KVM: PPC: Book3S HV: Fix migration and HPT resizing of HPT guests on radix hosts

This fixes two errors that prevent a guest using the HPT MMU from
successfully migrating to a POWER9 host in radix MMU mode, or resizing
its HPT when running on a radix host.

The first bug was that commit 8dc6cca556e4 ("KVM: PPC: Book3S HV:
Don't rely on host's page size information", 2017-09-11) missed two
uses of hpte_base_page_size(), one in the HPT rehashing code and
one in kvm_htab_write() (which is used on the destination side in
migrating a HPT guest).  Instead we use kvmppc_hpte_base_page_shift().
Having the shift count means that we can use left and right shifts
instead of multiplication and division in a few places.

Along the way, this adds a check in kvm_htab_write() to ensure that the
page size encoding in the incoming HPTEs is recognized, and if not
return an EINVAL error to userspace.

The second bug was that kvm_htab_write was performing some but not all
of the functions of kvmhv_setup_mmu(), resulting in the destination VM
being left in radix mode as far as the hardware is concerned.  The
simplest fix for now is make kvm_htab_write() call
kvmppc_setup_partition_table() like kvmppc_hv_setup_htab_rma() does.
In future it would be better to refactor the code more extensively
to remove the duplication.

Fixes: 8dc6cca556e4 ("KVM: PPC: Book3S HV: Don't rely on host's page size information")
Fixes: 7a84084c6054 ("KVM: PPC: Book3S HV: Set partition table rather than SDR1 on POWER9")
Reported-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Tested-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

1 files changed, 23 insertions, 14 deletions

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 235319c2574e..966097232d21 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -1238,8 +1238,9 @@ static unsigned long resize_hpt_rehash_hpte(struct kvm_resize_hpt *resize,
 	unsigned long vpte, rpte, guest_rpte;
 	int ret;
 	struct revmap_entry *rev;
-	unsigned long apsize, psize, avpn, pteg, hash;
+	unsigned long apsize, avpn, pteg, hash;
 	unsigned long new_idx, new_pteg, replace_vpte;
+	int pshift;
 
 	hptep = (__be64 *)(old->virt + (idx << 4));
 
@@ -1298,8 +1299,8 @@ static unsigned long resize_hpt_rehash_hpte(struct kvm_resize_hpt *resize,
 		goto out;
 
 	rpte = be64_to_cpu(hptep[1]);
-	psize = hpte_base_page_size(vpte, rpte);
-	avpn = HPTE_V_AVPN_VAL(vpte) & ~((psize - 1) >> 23);
+	pshift = kvmppc_hpte_base_page_shift(vpte, rpte);
+	avpn = HPTE_V_AVPN_VAL(vpte) & ~(((1ul << pshift) - 1) >> 23);
 	pteg = idx / HPTES_PER_GROUP;
 	if (vpte & HPTE_V_SECONDARY)
 		pteg = ~pteg;
@@ -1311,20 +1312,20 @@ static unsigned long resize_hpt_rehash_hpte(struct kvm_resize_hpt *resize,
 		offset = (avpn & 0x1f) << 23;
 		vsid = avpn >> 5;
 		/* We can find more bits from the pteg value */
-		if (psize < (1ULL << 23))
-			offset |= ((vsid ^ pteg) & old_hash_mask) * psize;
+		if (pshift < 23)
+			offset |= ((vsid ^ pteg) & old_hash_mask) << pshift;
 
-		hash = vsid ^ (offset / psize);
+		hash = vsid ^ (offset >> pshift);
 	} else {
 		unsigned long offset, vsid;
 
 		/* We only have 40 - 23 bits of seg_off in avpn */
 		offset = (avpn & 0x1ffff) << 23;
 		vsid = avpn >> 17;
-		if (psize < (1ULL << 23))
-			offset |= ((vsid ^ (vsid << 25) ^ pteg) & old_hash_mask) * psize;
+		if (pshift < 23)
+			offset |= ((vsid ^ (vsid << 25) ^ pteg) & old_hash_mask) << pshift;
 
-		hash = vsid ^ (vsid << 25) ^ (offset / psize);
+		hash = vsid ^ (vsid << 25) ^ (offset >> pshift);
 	}
 
 	new_pteg = hash & new_hash_mask;
@@ -1801,6 +1802,7 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf,
 	ssize_t nb;
 	long int err, ret;
 	int mmu_ready;
+	int pshift;
 
 	if (!access_ok(VERIFY_READ, buf, count))
 		return -EFAULT;
@@ -1855,6 +1857,9 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf,
 			err = -EINVAL;
 			if (!(v & HPTE_V_VALID))
 				goto out;
+			pshift = kvmppc_hpte_base_page_shift(v, r);
+			if (pshift <= 0)
+				goto out;
 			lbuf += 2;
 			nb += HPTE_SIZE;
 
@@ -1869,14 +1874,18 @@ static ssize_t kvm_htab_write(struct file *file, const char __user *buf,
 				goto out;
 			}
 			if (!mmu_ready && is_vrma_hpte(v)) {
-				unsigned long psize = hpte_base_page_size(v, r);
-				unsigned long senc = slb_pgsize_encoding(psize);
-				unsigned long lpcr;
+				unsigned long senc, lpcr;
 
+				senc = slb_pgsize_encoding(1ul << pshift);
 				kvm->arch.vrma_slb_v = senc | SLB_VSID_B_1T |
 					(VRMA_VSID << SLB_VSID_SHIFT_1T);
-				lpcr = senc << (LPCR_VRMASD_SH - 4);
-				kvmppc_update_lpcr(kvm, lpcr, LPCR_VRMASD);
+				if (!cpu_has_feature(CPU_FTR_ARCH_300)) {
+					lpcr = senc << (LPCR_VRMASD_SH - 4);
+					kvmppc_update_lpcr(kvm, lpcr,
+							   LPCR_VRMASD);
+				} else {
+					kvmppc_setup_partition_table(kvm);
+				}
 				mmu_ready = 1;
 			}
 			++i;