Date: Sun, 08 Jun 2008 00:39:43 -0500 From: Alan Cox <alc@cs.rice.edu> To: Kostik Belousov <kostikbel@gmail.com> Cc: hackers@freebsd.org Subject: Re: Increasing KVM on amd64 Message-ID: <484B709F.1070503@cs.rice.edu> In-Reply-To: <20080608052653.GS94309@deviant.kiev.zoral.com.ua> References: <484B20E7.2040009@cs.rice.edu> <20080608052653.GS94309@deviant.kiev.zoral.com.ua>
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Kostik Belousov wrote: >On Sat, Jun 07, 2008 at 06:59:35PM -0500, Alan Cox wrote: > > >>You can download a patch from >>http://www.cs.rice.edu/~alc/amd64_kvm_6GB.patch that increases amd64's >>kernel virtual address space to 6GB. This patch also increases the >>default for the kmem map to almost 2GB. I believe that kernel loadable >>modules still work. However, I suspect that mini-dumps are broken. >> >> >The amd64 modules text/data/bss virtual addresses are allocated from the >kernel_map (link_elf_obj.c, link_elf_load_file). Now, the lower end >of the kernel_map is top-6Gb. > >Kernel code (both kernel proper and modules) is compiled for "kernel memory >model", according to the gcc info: >`-mcmodel=kernel' >Generate code for the kernel code model. The kernel runs in the >negative 2 GB of the address space. This model has to be used for >Linux kernel code. > >I suspect we have a problem there. > > > The change to link_elf_obj.c is supposed to ensure allocation of an address in the upper 2GB of the kernel map for the module. Alan
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