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Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6
* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6: (25 commits) mmtimer: Push BKL down into the ioctl handler [IA64] Remove experimental status of kdump [IA64] Update ia64 mmr list for SGI uv [IA64] Avoid overflowing ia64_cpu_to_sapicid in acpi_map_lsapic() [IA64] adding parameter check to module_free() [IA64] improper printk format in acpi-cpufreq [IA64] pv_ops: move some functions in ivt.S to avoid lack of space. [IA64] pvops: documentation on ia64/pv_ops [IA64] pvops: add to hooks, pv_time_ops, for steal time accounting. [IA64] pvops: add hooks, pv_irq_ops, to paravirtualized irq related operations. [IA64] pvops: add hooks, pv_iosapic_ops, to paravirtualize iosapic. [IA64] pvops: define initialization hooks, pv_init_ops, for paravirtualized environment. [IA64] pvops: paravirtualize NR_IRQS [IA64] pvops: paravirtualize entry.S [IA64] pvops: paravirtualize ivt.S [IA64] pvops: paravirtualize minstate.h. [IA64] pvops: define paravirtualized instructions for native. [IA64] pvops: preparation for paravirtulization of hand written assembly code. [IA64] pvops: introduce pv_cpu_ops to paravirtualize privileged instructions. [IA64] pvops: add an early setup hook for pv_ops. ...
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‎Documentation/ia64/paravirt_ops.txt

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Paravirt_ops on IA64
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====================
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21 May 2008, Isaku Yamahata <yamahata@valinux.co.jp>
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Introduction
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------------
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The aim of this documentation is to help with maintainability and/or to
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encourage people to use paravirt_ops/IA64.
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paravirt_ops (pv_ops in short) is a way for virtualization support of
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Linux kernel on x86. Several ways for virtualization support were
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proposed, paravirt_ops is the winner.
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On the other hand, now there are also several IA64 virtualization
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technologies like kvm/IA64, xen/IA64 and many other academic IA64
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hypervisors so that it is good to add generic virtualization
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infrastructure on Linux/IA64.
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What is paravirt_ops?
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---------------------
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It has been developed on x86 as virtualization support via API, not ABI.
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It allows each hypervisor to override operations which are important for
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hypervisors at API level. And it allows a single kernel binary to run on
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all supported execution environments including native machine.
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Essentially paravirt_ops is a set of function pointers which represent
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operations corresponding to low level sensitive instructions and high
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level functionalities in various area. But one significant difference
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from usual function pointer table is that it allows optimization with
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binary patch. It is because some of these operations are very
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performance sensitive and indirect call overhead is not negligible.
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With binary patch, indirect C function call can be transformed into
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direct C function call or in-place execution to eliminate the overhead.
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Thus, operations of paravirt_ops are classified into three categories.
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- simple indirect call
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These operations correspond to high level functionality so that the
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overhead of indirect call isn't very important.
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- indirect call which allows optimization with binary patch
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Usually these operations correspond to low level instructions. They
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are called frequently and performance critical. So the overhead is
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very important.
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- a set of macros for hand written assembly code
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Hand written assembly codes (.S files) also need paravirtualization
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because they include sensitive instructions or some of code paths in
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them are very performance critical.
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The relation to the IA64 machine vector
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---------------------------------------
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Linux/IA64 has the IA64 machine vector functionality which allows the
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kernel to switch implementations (e.g. initialization, ipi, dma api...)
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depending on executing platform.
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We can replace some implementations very easily defining a new machine
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vector. Thus another approach for virtualization support would be
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enhancing the machine vector functionality.
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But paravirt_ops approach was taken because
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- virtualization support needs wider support than machine vector does.
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e.g. low level instruction paravirtualization. It must be
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initialized very early before platform detection.
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- virtualization support needs more functionality like binary patch.
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Probably the calling overhead might not be very large compared to the
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emulation overhead of virtualization. However in the native case, the
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overhead should be eliminated completely.
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A single kernel binary should run on each environment including native,
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and the overhead of paravirt_ops on native environment should be as
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small as possible.
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- for full virtualization technology, e.g. KVM/IA64 or
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Xen/IA64 HVM domain, the result would be
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(the emulated platform machine vector. probably dig) + (pv_ops).
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This means that the virtualization support layer should be under
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the machine vector layer.
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Possibly it might be better to move some function pointers from
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paravirt_ops to machine vector. In fact, Xen domU case utilizes both
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pv_ops and machine vector.
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IA64 paravirt_ops
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-----------------
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In this section, the concrete paravirt_ops will be discussed.
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Because of the architecture difference between ia64 and x86, the
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resulting set of functions is very different from x86 pv_ops.
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- C function pointer tables
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They are not very performance critical so that simple C indirect
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function call is acceptable. The following structures are defined at
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this moment. For details see linux/include/asm-ia64/paravirt.h
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- struct pv_info
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This structure describes the execution environment.
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- struct pv_init_ops
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This structure describes the various initialization hooks.
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- struct pv_iosapic_ops
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This structure describes hooks to iosapic operations.
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- struct pv_irq_ops
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This structure describes hooks to irq related operations
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- struct pv_time_op
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This structure describes hooks to steal time accounting.
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- a set of indirect calls which need optimization
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Currently this class of functions correspond to a subset of IA64
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intrinsics. At this moment the optimization with binary patch isn't
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implemented yet.
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struct pv_cpu_op is defined. For details see
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linux/include/asm-ia64/paravirt_privop.h
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Mostly they correspond to ia64 intrinsics 1-to-1.
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Caveat: Now they are defined as C indirect function pointers, but in
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order to support binary patch optimization, they will be changed
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using GCC extended inline assembly code.
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- a set of macros for hand written assembly code (.S files)
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For maintenance purpose, the taken approach for .S files is single
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source code and compile multiple times with different macros definitions.
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Each pv_ops instance must define those macros to compile.
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The important thing here is that sensitive, but non-privileged
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instructions must be paravirtualized and that some privileged
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instructions also need paravirtualization for reasonable performance.
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Developers who modify .S files must be aware of that. At this moment
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an easy checker is implemented to detect paravirtualization breakage.
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But it doesn't cover all the cases.
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Sometimes this set of macros is called pv_cpu_asm_op. But there is no
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corresponding structure in the source code.
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Those macros mostly 1:1 correspond to a subset of privileged
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instructions. See linux/include/asm-ia64/native/inst.h.
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And some functions written in assembly also need to be overrided so
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that each pv_ops instance have to define some macros. Again see
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linux/include/asm-ia64/native/inst.h.
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Those structures must be initialized very early before start_kernel.
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Probably initialized in head.S using multi entry point or some other trick.
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For native case implementation see linux/arch/ia64/kernel/paravirt.c.

‎arch/ia64/Kconfig

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strongly in flux, so no good recommendation can be made.
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config CRASH_DUMP
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bool "kernel crash dumps (EXPERIMENTAL)"
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depends on EXPERIMENTAL && IA64_MCA_RECOVERY && !IA64_HP_SIM && (!SMP || HOTPLUG_CPU)
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bool "kernel crash dumps"
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depends on IA64_MCA_RECOVERY && !IA64_HP_SIM && (!SMP || HOTPLUG_CPU)
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help
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Generate crash dump after being started by kexec.
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‎arch/ia64/Makefile

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echo ' boot - Build vmlinux and bootloader for Ski simulator'
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echo '* unwcheck - Check vmlinux for invalid unwind info'
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endef
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archprepare: make_nr_irqs_h FORCE
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PHONY += make_nr_irqs_h FORCE
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make_nr_irqs_h: FORCE
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$(Q)$(MAKE) $(build)=arch/ia64/kernel include/asm-ia64/nr-irqs.h

‎arch/ia64/kernel/Makefile

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mca_recovery-y += mca_drv.o mca_drv_asm.o
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obj-$(CONFIG_IA64_MC_ERR_INJECT)+= err_inject.o
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obj-$(CONFIG_PARAVIRT) += paravirt.o paravirtentry.o
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obj-$(CONFIG_IA64_ESI) += esi.o
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ifneq ($(CONFIG_IA64_ESI),)
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obj-y += esi_stub.o # must be in kernel proper
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# We must build gate.so before we can assemble it.
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# Note: kbuild does not track this dependency due to usage of .incbin
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$(obj)/gate-data.o: $(obj)/gate.so
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# Calculate NR_IRQ = max(IA64_NATIVE_NR_IRQS, XEN_NR_IRQS, ...) based on config
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define sed-y
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"/^->/{s:^->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; s:->::; p;}"
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endef
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quiet_cmd_nr_irqs = GEN $@
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define cmd_nr_irqs
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(set -e; \
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echo "#ifndef __ASM_NR_IRQS_H__"; \
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echo "#define __ASM_NR_IRQS_H__"; \
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echo "/*"; \
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echo " * DO NOT MODIFY."; \
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echo " *"; \
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echo " * This file was generated by Kbuild"; \
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echo " *"; \
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echo " */"; \
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echo ""; \
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sed -ne $(sed-y) $<; \
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echo ""; \
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echo "#endif" ) > $@
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endef
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# We use internal kbuild rules to avoid the "is up to date" message from make
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arch/$(SRCARCH)/kernel/nr-irqs.s: $(srctree)/arch/$(SRCARCH)/kernel/nr-irqs.c \
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$(wildcard $(srctree)/include/asm-ia64/*/irq.h)
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$(Q)mkdir -p $(dir $@)
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$(call if_changed_dep,cc_s_c)
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include/asm-ia64/nr-irqs.h: arch/$(SRCARCH)/kernel/nr-irqs.s
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$(Q)mkdir -p $(dir $@)
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$(call cmd,nr_irqs)
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clean-files += $(objtree)/include/asm-ia64/nr-irqs.h
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#
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# native ivt.S and entry.S
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#
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ASM_PARAVIRT_OBJS = ivt.o entry.o
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define paravirtualized_native
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AFLAGS_$(1) += -D__IA64_ASM_PARAVIRTUALIZED_NATIVE
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endef
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$(foreach obj,$(ASM_PARAVIRT_OBJS),$(eval $(call paravirtualized_native,$(obj))))

‎arch/ia64/kernel/acpi.c

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*/
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#ifdef CONFIG_ACPI_HOTPLUG_CPU
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static
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int acpi_map_cpu2node(acpi_handle handle, int cpu, long physid)
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int acpi_map_cpu2node(acpi_handle handle, int cpu, int physid)
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{
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#ifdef CONFIG_ACPI_NUMA
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int pxm_id;
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union acpi_object *obj;
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struct acpi_madt_local_sapic *lsapic;
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cpumask_t tmp_map;
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long physid;
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int cpu;
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int cpu, physid;
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if (ACPI_FAILURE(acpi_evaluate_object(handle, "_MAT", NULL, &buffer)))
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return -EINVAL;

‎arch/ia64/kernel/cpufreq/acpi-cpufreq.c

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retval = ia64_pal_set_pstate((u64)value);
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if (retval) {
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dprintk("Failed to set freq to 0x%x, with error 0x%x\n",
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dprintk("Failed to set freq to 0x%x, with error 0x%lx\n",
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value, retval);
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return -ENODEV;
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}
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if (retval)
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dprintk("Failed to get current freq with "
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"error 0x%x, idx 0x%x\n", retval, *value);
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"error 0x%lx, idx 0x%x\n", retval, *value);
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return (int)retval;
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}

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