On Fri, Sep 25, 2020 at 02:22:41PM -0700, Ben Gardon wrote:
> +static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> + unsigned int pte_access, int level,
> + gfn_t gfn, kvm_pfn_t pfn, bool speculative,
> + bool can_unsync, bool host_writable)
> +{
> + u64 spte = 0;
> + struct kvm_mmu_page *sp;
> + int ret = 0;
> +
> + if (set_mmio_spte(vcpu, sptep, gfn, pfn, pte_access))
> + return 0;
> +
> + sp = sptep_to_sp(sptep);
> +
> + spte = make_spte(vcpu, pte_access, level, gfn, pfn, *sptep, speculative,
> + can_unsync, host_writable, sp_ad_disabled(sp), &ret);
> + if (!spte)
> + return 0;
This is an impossible condition. Well, maybe it's theoretically possible
if page track is active, with EPT exec-only support (shadow_present_mask is
zero), and pfn==0. But in that case, returning early is wrong.
Rather than return the spte, what about returning 'ret', passing 'new_spte'
as a u64 *, and dropping the bail early path? That would also eliminate
the minor wart of make_spte() relying on the caller to initialize 'ret'.
> +
> + if (spte & PT_WRITABLE_MASK)
> + kvm_vcpu_mark_page_dirty(vcpu, gfn);
> +
> if (mmu_spte_update(sptep, spte))
> ret |= SET_SPTE_NEED_REMOTE_TLB_FLUSH;
> return ret;
> --
> 2.28.0.709.gb0816b6eb0-goog
>
