KVM: PPC: Remove 440 support

	- Documentation on the firmware assisted dump mechanism "fadump".

hvcs.txt

	- IBM "Hypervisor Virtual Console Server" Installation Guide

kvm_440.txt

	- Various notes on the implementation of KVM for PowerPC 440.

mpc52xx.txt

	- Linux 2.6.x on MPC52xx family

pmu-ebb.txt

Hollis Blanchard <hollisb@us.ibm.com>

15 Apr 2008

Various notes on the implementation of KVM for PowerPC 440:

To enforce isolation, host userspace, guest kernel, and guest userspace all

run at user privilege level. Only the host kernel runs in supervisor mode.

Executing privileged instructions in the guest traps into KVM (in the host

kernel), where we decode and emulate them. Through this technique, unmodified

440 Linux kernels can be run (slowly) as guests. Future performance work will

focus on reducing the overhead and frequency of these traps.

The usual code flow is started from userspace invoking an "run" ioctl, which

causes KVM to switch into guest context. We use IVPR to hijack the host

interrupt vectors while running the guest, which allows us to direct all

interrupts to kvmppc_handle_interrupt(). At this point, we could either

- handle the interrupt completely (e.g. emulate "mtspr SPRG0"), or

- let the host interrupt handler run (e.g. when the decrementer fires), or

- return to host userspace (e.g. when the guest performs device MMIO)

Address spaces: We take advantage of the fact that Linux doesn't use the AS=1

address space (in host or guest), which gives us virtual address space to use

for guest mappings. While the guest is running, the host kernel remains mapped

in AS=0, but the guest can only use AS=1 mappings.

TLB entries: The TLB entries covering the host linear mapping remain

present while running the guest. This reduces the overhead of lightweight

exits, which are handled by KVM running in the host kernel. We keep three

copies of the TLB:

 - guest TLB: contents of the TLB as the guest sees it

 - shadow TLB: the TLB that is actually in hardware while guest is running

 - host TLB: to restore TLB state when context switching guest -> host

When a TLB miss occurs because a mapping was not present in the shadow TLB,

but was present in the guest TLB, KVM handles the fault without invoking the

guest. Large guest pages are backed by multiple 4KB shadow pages through this

mechanism.

IO: MMIO and DCR accesses are emulated by userspace. We use virtio for network

and block IO, so those drivers must be enabled in the guest. It's possible

that some qemu device emulation (e.g. e1000 or rtl8139) may also work with

little effort.

config PPC_EARLY_DEBUG_44x

	bool "Early serial debugging for IBM/AMCC 44x CPUs"

	# PPC_EARLY_DEBUG on 440 leaves AS=1 mappings above the TLB high water

	# mark, which doesn't work with current 440 KVM.

	depends on 44x && !KVM

	depends on 44x

	help

	  Select this to enable early debugging for IBM 44x chips via the

	  inbuilt serial port.  If you enable this, ensure you set

# CONFIG_CRYPTO_ANSI_CPRNG is not set

# CONFIG_CRYPTO_HW is not set

CONFIG_VIRTUALIZATION=y

CONFIG_KVM_440=y

/*

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License, version 2, as

 * published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

 *

 * Copyright IBM Corp. 2008

 *

 * Authors: Hollis Blanchard <hollisb@us.ibm.com>

 */

#ifndef __ASM_44X_H__

#define __ASM_44X_H__

#include <linux/kvm_host.h>

#define PPC44x_TLB_SIZE 64

/* If the guest is expecting it, this can be as large as we like; we'd just

 * need to find some way of advertising it. */

#define KVM44x_GUEST_TLB_SIZE 64

struct kvmppc_44x_tlbe {

	u32 tid; /* Only the low 8 bits are used. */

	u32 word0;

	u32 word1;

	u32 word2;

};

struct kvmppc_44x_shadow_ref {

	struct page *page;

	u16 gtlb_index;

	u8 writeable;

	u8 tid;

};

struct kvmppc_vcpu_44x {

	/* Unmodified copy of the guest's TLB. */

	struct kvmppc_44x_tlbe guest_tlb[KVM44x_GUEST_TLB_SIZE];

	/* References to guest pages in the hardware TLB. */

	struct kvmppc_44x_shadow_ref shadow_refs[PPC44x_TLB_SIZE];

	/* State of the shadow TLB at guest context switch time. */

	struct kvmppc_44x_tlbe shadow_tlb[PPC44x_TLB_SIZE];

	u8 shadow_tlb_mod[PPC44x_TLB_SIZE];

	struct kvm_vcpu vcpu;

};

static inline struct kvmppc_vcpu_44x *to_44x(struct kvm_vcpu *vcpu)

{

	return container_of(vcpu, struct kvmppc_vcpu_44x, vcpu);

}

void kvmppc_44x_tlb_put(struct kvm_vcpu *vcpu);

void kvmppc_44x_tlb_load(struct kvm_vcpu *vcpu);

#endif /* __ASM_44X_H__ */