Commit 255cbecf authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Paolo Bonzini
Browse files

KVM: x86: allocate vcpu->arch.cpuid_entries dynamically 



The current limit for guest CPUID leaves (KVM_MAX_CPUID_ENTRIES, 80)
is reported to be insufficient but before we bump it let's switch to
allocating vcpu->arch.cpuid_entries[] array dynamically. Currently,
'struct kvm_cpuid_entry2' is 40 bytes so vcpu->arch.cpuid_entries is
3200 bytes which accounts for 1/4 of the whole 'struct kvm_vcpu_arch'
but having it pre-allocated (for all vCPUs which we also pre-allocate)
gives us no real benefits.

Another plus of the dynamic allocation is that we now do kvm_check_cpuid()
check before we assign anything to vcpu->arch.cpuid_nent/cpuid_entries so
no changes are made in case the check fails.

Opportunistically remove unneeded 'out' labels from
kvm_vcpu_ioctl_set_cpuid()/kvm_vcpu_ioctl_set_cpuid2() and return
directly whenever possible.

Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20201001130541.1398392-3-vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
parent f69858fc

arch/x86/include/asm/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -637,7 +637,7 @@ struct kvm_vcpu_arch { 
	int halt_request; /* real mode on Intel only */



	int cpuid_nent;

	struct kvm_cpuid_entry2 cpuid_entries[KVM_MAX_CPUID_ENTRIES];

	struct kvm_cpuid_entry2 *cpuid_entries;



	int maxphyaddr;

	int max_tdp_level;

arch/x86/kvm/cpuid.c

+51 −38
Original line number Diff line number Diff line
@@ -217,46 +217,53 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu, 
			     struct kvm_cpuid_entry __user *entries)

{

	int r, i;

	struct kvm_cpuid_entry *cpuid_entries = NULL;

	struct kvm_cpuid_entry *e = NULL;

	struct kvm_cpuid_entry2 *e2 = NULL;



	r = -E2BIG;

	if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)

		goto out;

		return -E2BIG;



	if (cpuid->nent) {

		cpuid_entries = vmemdup_user(entries,

					     array_size(sizeof(struct kvm_cpuid_entry),

							cpuid->nent));

		if (IS_ERR(cpuid_entries)) {

			r = PTR_ERR(cpuid_entries);

			goto out;

		e = vmemdup_user(entries, array_size(sizeof(*e), cpuid->nent));

		if (IS_ERR(e))

			return PTR_ERR(e);



		e2 = kvmalloc_array(cpuid->nent, sizeof(*e2), GFP_KERNEL_ACCOUNT);

		if (!e2) {

			r = -ENOMEM;

			goto out_free_cpuid;

		}

	}

	for (i = 0; i < cpuid->nent; i++) {

		vcpu->arch.cpuid_entries[i].function = cpuid_entries[i].function;

		vcpu->arch.cpuid_entries[i].eax = cpuid_entries[i].eax;

		vcpu->arch.cpuid_entries[i].ebx = cpuid_entries[i].ebx;

		vcpu->arch.cpuid_entries[i].ecx = cpuid_entries[i].ecx;

		vcpu->arch.cpuid_entries[i].edx = cpuid_entries[i].edx;

		vcpu->arch.cpuid_entries[i].index = 0;

		vcpu->arch.cpuid_entries[i].flags = 0;

		vcpu->arch.cpuid_entries[i].padding[0] = 0;

		vcpu->arch.cpuid_entries[i].padding[1] = 0;

		vcpu->arch.cpuid_entries[i].padding[2] = 0;

		e2[i].function = e[i].function;

		e2[i].eax = e[i].eax;

		e2[i].ebx = e[i].ebx;

		e2[i].ecx = e[i].ecx;

		e2[i].edx = e[i].edx;

		e2[i].index = 0;

		e2[i].flags = 0;

		e2[i].padding[0] = 0;

		e2[i].padding[1] = 0;

		e2[i].padding[2] = 0;

	}

	vcpu->arch.cpuid_nent = cpuid->nent;

	r = kvm_check_cpuid(vcpu->arch.cpuid_entries, cpuid->nent);



	r = kvm_check_cpuid(e2, cpuid->nent);

	if (r) {

		vcpu->arch.cpuid_nent = 0;

		kvfree(cpuid_entries);

		goto out;

		kvfree(e2);

		goto out_free_cpuid;

	}



	kvfree(vcpu->arch.cpuid_entries);

	vcpu->arch.cpuid_entries = e2;

	vcpu->arch.cpuid_nent = cpuid->nent;



	cpuid_fix_nx_cap(vcpu);

	kvm_update_cpuid_runtime(vcpu);

	kvm_vcpu_after_set_cpuid(vcpu);



	kvfree(cpuid_entries);

out:

out_free_cpuid:

	kvfree(e);



	return r;

}
@@ -264,26 +271,32 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu, 
			      struct kvm_cpuid2 *cpuid,

			      struct kvm_cpuid_entry2 __user *entries)

{

	struct kvm_cpuid_entry2 *e2 = NULL;

	int r;



	r = -E2BIG;

	if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)

		goto out;

	r = -EFAULT;

	if (copy_from_user(&vcpu->arch.cpuid_entries, entries,

			   cpuid->nent * sizeof(struct kvm_cpuid_entry2)))

		goto out;

	vcpu->arch.cpuid_nent = cpuid->nent;

	r = kvm_check_cpuid(vcpu->arch.cpuid_entries, cpuid->nent);

		return -E2BIG;



	if (cpuid->nent) {

		e2 = vmemdup_user(entries, array_size(sizeof(*e2), cpuid->nent));

		if (IS_ERR(e2))

			return PTR_ERR(e2);

	}



	r = kvm_check_cpuid(e2, cpuid->nent);

	if (r) {

		vcpu->arch.cpuid_nent = 0;

		goto out;

		kvfree(e2);

		return r;

	}



	kvfree(vcpu->arch.cpuid_entries);

	vcpu->arch.cpuid_entries = e2;

	vcpu->arch.cpuid_nent = cpuid->nent;



	kvm_update_cpuid_runtime(vcpu);

	kvm_vcpu_after_set_cpuid(vcpu);

out:

	return r;



	return 0;

}



int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,

arch/x86/kvm/x86.c

+1 −0
Original line number Diff line number Diff line
@@ -9948,6 +9948,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) 
	kvm_mmu_destroy(vcpu);

	srcu_read_unlock(&vcpu->kvm->srcu, idx);

	free_page((unsigned long)vcpu->arch.pio_data);

	kvfree(vcpu->arch.cpuid_entries);

	if (!lapic_in_kernel(vcpu))

		static_key_slow_dec(&kvm_no_apic_vcpu);

}