KVM: PPC: Implement MMU notifiers for Book3S HV guests

This adds the infrastructure to enable us to page out pages underneath
a Book3S HV guest, on processors that support virtualized partition
memory, that is, POWER7.  Instead of pinning all the guest's pages,
we now look in the host userspace Linux page tables to find the
mapping for a given guest page.  Then, if the userspace Linux PTE
gets invalidated, kvm_unmap_hva() gets called for that address, and
we replace all the guest HPTEs that refer to that page with absent
HPTEs, i.e. ones with the valid bit clear and the HPTE_V_ABSENT bit
set, which will cause an HDSI when the guest tries to access them.
Finally, the page fault handler is extended to reinstantiate the
guest HPTE when the guest tries to access a page which has been paged
out.

Since we can't intercept the guest DSI and ISI interrupts on PPC970,
we still have to pin all the guest pages on PPC970.  We have a new flag,
kvm->arch.using_mmu_notifiers, that indicates whether we can page
guest pages out.  If it is not set, the MMU notifier callbacks do
nothing and everything operates as before.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/powerpc/include/asm/kvm_book3s.h

@@ -143,6 +143,10 @@ extern void kvmppc_set_bat(struct kvm_vcpu *vcpu, struct kvmppc_bat *bat,
 extern void kvmppc_giveup_ext(struct kvm_vcpu *vcpu, ulong msr);
 extern int kvmppc_emulate_paired_single(struct kvm_run *run, struct kvm_vcpu *vcpu);
 extern pfn_t kvmppc_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn);
+extern void kvmppc_add_revmap_chain(struct kvm *kvm, struct revmap_entry *rev,
+			unsigned long *rmap, long pte_index, int realmode);
+extern void kvmppc_invalidate_hpte(struct kvm *kvm, unsigned long *hptep,
+			unsigned long pte_index);
 extern void *kvmppc_pin_guest_page(struct kvm *kvm, unsigned long addr,
 			unsigned long *nb_ret);
 extern void kvmppc_unpin_guest_page(struct kvm *kvm, void *addr);

arch/powerpc/include/asm/kvm_book3s_64.h

@@ -136,6 +136,37 @@ static inline int hpte_cache_flags_ok(unsigned long ptel, unsigned long io_type)
 	return (wimg & (HPTE_R_W | HPTE_R_I)) == io_type;
 }
 
+/*
+ * Lock and read a linux PTE.  If it's present and writable, atomically
+ * set dirty and referenced bits and return the PTE, otherwise return 0.
+ */
+static inline pte_t kvmppc_read_update_linux_pte(pte_t *p)
+{
+	pte_t pte, tmp;
+
+	/* wait until _PAGE_BUSY is clear then set it atomically */
+	__asm__ __volatile__ (
+		"1:	ldarx	%0,0,%3\n"
+		"	andi.	%1,%0,%4\n"
+		"	bne-	1b\n"
+		"	ori	%1,%0,%4\n"
+		"	stdcx.	%1,0,%3\n"
+		"	bne-	1b"
+		: "=&r" (pte), "=&r" (tmp), "=m" (*p)
+		: "r" (p), "i" (_PAGE_BUSY)
+		: "cc");
+
+	if (pte_present(pte)) {
+		pte = pte_mkyoung(pte);
+		if (pte_write(pte))
+			pte = pte_mkdirty(pte);
+	}
+
+	*p = pte;	/* clears _PAGE_BUSY */
+
+	return pte;
+}
+
 /* Return HPTE cache control bits corresponding to Linux pte bits */
 static inline unsigned long hpte_cache_bits(unsigned long pte_val)
 {

arch/powerpc/include/asm/kvm_host.h

@@ -32,6 +32,7 @@
 #include <linux/atomic.h>
 #include <asm/kvm_asm.h>
 #include <asm/processor.h>
+#include <asm/page.h>
 
 #define KVM_MAX_VCPUS		NR_CPUS
 #define KVM_MAX_VCORES		NR_CPUS
@@ -44,6 +45,19 @@
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
 #endif
 
+#ifdef CONFIG_KVM_BOOK3S_64_HV
+#include <linux/mmu_notifier.h>
+
+#define KVM_ARCH_WANT_MMU_NOTIFIER
+
+struct kvm;
+extern int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
+extern int kvm_age_hva(struct kvm *kvm, unsigned long hva);
+extern int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);
+extern void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);
+
+#endif
+
 /* We don't currently support large pages. */
 #define KVM_HPAGE_GFN_SHIFT(x)	0
 #define KVM_NR_PAGE_SIZES	1
@@ -212,6 +226,7 @@ struct kvm_arch {
 	struct kvmppc_rma_info *rma;
 	unsigned long vrma_slb_v;
 	int rma_setup_done;
+	int using_mmu_notifiers;
 	struct list_head spapr_tce_tables;
 	spinlock_t slot_phys_lock;
 	unsigned long *slot_phys[KVM_MEM_SLOTS_NUM];
@@ -460,6 +475,7 @@ struct kvm_vcpu_arch {
 	struct list_head run_list;
 	struct task_struct *run_task;
 	struct kvm_run *kvm_run;
+	pgd_t *pgdir;
 #endif
 };
 

arch/powerpc/include/asm/reg.h

@@ -495,6 +495,9 @@
 #define SPRN_SPRG7	0x117	/* Special Purpose Register General 7 */
 #define SPRN_SRR0	0x01A	/* Save/Restore Register 0 */
 #define SPRN_SRR1	0x01B	/* Save/Restore Register 1 */
+#define   SRR1_ISI_NOPT		0x40000000 /* ISI: Not found in hash */
+#define   SRR1_ISI_N_OR_G	0x10000000 /* ISI: Access is no-exec or G */
+#define   SRR1_ISI_PROT		0x08000000 /* ISI: Other protection fault */
 #define   SRR1_WAKEMASK		0x00380000 /* reason for wakeup */
 #define   SRR1_WAKESYSERR	0x00300000 /* System error */
 #define   SRR1_WAKEEE		0x00200000 /* External interrupt */

arch/powerpc/kvm/Kconfig

@@ -69,6 +69,7 @@ config KVM_BOOK3S_64
 config KVM_BOOK3S_64_HV
 	bool "KVM support for POWER7 and PPC970 using hypervisor mode in host"
 	depends on KVM_BOOK3S_64
+	select MMU_NOTIFIER
 	---help---
 	  Support running unmodified book3s_64 guest kernels in
 	  virtual machines on POWER7 and PPC970 processors that have