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, 258 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
new file mode 100644
index 00000000000..4a4fbec61a1
--- /dev/null
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -0,0 +1,258 @@
+/*
+ * 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 2010 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
+ */
+
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/kvm.h>
+#include <linux/kvm_host.h>
+#include <linux/highmem.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+#include <linux/hugetlb.h>
+
+#include <asm/tlbflush.h>
+#include <asm/kvm_ppc.h>
+#include <asm/kvm_book3s.h>
+#include <asm/mmu-hash64.h>
+#include <asm/hvcall.h>
+#include <asm/synch.h>
+#include <asm/ppc-opcode.h>
+#include <asm/cputable.h>
+
+/* For now use fixed-size 16MB page table */
+#define HPT_ORDER	24
+#define HPT_NPTEG	(1ul << (HPT_ORDER - 7))	/* 128B per pteg */
+#define HPT_HASH_MASK	(HPT_NPTEG - 1)
+
+/* Pages in the VRMA are 16MB pages */
+#define VRMA_PAGE_ORDER	24
+#define VRMA_VSID	0x1ffffffUL	/* 1TB VSID reserved for VRMA */
+
+#define NR_LPIDS	(LPID_RSVD + 1)
+unsigned long lpid_inuse[BITS_TO_LONGS(NR_LPIDS)];
+
+long kvmppc_alloc_hpt(struct kvm *kvm)
+{
+	unsigned long hpt;
+	unsigned long lpid;
+
+	hpt = __get_free_pages(GFP_KERNEL|__GFP_ZERO|__GFP_REPEAT|__GFP_NOWARN,
+			       HPT_ORDER - PAGE_SHIFT);
+	if (!hpt) {
+		pr_err("kvm_alloc_hpt: Couldn't alloc HPT\n");
+		return -ENOMEM;
+	}
+	kvm->arch.hpt_virt = hpt;
+
+	do {
+		lpid = find_first_zero_bit(lpid_inuse, NR_LPIDS);
+		if (lpid >= NR_LPIDS) {
+			pr_err("kvm_alloc_hpt: No LPIDs free\n");
+			free_pages(hpt, HPT_ORDER - PAGE_SHIFT);
+			return -ENOMEM;
+		}
+	} while (test_and_set_bit(lpid, lpid_inuse));
+
+	kvm->arch.sdr1 = __pa(hpt) | (HPT_ORDER - 18);
+	kvm->arch.lpid = lpid;
+	kvm->arch.host_sdr1 = mfspr(SPRN_SDR1);
+	kvm->arch.host_lpid = mfspr(SPRN_LPID);
+	kvm->arch.host_lpcr = mfspr(SPRN_LPCR);
+
+	pr_info("KVM guest htab at %lx, LPID %lx\n", hpt, lpid);
+	return 0;
+}
+
+void kvmppc_free_hpt(struct kvm *kvm)
+{
+	unsigned long i;
+	struct kvmppc_pginfo *pginfo;
+
+	clear_bit(kvm->arch.lpid, lpid_inuse);
+	free_pages(kvm->arch.hpt_virt, HPT_ORDER - PAGE_SHIFT);
+
+	if (kvm->arch.ram_pginfo) {
+		pginfo = kvm->arch.ram_pginfo;
+		kvm->arch.ram_pginfo = NULL;
+		for (i = 0; i < kvm->arch.ram_npages; ++i)
+			put_page(pfn_to_page(pginfo[i].pfn));
+		kfree(pginfo);
+	}
+}
+
+static unsigned long user_page_size(unsigned long addr)
+{
+	struct vm_area_struct *vma;
+	unsigned long size = PAGE_SIZE;
+
+	down_read(&current->mm->mmap_sem);
+	vma = find_vma(current->mm, addr);
+	if (vma)
+		size = vma_kernel_pagesize(vma);
+	up_read(&current->mm->mmap_sem);
+	return size;
+}
+
+static pfn_t hva_to_pfn(unsigned long addr)
+{
+	struct page *page[1];
+	int npages;
+
+	might_sleep();
+
+	npages = get_user_pages_fast(addr, 1, 1, page);
+
+	if (unlikely(npages != 1))
+		return 0;
+
+	return page_to_pfn(page[0]);
+}
+
+long kvmppc_prepare_vrma(struct kvm *kvm,
+			 struct kvm_userspace_memory_region *mem)
+{
+	unsigned long psize, porder;
+	unsigned long i, npages;
+	struct kvmppc_pginfo *pginfo;
+	pfn_t pfn;
+	unsigned long hva;
+
+	/* First see what page size we have */
+	psize = user_page_size(mem->userspace_addr);
+	/* For now, only allow 16MB pages */
+	if (psize != 1ul << VRMA_PAGE_ORDER || (mem->memory_size & (psize - 1))) {
+		pr_err("bad psize=%lx memory_size=%llx @ %llx\n",
+		       psize, mem->memory_size, mem->userspace_addr);
+		return -EINVAL;
+	}
+	porder = __ilog2(psize);
+
+	npages = mem->memory_size >> porder;
+	pginfo = kzalloc(npages * sizeof(struct kvmppc_pginfo), GFP_KERNEL);
+	if (!pginfo) {
+		pr_err("kvmppc_prepare_vrma: couldn't alloc %lu bytes\n",
+		       npages * sizeof(struct kvmppc_pginfo));
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < npages; ++i) {
+		hva = mem->userspace_addr + (i << porder);
+		if (user_page_size(hva) != psize)
+			goto err;
+		pfn = hva_to_pfn(hva);
+		if (pfn == 0) {
+			pr_err("oops, no pfn for hva %lx\n", hva);
+			goto err;
+		}
+		if (pfn & ((1ul << (porder - PAGE_SHIFT)) - 1)) {
+			pr_err("oops, unaligned pfn %llx\n", pfn);
+			put_page(pfn_to_page(pfn));
+			goto err;
+		}
+		pginfo[i].pfn = pfn;
+	}
+
+	kvm->arch.ram_npages = npages;
+	kvm->arch.ram_psize = psize;
+	kvm->arch.ram_porder = porder;
+	kvm->arch.ram_pginfo = pginfo;
+
+	return 0;
+
+ err:
+	kfree(pginfo);
+	return -EINVAL;
+}
+
+void kvmppc_map_vrma(struct kvm *kvm, struct kvm_userspace_memory_region *mem)
+{
+	unsigned long i;
+	unsigned long npages = kvm->arch.ram_npages;
+	unsigned long pfn;
+	unsigned long *hpte;
+	unsigned long hash;
+	struct kvmppc_pginfo *pginfo = kvm->arch.ram_pginfo;
+
+	if (!pginfo)
+		return;
+
+	/* VRMA can't be > 1TB */
+	if (npages > 1ul << (40 - kvm->arch.ram_porder))
+		npages = 1ul << (40 - kvm->arch.ram_porder);
+	/* Can't use more than 1 HPTE per HPTEG */
+	if (npages > HPT_NPTEG)
+		npages = HPT_NPTEG;
+
+	for (i = 0; i < npages; ++i) {
+		pfn = pginfo[i].pfn;
+		/* can't use hpt_hash since va > 64 bits */
+		hash = (i ^ (VRMA_VSID ^ (VRMA_VSID << 25))) & HPT_HASH_MASK;
+		/*
+		 * We assume that the hash table is empty and no
+		 * vcpus are using it at this stage.  Since we create
+		 * at most one HPTE per HPTEG, we just assume entry 7
+		 * is available and use it.
+		 */
+		hpte = (unsigned long *) (kvm->arch.hpt_virt + (hash << 7));
+		hpte += 7 * 2;
+		/* HPTE low word - RPN, protection, etc. */
+		hpte[1] = (pfn << PAGE_SHIFT) | HPTE_R_R | HPTE_R_C |
+			HPTE_R_M | PP_RWXX;
+		wmb();
+		hpte[0] = HPTE_V_1TB_SEG | (VRMA_VSID << (40 - 16)) |
+			(i << (VRMA_PAGE_ORDER - 16)) | HPTE_V_BOLTED |
+			HPTE_V_LARGE | HPTE_V_VALID;
+	}
+}
+
+int kvmppc_mmu_hv_init(void)
+{
+	if (!cpu_has_feature(CPU_FTR_HVMODE_206))
+		return -EINVAL;
+	memset(lpid_inuse, 0, sizeof(lpid_inuse));
+	set_bit(mfspr(SPRN_LPID), lpid_inuse);
+	set_bit(LPID_RSVD, lpid_inuse);
+
+	return 0;
+}
+
+void kvmppc_mmu_destroy(struct kvm_vcpu *vcpu)
+{
+}
+
+static void kvmppc_mmu_book3s_64_hv_reset_msr(struct kvm_vcpu *vcpu)
+{
+	kvmppc_set_msr(vcpu, MSR_SF | MSR_ME);
+}
+
+static int kvmppc_mmu_book3s_64_hv_xlate(struct kvm_vcpu *vcpu, gva_t eaddr,
+				struct kvmppc_pte *gpte, bool data)
+{
+	return -ENOENT;
+}
+
+void kvmppc_mmu_book3s_hv_init(struct kvm_vcpu *vcpu)
+{
+	struct kvmppc_mmu *mmu = &vcpu->arch.mmu;
+
+	vcpu->arch.slb_nr = 32;		/* Assume POWER7 for now */
+
+	mmu->xlate = kvmppc_mmu_book3s_64_hv_xlate;
+	mmu->reset_msr = kvmppc_mmu_book3s_64_hv_reset_msr;
+
+	vcpu->arch.hflags |= BOOK3S_HFLAG_SLB;
+}