KVM: PPC: Book3S PR: Correct errors in H_ENTER implementation

The implementation of H_ENTER in PR KVM has some errors:

* With H_EXACT not set, if the HPTEG is full, we return H_PTEG_FULL
  as the return value of kvmppc_h_pr_enter, but the caller is expecting
  one of the EMULATE_* values.  The H_PTEG_FULL needs to go in the
  guest's R3 instead.

* With H_EXACT set, if the selected HPTE is already valid, the H_ENTER
  call should return a H_PTEG_FULL error.

This fixes these errors and also makes it write only the selected HPTE,
not the whole group, since only the selected HPTE has been modified.
This also micro-optimizes the calculations involving pte_index and i.

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

diff --git a/arch/powerpc/kvm/book3s_pr_papr.c b/arch/powerpc/kvm/book3s_pr_papr.c
index da0e0bc..38f1899 100644 (file)
--- a/arch/powerpc/kvm/book3s_pr_papr.c
+++ b/arch/powerpc/kvm/book3s_pr_papr.c
@@ -21,6 +21,8 @@
 #include <asm/kvm_ppc.h>
 #include <asm/kvm_book3s.h>
 
+#define HPTE_SIZE      16              /* bytes per HPT entry */
+
 static unsigned long get_pteg_addr(struct kvm_vcpu *vcpu, long pte_index)
 {
        struct kvmppc_vcpu_book3s *vcpu_book3s = to_book3s(vcpu);
@@ -40,32 +42,39 @@ static int kvmppc_h_pr_enter(struct kvm_vcpu *vcpu)
        long pte_index = kvmppc_get_gpr(vcpu, 5);
        unsigned long pteg[2 * 8];
        unsigned long pteg_addr, i, *hpte;
+       long int ret;
 
+       i = pte_index & 7;
        pte_index &= ~7UL;
        pteg_addr = get_pteg_addr(vcpu, pte_index);
 
        copy_from_user(pteg, (void __user *)pteg_addr, sizeof(pteg));
        hpte = pteg;
 
+       ret = H_PTEG_FULL;
        if (likely((flags & H_EXACT) == 0)) {
-               pte_index &= ~7UL;
                for (i = 0; ; ++i) {
                        if (i == 8)
-                               return H_PTEG_FULL;
+                               goto done;
                        if ((*hpte & HPTE_V_VALID) == 0)
                                break;
                        hpte += 2;
                }
        } else {
-               i = kvmppc_get_gpr(vcpu, 5) & 7UL;
                hpte += i * 2;
+               if (*hpte & HPTE_V_VALID)
+                       goto done;
        }
 
        hpte[0] = kvmppc_get_gpr(vcpu, 6);
        hpte[1] = kvmppc_get_gpr(vcpu, 7);
-       copy_to_user((void __user *)pteg_addr, pteg, sizeof(pteg));
-       kvmppc_set_gpr(vcpu, 3, H_SUCCESS);
+       pteg_addr += i * HPTE_SIZE;
+       copy_to_user((void __user *)pteg_addr, hpte, HPTE_SIZE);
        kvmppc_set_gpr(vcpu, 4, pte_index | i);
+       ret = H_SUCCESS;
+
+ done:
+       kvmppc_set_gpr(vcpu, 3, ret);
 
        return EMULATE_DONE;
 }