KVM: PPC: Book3S HV: Restructure HPT entry creation code

This restructures the code that creates HPT (hashed page table)
entries so that it can be called in situations where we don't have a
struct vcpu pointer, only a struct kvm pointer.  It also fixes a bug
where kvmppc_map_vrma() would corrupt the guest R4 value.

Most of the work of kvmppc_virtmode_h_enter is now done by a new
function, kvmppc_virtmode_do_h_enter, which itself calls another new
function, kvmppc_do_h_enter, which contains most of the old
kvmppc_h_enter.  The new kvmppc_do_h_enter takes explicit arguments
for the place to return the HPTE index, the Linux page tables to use,
and whether it is being called in real mode, thus removing the need
for it to have the vcpu as an argument.

Currently kvmppc_map_vrma creates the VRMA (virtual real mode area)
HPTEs by calling kvmppc_virtmode_h_enter, which is designed primarily
to handle H_ENTER hcalls from the guest that need to pin a page of
memory.  Since H_ENTER returns the index of the created HPTE in R4,
kvmppc_virtmode_h_enter updates the guest R4, corrupting the guest R4
in the case when it gets called from kvmppc_map_vrma on the first
VCPU_RUN ioctl.  With this, kvmppc_map_vrma instead calls
kvmppc_virtmode_do_h_enter with the address of a dummy word as the
place to store the HPTE index, thus avoiding corrupting the guest R4.

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

1 files changed, 25 insertions, 11 deletions

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 2a89a36e7263..6ee6516a0bee 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -41,6 +41,10 @@
 /* Power architecture requires HPT is at least 256kB */
 #define PPC_MIN_HPT_ORDER	18
 
+static long kvmppc_virtmode_do_h_enter(struct kvm *kvm, unsigned long flags,
+				long pte_index, unsigned long pteh,
+				unsigned long ptel, unsigned long *pte_idx_ret);
+
 long kvmppc_alloc_hpt(struct kvm *kvm, u32 *htab_orderp)
 {
 	unsigned long hpt;
@@ -185,6 +189,7 @@ void kvmppc_map_vrma(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
 	unsigned long addr, hash;
 	unsigned long psize;
 	unsigned long hp0, hp1;
+	unsigned long idx_ret;
 	long ret;
 	struct kvm *kvm = vcpu->kvm;
 
@@ -216,7 +221,8 @@ void kvmppc_map_vrma(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
 		hash = (hash << 3) + 7;
 		hp_v = hp0 | ((addr >> 16) & ~0x7fUL);
 		hp_r = hp1 | addr;
-		ret = kvmppc_virtmode_h_enter(vcpu, H_EXACT, hash, hp_v, hp_r);
+		ret = kvmppc_virtmode_do_h_enter(kvm, H_EXACT, hash, hp_v, hp_r,
+						 &idx_ret);
 		if (ret != H_SUCCESS) {
 			pr_err("KVM: map_vrma at %lx failed, ret=%ld\n",
 			       addr, ret);
@@ -354,15 +360,10 @@ static long kvmppc_get_guest_page(struct kvm *kvm, unsigned long gfn,
 	return err;
 }
 
-/*
- * We come here on a H_ENTER call from the guest when we are not
- * using mmu notifiers and we don't have the requested page pinned
- * already.
- */
-long kvmppc_virtmode_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
-			long pte_index, unsigned long pteh, unsigned long ptel)
+long kvmppc_virtmode_do_h_enter(struct kvm *kvm, unsigned long flags,
+				long pte_index, unsigned long pteh,
+				unsigned long ptel, unsigned long *pte_idx_ret)
 {
-	struct kvm *kvm = vcpu->kvm;
 	unsigned long psize, gpa, gfn;
 	struct kvm_memory_slot *memslot;
 	long ret;
@@ -390,8 +391,8 @@ long kvmppc_virtmode_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
  do_insert:
 	/* Protect linux PTE lookup from page table destruction */
 	rcu_read_lock_sched();	/* this disables preemption too */
-	vcpu->arch.pgdir = current->mm->pgd;
-	ret = kvmppc_h_enter(vcpu, flags, pte_index, pteh, ptel);
+	ret = kvmppc_do_h_enter(kvm, flags, pte_index, pteh, ptel,
+				current->mm->pgd, false, pte_idx_ret);
 	rcu_read_unlock_sched();
 	if (ret == H_TOO_HARD) {
 		/* this can't happen */
@@ -402,6 +403,19 @@ long kvmppc_virtmode_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
 
 }
 
+/*
+ * We come here on a H_ENTER call from the guest when we are not
+ * using mmu notifiers and we don't have the requested page pinned
+ * already.
+ */
+long kvmppc_virtmode_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
+			     long pte_index, unsigned long pteh,
+			     unsigned long ptel)
+{
+	return kvmppc_virtmode_do_h_enter(vcpu->kvm, flags, pte_index,
+					  pteh, ptel, &vcpu->arch.gpr[4]);
+}
+
 static struct kvmppc_slb *kvmppc_mmu_book3s_hv_find_slbe(struct kvm_vcpu *vcpu,
 							 gva_t eaddr)
 {