Re: [PATCH v12 65/84] KVM: LoongArch: Mark "struct page" pfns accessed only in "slow" page fault path

maobibo
2024-08-02T07:34:52Z

On 2024/7/27 上午7:52, Sean Christopherson wrote:
> Mark pages accessed only in the slow path, before dropping mmu_lock when
> faulting in guest memory so that LoongArch can convert to
> kvm_release_faultin_page() without tripping its lockdep assertion on
> mmu_lock being held.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/loongarch/kvm/mmu.c | 20 ++------------------
> 1 file changed, 2 insertions(+), 18 deletions(-)
>
> diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c
> index 364dd35e0557..52b5c16cf250 100644
> --- a/arch/loongarch/kvm/mmu.c
> +++ b/arch/loongarch/kvm/mmu.c
> @@ -552,12 +552,10 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
> static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool write)
> {
> int ret = 0;
> - kvm_pfn_t pfn = 0;
> kvm_pte_t *ptep, changed, new;
> gfn_t gfn = gpa >> PAGE_SHIFT;
> struct kvm *kvm = vcpu->kvm;
> struct kvm_memory_slot *slot;
> - struct page *page;
>
> spin_lock(&kvm->mmu_lock);
>
> @@ -570,8 +568,6 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ
>
> /* Track access to pages marked old */
> new = kvm_pte_mkyoung(*ptep);
> - /* call kvm_set_pfn_accessed() after unlock */
> -
> if (write && !kvm_pte_dirty(new)) {
> if (!kvm_pte_write(new)) {
> ret = -EFAULT;
> @@ -595,23 +591,11 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ
> }
>
> changed = new ^ (*ptep);
> - if (changed) {
> + if (changed)
> kvm_set_pte(ptep, new);
> - pfn = kvm_pte_pfn(new);
> - page = kvm_pfn_to_refcounted_page(pfn);
> - if (page)
> - get_page(page);
> - }
> +
> spin_unlock(&kvm->mmu_lock);
>
> - if (changed) {
> - if (kvm_pte_young(changed))
> - kvm_set_pfn_accessed(pfn);
> -
> - if (page)
> - put_page(page);
> - }
> -
> if (kvm_pte_dirty(changed))
> mark_page_dirty(kvm, gfn);
>
>
Reviewed-by: Bibo Mao <maobibo@loongson.cn>