Date: Wed, 26 Jan 2011 09:38:27 -0600 From: Mark Tinguely <marktinguely@gmail.com> To: Devesh Rai <deveshkr@marvell.com> Cc: "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org> Subject: Re: Changing virtual adress space layout Message-ID: <4D403FF3.7010500@gmail.com> In-Reply-To: <0DB595A2CB707F458400BE9663B6A7225E42E359C8@SC-VEXCH2.marvell.com> References: <0DB595A2CB707F458400BE9663B6A7225E42E359C8@SC-VEXCH2.marvell.com>
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Reading your reply, it sounds like you want to directly map a full 1GB to the KVA. The upper 1GB will always be partially used; for example it has HIGH_VECTOR, and device mappings. So it sounds like you should set KERNBASE to 0x8000_0000, map the RAM at 0x8000_0000 and leave the KERNVIRTADDR where is was. The 1GB memory should be physically contiguous and properly aligned, so you be able to directly add the addresses into the KVA "level 1 pagetable entries" either manually or with pmap_map_chunk(). Sorry, I do not have my development machine, so I can't do the background work. Does changing the KERNBASE into a makeoption really overriding the static define in /sys/arm/include/vm_machdep.h? A "cc -E" (for example initarm() source file) would answer that question. The other place to look would be in /sys/conf, but after a quick look, I did not see any hardcoded values in the ARM specific files. Also, the KERNVIRTADDR does not equal KERNBASE on many ARM platforms ; the boot loader may have put the kernel text at an offset to pass parameters, and some older families use the ARM_USE_SMALL_ALLOC feature - a form of direct ARM pagetable map. For example, the Sheeva port has the KERNPHYSADDR/KERNVIRTADDR at 0x00900000/0xc0900000. --Mark. On 1/26/2011 8:34 AM, Devesh Rai wrote: > > Hi Mark, > > Actually I want to map large portion of RAM in kernel virtual address space. > To achieve this in Linux, I did following > > 1) boot kernel with 256M by setting CONFIG_CMDLINE="mem=256M". This freed up more than 1GB of RAM for my module usages > 2) increase KVA to 3GB by setting CONFIG_VMSPLIT_1G=y ( 1G for user and 3GB for kernel) > 3) ioremap unused RAM ( 2GB - 256MB ) into Kernel virtual address space. > > Changing KERNBASE and KERNVIRTADDR "makeoption" from 0xc0000000 to 0x80000000 did not worked for me. Kernel hang while loading. > > Thanks& Regards > Devesh > > -----Original Message----- > From: Mark Tinguely [mailto:marktinguely@gmail.com] > Sent: Thursday, January 13, 2011 10:00 PM > To: freebsd-arm@freebsd.org > Cc: Devesh Rai > Subject: Re: Changing virtual adress space layout > > On 1/13/2011 1:30 AM, Devesh Rai wrote: >> Hi, >> >> I am new to FreeBSD. Can some tell how to change virtual address space layout in FreeBSD for arm? >> For x86, KVA_PAGES=N option is there in FreeBSD. In Linux, I used CONFIG_VMSPLIT option. >> I am looking corresponding option for arm. >> >> Regards >> Devesh > I assume you have run out of space for the device virtual addresses. > > KERNBASE is hard coded in sys/arm/include/vm_param.h to be 0xc0000000. > > There is a related variable for each device configuration: the > KERNVIRTADDR "option" and "makeoption" values. This is usually in one > of the "std" file file for the device. KERNVIRTADDR sets the starting > location of the executable and is sometimes different than KERNBASE. > > The arm code does not map the from KERNBASE to 0xffff_ffff into the KVA. > Instead, there is a variable that determines the maximum size of the > kernel executable and kernel virtual address area. Above this defined > area lies the no-cache remap memory region, device map area, high > vector, etc. > > On a tangent note: There will be a great advantage in ARMv6/ARMv7 to go > to a 2GB UVA / 2GB KVA. > > --Mark. >
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