ram_size = ((phys_size_t)~0xfffULL) - gd->ram_base; > > +#endif > > > > #ifndef CONFIG_MAX_MEM_MAPPED > > return ram_size; > > > > That works for me, can you please post it as a formal patch and I'll > apply it? I reused your commit message and I sent above patch to the list.