Re: [PATCH v5 3/7] kvm: Make init_rmode_identity_map() return 0 on success.

Paolo Bonzini
2014-09-11T09:17:45Z

Il 11/09/2014 07:38, Tang Chen ha scritto:
> In init_rmode_identity_map(), there two variables indicating the return
> value, r and ret, and it return 0 on error, 1 on success. The function
> is only called by vmx_create_vcpu(), and r is redundant.
>
> This patch removes the redundant variable r, and make init_rmode_identity_map()
> return 0 on success, -errno on failure.
>
> Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
> ---
> arch/x86/kvm/vmx.c | 25 +++++++++++--------------
> 1 file changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 953d529..63c4c3e 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -3939,45 +3939,42 @@ out:
>
> static int init_rmode_identity_map(struct kvm *kvm)
> {
> - int i, idx, r, ret = 0;
> + int i, idx, ret = 0;
> pfn_t identity_map_pfn;
> u32 tmp;
>
> if (!enable_ept)
> - return 1;
> + return 0;
>
> /* Protect kvm->arch.ept_identity_pagetable_done. */
> mutex_lock(&kvm->slots_lock);
>
> - if (likely(kvm->arch.ept_identity_pagetable_done)) {
> - ret = 1;
> + if (likely(kvm->arch.ept_identity_pagetable_done))
> goto out2;
> - }
>
> identity_map_pfn = kvm->arch.ept_identity_map_addr >> PAGE_SHIFT;
>
> - r = alloc_identity_pagetable(kvm);
> - if (r)
> + ret = alloc_identity_pagetable(kvm);
> + if (ret)
> goto out2;
>
> idx = srcu_read_lock(&kvm->srcu);
> - r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE);
> - if (r < 0)
> + ret = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE);
> + if (ret)
> goto out;
> /* Set up identity-mapping pagetable for EPT in real mode */
> for (i = 0; i < PT32_ENT_PER_PAGE; i++) {
> tmp = (i << 22) + (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER |
> _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_PSE);
> - r = kvm_write_guest_page(kvm, identity_map_pfn,
> + ret = kvm_write_guest_page(kvm, identity_map_pfn,
> &tmp, i * sizeof(tmp), sizeof(tmp));
> - if (r < 0)
> + if (ret)
> goto out;
> }
> kvm->arch.ept_identity_pagetable_done = true;
> - ret = 1;
> +
> out:
> srcu_read_unlock(&kvm->srcu, idx);
> -
> out2:
> mutex_unlock(&kvm->slots_lock);
> return ret;
> @@ -7645,7 +7642,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> kvm->arch.ept_identity_map_addr =
> VMX_EPT_IDENTITY_PAGETABLE_ADDR;
> err = -ENOMEM;
> - if (!init_rmode_identity_map(kvm))
> + if (init_rmode_identity_map(kvm))

Please add "< 0" here. I would also consider setting err to the return
value of init_rmode_identity_map, and initializing it to -ENOMEM only
after the "if".

Paolo

> goto free_vmcs;