[PATCH 4/4] KVM: s390: Replace get_zeroed_page() with kzalloc() for sie_page2 and CMMA

[Mike Rapoport (Microsoft)]

kvm_arch_init_vm() allocates struct sie_page2 that holds the facility
list and the crypto control block of a VM and kvm_s390_vcpu_setup_cmma()
allocates the CMMA collaborative memory management block referenced by
the SIE control block. Both are passed to the hardware as physical
addresses and must be page aligned.

kmalloc() guarantees that a power of two sized allocation is aligned to
its size, so a PAGE_SIZE allocation is page aligned as well.

These buffers can be allocated with kmalloc() as there's nothing special
about them to go directly to the page allocator.

kmalloc() provides a better API that does not require ugly casts and
kfree() does not need to know the size of the freed object.

Performance difference between kmalloc() and __get_free_pages() is not
measurable as both allocators take an object/page from a per-CPU list for
fast path allocations.

For the slow path the performance is anyway determined by the amount of
reclaim involved rather than by what allocator is used.

The sie_page allocated in kvm_arch_vcpu_create() is left alone because it
is mapped to userspace with virt_to_page() in kvm_arch_vcpu_fault() and
therefore really needs a struct page.

Replace use of get_zeroed_page() with kzalloc() and free_page() with
kfree().

Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@xxxxxxxxxx
Assisted-by: copilot:claude-opus
Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
---
 arch/s390/kvm/s390/s390.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/s390/kvm/s390/s390.c b/arch/s390/kvm/s390/s390.c
index b0839e887221e..8ec505060f8c0 100644
--- a/arch/s390/kvm/s390/s390.c
+++ b/arch/s390/kvm/s390/s390.c
@@ -3273,8 +3273,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 		goto out_err;
 
 	BUILD_BUG_ON(sizeof(struct sie_page2) != 4096);
-	kvm->arch.sie_page2 =
-	     (struct sie_page2 *) get_zeroed_page(GFP_KERNEL_ACCOUNT | GFP_DMA);
+	kvm->arch.sie_page2 = kzalloc_obj(*kvm->arch.sie_page2,
+					  GFP_KERNEL_ACCOUNT | GFP_DMA);
 	if (!kvm->arch.sie_page2)
 		goto out_err;
 
@@ -3369,7 +3369,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 
 	return 0;
 out_err:
-	free_page((unsigned long)kvm->arch.sie_page2);
+	kfree(kvm->arch.sie_page2);
 	debug_unregister(kvm->arch.dbf);
 	sca_dispose(kvm);
 	KVM_EVENT(3, "creation of vm failed: %d", rc);
@@ -3427,7 +3427,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
 		mmu_notifier_unregister(&kvm->arch.pv.mmu_notifier, kvm->mm);
 
 	debug_unregister(kvm->arch.dbf);
-	free_page((unsigned long)kvm->arch.sie_page2);
+	kfree(kvm->arch.sie_page2);
 	kvm_s390_destroy_adapters(kvm);
 	kvm_s390_clear_float_irqs(kvm);
 	kvm_s390_vsie_destroy(kvm);
@@ -3657,13 +3657,13 @@ static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu)
 void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu)
 {
 	if (vcpu->arch.sie_block->cbrlo)
-		free_page((unsigned long)phys_to_virt(vcpu->arch.sie_block->cbrlo));
+		kfree(phys_to_virt(vcpu->arch.sie_block->cbrlo));
 	vcpu->arch.sie_block->cbrlo = 0;
 }
 
 int kvm_s390_vcpu_setup_cmma(struct kvm_vcpu *vcpu)
 {
-	void *cbrlo_page = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
+	void *cbrlo_page = kzalloc(PAGE_SIZE, GFP_KERNEL_ACCOUNT);
 
 	if (!cbrlo_page)
 		return -ENOMEM;

-- 
2.53.0