KVM: PPC: Book3S HV: Make the guest hash table size configurable

This adds a new ioctl to enable userspace to control the size of the guest
hashed page table (HPT) and to clear it out when resetting the guest.
The KVM_PPC_ALLOCATE_HTAB ioctl is a VM ioctl and takes as its parameter
a pointer to a u32 containing the desired order of the HPT (log base 2
of the size in bytes), which is updated on successful return to the
actual order of the HPT which was allocated.

There must be no vcpus running at the time of this ioctl.  To enforce
this, we now keep a count of the number of vcpus running in
kvm->arch.vcpus_running.

If the ioctl is called when a HPT has already been allocated, we don't
reallocate the HPT but just clear it out.  We first clear the
kvm->arch.rma_setup_done flag, which has two effects: (a) since we hold
the kvm->lock mutex, it will prevent any vcpus from starting to run until
we're done, and (b) it means that the first vcpu to run after we're done
will re-establish the VRMA if necessary.

If userspace doesn't call this ioctl before running the first vcpu, the
kernel will allocate a default-sized HPT at that point.  We do it then
rather than when creating the VM, as the code did previously, so that
userspace has a chance to do the ioctl if it wants.

When allocating the HPT, we can allocate either from the kernel page
allocator, or from the preallocated pool.  If userspace is asking for
a different size from the preallocated HPTs, we first try to allocate
using the kernel page allocator.  Then we try to allocate from the
preallocated pool, and then if that fails, we try allocating decreasing
sizes from the kernel page allocator, down to the minimum size allowed
(256kB).  Note that the kernel page allocator limits allocations to
1 << CONFIG_FORCE_MAX_ZONEORDER pages, which by default corresponds to
16MB (on 64-bit powerpc, at least).

Signed-off-by: Paul Mackerras <paulus@samba.org>
[agraf: fix module compilation]
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 28 insertions, 12 deletions

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index c6af1d62383..d084e412b3c 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -56,7 +56,7 @@
 /* #define EXIT_DEBUG_INT */
 
 static void kvmppc_end_cede(struct kvm_vcpu *vcpu);
-static int kvmppc_hv_setup_rma(struct kvm_vcpu *vcpu);
+static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu);
 
 void kvmppc_core_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
@@ -1068,11 +1068,15 @@ int kvmppc_vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu)
 		return -EINTR;
 	}
 
-	/* On the first time here, set up VRMA or RMA */
+	atomic_inc(&vcpu->kvm->arch.vcpus_running);
+	/* Order vcpus_running vs. rma_setup_done, see kvmppc_alloc_reset_hpt */
+	smp_mb();
+
+	/* On the first time here, set up HTAB and VRMA or RMA */
 	if (!vcpu->kvm->arch.rma_setup_done) {
-		r = kvmppc_hv_setup_rma(vcpu);
+		r = kvmppc_hv_setup_htab_rma(vcpu);
 		if (r)
-			return r;
+			goto out;
 	}
 
 	flush_fp_to_thread(current);
@@ -1090,6 +1094,9 @@ int kvmppc_vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu)
 			kvmppc_core_prepare_to_enter(vcpu);
 		}
 	} while (r == RESUME_GUEST);
+
+ out:
+	atomic_dec(&vcpu->kvm->arch.vcpus_running);
 	return r;
 }
 
@@ -1305,7 +1312,7 @@ void kvmppc_core_commit_memory_region(struct kvm *kvm,
 {
 }
 
-static int kvmppc_hv_setup_rma(struct kvm_vcpu *vcpu)
+static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu)
 {
 	int err = 0;
 	struct kvm *kvm = vcpu->kvm;
@@ -1324,6 +1331,15 @@ static int kvmppc_hv_setup_rma(struct kvm_vcpu *vcpu)
 	if (kvm->arch.rma_setup_done)
 		goto out;	/* another vcpu beat us to it */
 
+	/* Allocate hashed page table (if not done already) and reset it */
+	if (!kvm->arch.hpt_virt) {
+		err = kvmppc_alloc_hpt(kvm, NULL);
+		if (err) {
+			pr_err("KVM: Couldn't alloc HPT\n");
+			goto out;
+		}
+	}
+
 	/* Look up the memslot for guest physical address 0 */
 	memslot = gfn_to_memslot(kvm, 0);
 
@@ -1435,13 +1451,14 @@ static int kvmppc_hv_setup_rma(struct kvm_vcpu *vcpu)
 
 int kvmppc_core_init_vm(struct kvm *kvm)
 {
-	long r;
-	unsigned long lpcr;
+	unsigned long lpcr, lpid;
 
-	/* Allocate hashed page table */
-	r = kvmppc_alloc_hpt(kvm);
-	if (r)
-		return r;
+	/* Allocate the guest's logical partition ID */
+
+	lpid = kvmppc_alloc_lpid();
+	if (lpid < 0)
+		return -ENOMEM;
+	kvm->arch.lpid = lpid;
 
 	INIT_LIST_HEAD(&kvm->arch.spapr_tce_tables);
 
@@ -1451,7 +1468,6 @@ int kvmppc_core_init_vm(struct kvm *kvm)
 
 	if (cpu_has_feature(CPU_FTR_ARCH_201)) {
 		/* PPC970; HID4 is effectively the LPCR */
-		unsigned long lpid = kvm->arch.lpid;
 		kvm->arch.host_lpid = 0;
 		kvm->arch.host_lpcr = lpcr = mfspr(SPRN_HID4);
 		lpcr &= ~((3 << HID4_LPID1_SH) | (0xful << HID4_LPID5_SH));