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

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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: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20201001130541.1398392-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2020-10-01 15:05:40 +02:00 committed by Paolo Bonzini
parent f69858fcc7
commit 255cbecfe0
3 changed files with 54 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/include/asm/kvm_host.h
View File

@ -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;

91
arch/x86/kvm/cpuid.c
View File

@ -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);
if (r) {
vcpu->arch.cpuid_nent = 0;
goto out;
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) {
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,

1
arch/x86/kvm/x86.c
View File

@ -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);
}