KVM: PPC: Book3S HV: Flush guest mappings when turning dirty tracking on/off

This adds code to flush the partition-scoped page tables for a radix
guest when dirty tracking is turned on or off for a memslot.  Only the
guest real addresses covered by the memslot are flushed.  The reason
for this is to get rid of any 2M PTEs in the partition-scoped page
tables that correspond to host transparent huge pages, so that page
dirtiness is tracked at a system page (4k or 64k) granularity rather
than a 2M granularity.  The page tables are also flushed when turning
dirty tracking off so that the memslot's address space can be
repopulated with THPs if possible.

To do this, we add a new function kvmppc_radix_flush_memslot().  Since
this does what's needed for kvmppc_core_flush_memslot_hv() on a radix
guest, we now make kvmppc_core_flush_memslot_hv() call the new
kvmppc_radix_flush_memslot() rather than calling kvm_unmap_radix()
for each page in the memslot.  This has the effect of fixing a bug in
that kvmppc_core_flush_memslot_hv() was previously calling
kvm_unmap_radix() without holding the kvm->mmu_lock spinlock, which
is required to be held.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index 52711eb052f5..d675ad92c7ad 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -958,6 +958,26 @@ long kvmppc_hv_get_dirty_log_radix(struct kvm *kvm,
 	return 0;
 }
 
+void kvmppc_radix_flush_memslot(struct kvm *kvm,
+				const struct kvm_memory_slot *memslot)
+{
+	unsigned long n;
+	pte_t *ptep;
+	unsigned long gpa;
+	unsigned int shift;
+
+	gpa = memslot->base_gfn << PAGE_SHIFT;
+	spin_lock(&kvm->mmu_lock);
+	for (n = memslot->npages; n; --n) {
+		ptep = __find_linux_pte(kvm->arch.pgtable, gpa, NULL, &shift);
+		if (ptep && pte_present(*ptep))
+			kvmppc_unmap_pte(kvm, ptep, gpa, shift, memslot,
+					 kvm->arch.lpid);
+		gpa += PAGE_SIZE;
+	}
+	spin_unlock(&kvm->mmu_lock);
+}
+
 static void add_rmmu_ap_encoding(struct kvm_ppc_rmmu_info *info,
 				 int psize, int *indexp)
 {