On Fri, Sep 25, 2020 at 02:22:49PM -0700, Ben Gardon wrote:
> In order to avoid creating executable hugepages in the TDP MMU PF
> handler, remove the dependency between disallowed_hugepage_adjust and
> the shadow_walk_iterator. This will open the function up to being used
> by the TDP MMU PF handler in a future patch.
>
> Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
> machine. This series introduced no new failures.
>
> This series can be viewed in Gerrit at:
> https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
>
> Signed-off-by: Ben Gardon <[email protected]>
> ---
> arch/x86/kvm/mmu/mmu.c | 17 +++++++++--------
> arch/x86/kvm/mmu/paging_tmpl.h | 3 ++-
> 2 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 6344e7863a0f5..f6e6fc9959c04 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3295,13 +3295,12 @@ static int kvm_mmu_hugepage_adjust(struct kvm_vcpu
> *vcpu, gfn_t gfn,
> return level;
> }
>
> -static void disallowed_hugepage_adjust(struct kvm_shadow_walk_iterator it,
> - gfn_t gfn, kvm_pfn_t *pfnp, int *levelp)
> +static void disallowed_hugepage_adjust(u64 spte, gfn_t gfn, int cur_level,
> + kvm_pfn_t *pfnp, int *goal_levelp)
> {
> - int level = *levelp;
> - u64 spte = *it.sptep;
> + int goal_level = *goal_levelp;
More bikeshedding... Can we keep 'level' and 'levelp' instead of prepending
'goal_'? I get the intent, but goal_level isn't necessarily accurate as the
original requested level (referred to as req_level in the caller in kvm/queue)
may be different than goal_level, i.e. this helper may have already decremented
the level. IMO it's more accurate/correct to keep the plain 'level'.
> - if (it.level == level && level > PG_LEVEL_4K &&
> + if (cur_level == goal_level && goal_level > PG_LEVEL_4K &&
> is_nx_huge_page_enabled() &&
> is_shadow_present_pte(spte) &&
> !is_large_pte(spte)) {
> @@ -3312,9 +3311,10 @@ static void disallowed_hugepage_adjust(struct
> kvm_shadow_walk_iterator it,
> * patching back for them into pfn the next 9 bits of
> * the address.
> */
> - u64 page_mask = KVM_PAGES_PER_HPAGE(level) -
> KVM_PAGES_PER_HPAGE(level - 1);
> + u64 page_mask = KVM_PAGES_PER_HPAGE(goal_level) -
> + KVM_PAGES_PER_HPAGE(goal_level - 1);
> *pfnp |= gfn & page_mask;
> - (*levelp)--;
> + (*goal_levelp)--;
> }
> }
>
> @@ -3339,7 +3339,8 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t
> gpa, int write,
> * We cannot overwrite existing page tables with an NX
> * large page, as the leaf could be executable.
> */
> - disallowed_hugepage_adjust(it, gfn, &pfn, &level);
> + disallowed_hugepage_adjust(*it.sptep, gfn, it.level,
> + &pfn, &level);
>
> base_gfn = gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
> if (it.level == level)
> diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
> index 4dd6b1e5b8cf7..6a8666cb0d24b 100644
> --- a/arch/x86/kvm/mmu/paging_tmpl.h
> +++ b/arch/x86/kvm/mmu/paging_tmpl.h
> @@ -690,7 +690,8 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gpa_t addr,
> * We cannot overwrite existing page tables with an NX
> * large page, as the leaf could be executable.
> */
> - disallowed_hugepage_adjust(it, gw->gfn, &pfn, &hlevel);
> + disallowed_hugepage_adjust(*it.sptep, gw->gfn, it.level,
> + &pfn, &hlevel);
>
> base_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
> if (it.level == hlevel)
> --
> 2.28.0.709.gb0816b6eb0-goog
>
