KVM: PPC: Add support for Book3S processors in hypervisor mode

This adds support for KVM running on 64-bit Book 3S processors,
specifically POWER7, in hypervisor mode.  Using hypervisor mode means
that the guest can use the processor's supervisor mode.  That means
that the guest can execute privileged instructions and access privileged
registers itself without trapping to the host.  This gives excellent
performance, but does mean that KVM cannot emulate a processor
architecture other than the one that the hardware implements.

This code assumes that the guest is running paravirtualized using the
PAPR (Power Architecture Platform Requirements) interface, which is the
interface that IBM's PowerVM hypervisor uses.  That means that existing
Linux distributions that run on IBM pSeries machines will also run
under KVM without modification.  In order to communicate the PAPR
hypercalls to qemu, this adds a new KVM_EXIT_PAPR_HCALL exit code
to include/linux/kvm.h.

Currently the choice between book3s_hv support and book3s_pr support
(i.e. the existing code, which runs the guest in user mode) has to be
made at kernel configuration time, so a given kernel binary can only
do one or the other.

This new book3s_hv code doesn't support MMIO emulation at present.
Since we are running paravirtualized guests, this isn't a serious
restriction.

With the guest running in supervisor mode, most exceptions go straight
to the guest.  We will never get data or instruction storage or segment
interrupts, alignment interrupts, decrementer interrupts, program
interrupts, single-step interrupts, etc., coming to the hypervisor from
the guest.  Therefore this introduces a new KVMTEST_NONHV macro for the
exception entry path so that we don't have to do the KVM test on entry
to those exception handlers.

We do however get hypervisor decrementer, hypervisor data storage,
hypervisor instruction storage, and hypervisor emulation assist
interrupts, so we have to handle those.

In hypervisor mode, real-mode accesses can access all of RAM, not just
a limited amount.  Therefore we put all the guest state in the vcpu.arch
and use the shadow_vcpu in the PACA only for temporary scratch space.
We allocate the vcpu with kzalloc rather than vzalloc, and we don't use
anything in the kvmppc_vcpu_book3s struct, so we don't allocate it.
We don't have a shared page with the guest, but we still need a
kvm_vcpu_arch_shared struct to store the values of various registers,
so we include one in the vcpu_arch struct.

The POWER7 processor has a restriction that all threads in a core have
to be in the same partition.  MMU-on kernel code counts as a partition
(partition 0), so we have to do a partition switch on every entry to and
exit from the guest.  At present we require the host and guest to run
in single-thread mode because of this hardware restriction.

This code allocates a hashed page table for the guest and initializes
it with HPTEs for the guest's Virtual Real Memory Area (VRMA).  We
require that the guest memory is allocated using 16MB huge pages, in
order to simplify the low-level memory management.  This also means that
we can get away without tracking paging activity in the host for now,
since huge pages can't be paged or swapped.

This also adds a few new exports needed by the book3s_hv code.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 35 insertions, 2 deletions

diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
index b7baff78f90c..5d9b78ebbaa6 100644
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig
@@ -20,7 +20,6 @@ config KVM
 	bool
 	select PREEMPT_NOTIFIERS
 	select ANON_INODES
-	select KVM_MMIO
 
 config KVM_BOOK3S_HANDLER
 	bool
@@ -28,16 +27,22 @@ config KVM_BOOK3S_HANDLER
 config KVM_BOOK3S_32_HANDLER
 	bool
 	select KVM_BOOK3S_HANDLER
+	select KVM_MMIO
 
 config KVM_BOOK3S_64_HANDLER
 	bool
 	select KVM_BOOK3S_HANDLER
 
+config KVM_BOOK3S_PR
+	bool
+	select KVM_MMIO
+
 config KVM_BOOK3S_32
 	tristate "KVM support for PowerPC book3s_32 processors"
 	depends on EXPERIMENTAL && PPC_BOOK3S_32 && !SMP && !PTE_64BIT
 	select KVM
 	select KVM_BOOK3S_32_HANDLER
+	select KVM_BOOK3S_PR
 	---help---
 	  Support running unmodified book3s_32 guest kernels
 	  in virtual machines on book3s_32 host processors.
@@ -50,8 +55,8 @@ config KVM_BOOK3S_32
 config KVM_BOOK3S_64
 	tristate "KVM support for PowerPC book3s_64 processors"
 	depends on EXPERIMENTAL && PPC_BOOK3S_64
-	select KVM
 	select KVM_BOOK3S_64_HANDLER
+	select KVM
 	---help---
 	  Support running unmodified book3s_64 and book3s_32 guest kernels
 	  in virtual machines on book3s_64 host processors.
@@ -61,10 +66,37 @@ config KVM_BOOK3S_64
 
 	  If unsure, say N.
 
+config KVM_BOOK3S_64_HV
+	bool "KVM support for POWER7 using hypervisor mode in host"
+	depends on KVM_BOOK3S_64
+	---help---
+	  Support running unmodified book3s_64 guest kernels in
+	  virtual machines on POWER7 processors that have hypervisor
+	  mode available to the host.
+
+	  If you say Y here, KVM will use the hardware virtualization
+	  facilities of POWER7 (and later) processors, meaning that
+	  guest operating systems will run at full hardware speed
+	  using supervisor and user modes.  However, this also means
+	  that KVM is not usable under PowerVM (pHyp), is only usable
+	  on POWER7 (or later) processors, and can only emulate
+	  POWER5+, POWER6 and POWER7 processors.
+
+	  This module provides access to the hardware capabilities through
+	  a character device node named /dev/kvm.
+
+	  If unsure, say N.
+
+config KVM_BOOK3S_64_PR
+	def_bool y
+	depends on KVM_BOOK3S_64 && !KVM_BOOK3S_64_HV
+	select KVM_BOOK3S_PR
+
 config KVM_440
 	bool "KVM support for PowerPC 440 processors"
 	depends on EXPERIMENTAL && 44x
 	select KVM
+	select KVM_MMIO
 	---help---
 	  Support running unmodified 440 guest kernels in virtual machines on
 	  440 host processors.
@@ -89,6 +121,7 @@ config KVM_E500
 	bool "KVM support for PowerPC E500 processors"
 	depends on EXPERIMENTAL && E500
 	select KVM
+	select KVM_MMIO
 	---help---
 	  Support running unmodified E500 guest kernels in virtual machines on
 	  E500 host processors.