lwn.git/arch/i386/kernel/vmlinux.lds.S, branch docs-next

i386: move kernel

2007-10-11T09:17:01+00:00

Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar

i386: prepare shared kernel/vmlinux.lds.S

2007-10-11T09:12:11+00:00

Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar

i386: Put allocated ELF notes in read-only data segment

2007-07-19T17:04:47+00:00

This changes the i386 linker script and the asm-generic macro it uses so that ELF note sections with SHF_ALLOC set are linked into the kernel image along with other read-only data. The PT_NOTE also points to their location. This paves the way for putting useful build-time information into ELF notes that can be found easily later in a kernel memory dump. Signed-off-by: Roland McGrath Cc: Andi Kleen Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Martin Schwidefsky Cc: Heiko Carstens Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

define new percpu interface for shared data

2007-07-19T17:04:44+00:00

per cpu data section contains two types of data. One set which is exclusively accessed by the local cpu and the other set which is per cpu, but also shared by remote cpus. In the current kernel, these two sets are not clearely separated out. This can potentially cause the same data cacheline shared between the two sets of data, which will result in unnecessary bouncing of the cacheline between cpus. One way to fix the problem is to cacheline align the remotely accessed per cpu data, both at the beginning and at the end. Because of the padding at both ends, this will likely cause some memory wastage and also the interface to achieve this is not clean. This patch: Moves the remotely accessed per cpu data (which is currently marked as ____cacheline_aligned_in_smp) into a different section, where all the data elements are cacheline aligned. And as such, this differentiates the local only data and remotely accessed data cleanly. Signed-off-by: Fenghua Yu Acked-by: Suresh Siddha Cc: Rusty Russell Cc: Christoph Lameter Cc: Cc: "Luck, Tony" Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

xen: Core Xen implementation

2007-07-18T15:47:42+00:00

This patch is a rollup of all the core pieces of the Xen implementation, including: - booting and setup - pagetable setup - privileged instructions - segmentation - interrupt flags - upcalls - multicall batching BOOTING AND SETUP The vmlinux image is decorated with ELF notes which tell the Xen domain builder what the kernel's requirements are; the domain builder then constructs the address space accordingly and starts the kernel. Xen has its own entrypoint for the kernel (contained in an ELF note). The ELF notes are set up by xen-head.S, which is included into head.S. In principle it could be linked separately, but it seems to provoke lots of binutils bugs. Because the domain builder starts the kernel in a fairly sane state (32-bit protected mode, paging enabled, flat segments set up), there's not a lot of setup needed before starting the kernel proper. The main steps are: 1. Install the Xen paravirt_ops, which is simply a matter of a structure assignment. 2. Set init_mm to use the Xen-supplied pagetables (analogous to the head.S generated pagetables in a native boot). 3. Reserve address space for Xen, since it takes a chunk at the top of the address space for its own use. 4. Call start_kernel() PAGETABLE SETUP Once we hit the main kernel boot sequence, it will end up calling back via paravirt_ops to set up various pieces of Xen specific state. One of the critical things which requires a bit of extra care is the construction of the initial init_mm pagetable. Because Xen places tight constraints on pagetables (an active pagetable must always be valid, and must always be mapped read-only to the guest domain), we need to be careful when constructing the new pagetable to keep these constraints in mind. It turns out that the easiest way to do this is use the initial Xen-provided pagetable as a template, and then just insert new mappings for memory where a mapping doesn't already exist. This means that during pagetable setup, it uses a special version of xen_set_pte which ignores any attempt to remap a read-only page as read-write (since Xen will map its own initial pagetable as RO), but lets other changes to the ptes happen, so that things like NX are set properly. PRIVILEGED INSTRUCTIONS AND SEGMENTATION When the kernel runs under Xen, it runs in ring 1 rather than ring 0. This means that it is more privileged than user-mode in ring 3, but it still can't run privileged instructions directly. Non-performance critical instructions are dealt with by taking a privilege exception and trapping into the hypervisor and emulating the instruction, but more performance-critical instructions have their own specific paravirt_ops. In many cases we can avoid having to do any hypercalls for these instructions, or the Xen implementation is quite different from the normal native version. The privileged instructions fall into the broad classes of: Segmentation: setting up the GDT and the GDT entries, LDT, TLS and so on. Xen doesn't allow the GDT to be directly modified; all GDT updates are done via hypercalls where the new entries can be validated. This is important because Xen uses segment limits to prevent the guest kernel from damaging the hypervisor itself. Traps and exceptions: Xen uses a special format for trap entrypoints, so when the kernel wants to set an IDT entry, it needs to be converted to the form Xen expects. Xen sets int 0x80 up specially so that the trap goes straight from userspace into the guest kernel without going via the hypervisor. sysenter isn't supported. Kernel stack: The esp0 entry is extracted from the tss and provided to Xen. TLB operations: the various TLB calls are mapped into corresponding Xen hypercalls. Control registers: all the control registers are privileged. The most important is cr3, which points to the base of the current pagetable, and we handle it specially. Another instruction we treat specially is CPUID, even though its not privileged. We want to control what CPU features are visible to the rest of the kernel, and so CPUID ends up going into a paravirt_op. Xen implements this mainly to disable the ACPI and APIC subsystems. INTERRUPT FLAGS Xen maintains its own separate flag for masking events, which is contained within the per-cpu vcpu_info structure. Because the guest kernel runs in ring 1 and not 0, the IF flag in EFLAGS is completely ignored (and must be, because even if a guest domain disables interrupts for itself, it can't disable them overall). (A note on terminology: "events" and interrupts are effectively synonymous. However, rather than using an "enable flag", Xen uses a "mask flag", which blocks event delivery when it is non-zero.) There are paravirt_ops for each of cli/sti/save_fl/restore_fl, which are implemented to manage the Xen event mask state. The only thing worth noting is that when events are unmasked, we need to explicitly see if there's a pending event and call into the hypervisor to make sure it gets delivered. UPCALLS Xen needs a couple of upcall (or callback) functions to be implemented by each guest. One is the event upcalls, which is how events (interrupts, effectively) are delivered to the guests. The other is the failsafe callback, which is used to report errors in either reloading a segment register, or caused by iret. These are implemented in i386/kernel/entry.S so they can jump into the normal iret_exc path when necessary. MULTICALL BATCHING Xen provides a multicall mechanism, which allows multiple hypercalls to be issued at once in order to mitigate the cost of trapping into the hypervisor. This is particularly useful for context switches, since the 4-5 hypercalls they would normally need (reload cr3, update TLS, maybe update LDT) can be reduced to one. This patch implements a generic batching mechanism for hypercalls, which gets used in many places in the Xen code. Signed-off-by: Jeremy Fitzhardinge Signed-off-by: Chris Wright Cc: Ian Pratt Cc: Christian Limpach Cc: Adrian Bunk

all-archs: consolidate .data section definition in asm-generic

2007-05-19T07:11:57+00:00

With this consolidation we can now modify the .data section definition in one spot for all archs. Signed-off-by: Sam Ravnborg

all-archs: consolidate .text section definition in asm-generic

2007-05-19T07:11:57+00:00

Move definition of .text section to asm-generic. Signed-off-by: Sam Ravnborg

Revert "[PATCH] paravirt: Add startup infrastructure for paravirtualization"

2007-05-10T16:26:53+00:00

This reverts commit c9ccf30d77f04064fe5436027ab9d2230c7cdd94. Entering the kernel at startup_32 without passing our real mode data in %esi, and without guaranteeing that physical and virtual addresses are identity mapped makes head.S impossible to maintain. The only user of this infrastructure is lguest which is not merged so nothing we currently support will break by removing this over designed nightmare, and only the pending lguest patches will be affected. The pending Xen patches have a different entry point that they use. We are currently discussing what Xen and lguest need to do to boot the kernel in a more normal fashion so using startup_32 in this weird manner is clearly not their long term direction. So let's remove this code in head.S before it causes brain damage to people trying to maintain head.S Cc: Chris Wright Cc: Andi Kleen Cc: Jeremy Fitzhardinge Cc: Zachary Amsden CC: H. Peter Anvin Signed-off-by: Eric W. Biederman Signed-off-by: Rusty Russell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] i386: Clean up ELF note generation

2007-05-02T17:27:17+00:00

Three cleanups: 1: ELF notes are never mapped, so there's no need to have any access flags in their phdr. 2: When generating them from asm, tell the assembler to use a SHT_NOTE section type. There doesn't seem to be a way to do this from C. 3: Use ANSI rather than traditional cpp behaviour to stringify the macro argument. Signed-off-by: Jeremy Fitzhardinge Signed-off-by: Andi Kleen Cc: Eric W. Biederman

[PATCH] x86: PARAVIRT: Jeremy Fitzhardinge

2007-05-02T17:27:16+00:00

The other symbols used to delineate the alt-instructions sections have the form __foo/__foo_end. Rename parainstructions to match. Signed-off-by: Jeremy Fitzhardinge Signed-off-by: Andi Kleen Cc: Andi Kleen Cc: Rusty Russell Signed-off-by: Andrew Morton