Re: Always false condition in rmap_add

[Joerg Roedel <joro@8bytes.org>]

On Thu, Nov 11, 2010 at 06:38:47PM +0000, Prasad Joshi wrote:
> Hello All,
> 
> I have question on code of rmap_add
> 
> Here is the code of the function
> 
>  613 static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
>  614 {
> 
> 624     rmapp = gfn_to_rmap(vcpu->kvm, gfn, sp->role.level);
>  625     if (!*rmapp) {
>  626         rmap_printk("rmap_add: %p %llx 0->1\n", spte, *spte);
>  627         *rmapp = (unsigned long)spte;
>  628     } else if (!(*rmapp & 1)) {
>  629         rmap_printk("rmap_add: %p %llx 1->many\n", spte, *spte);
>  630         desc = mmu_alloc_rmap_desc(vcpu);
>  631         desc->sptes[0] = (u64 *)*rmapp;
>  632         desc->sptes[1] = spte;
>  633         *rmapp = (unsigned long)desc | 1;
>  634         ++count;
>  635     } else {
> 
> The line 628 checks whether the last bit of the rmapp is 1.
> If it is one then line 633 assigns a new value to rmapp with and sets
> the last bit to 1.

No, line 628 checks if the last bit is not 1, so the check works.

	Joerg