On 2024/6/22 下午1:21, Huacai Chen wrote:
Hi, Bibo, What is the relationship between this patch and the below one? https://lore.kernel.org/loongarch/20240611034609.3442344-1-maobibo@xxxxxxxxxxx/T/#u
It is updated version about the patch listed at this website, I put all migration relative patches into one patch set, to prevent that it is lost in so many mail threads:)
Regards Bibo Mao
Huacai On Wed, Jun 19, 2024 at 4:09 PM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:Function kvm_map_page_fast() is fast path of secondary mmu page fault flow, pfn is parsed from secondary mmu page table walker. However the corresponding page reference is not added, it is dangerious to access page out of mmu_lock. Here page ref is added inside mmu_lock, function kvm_set_pfn_accessed() and kvm_set_pfn_dirty() is called with page ref added, so that the page will not be freed by others. Also kvm_set_pfn_accessed() is removed here since it is called in the following function kvm_release_pfn_clean(). Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx> --- arch/loongarch/kvm/mmu.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c index 3b862f3a72cb..5a820a81fd97 100644 --- a/arch/loongarch/kvm/mmu.c +++ b/arch/loongarch/kvm/mmu.c @@ -557,6 +557,7 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ gfn_t gfn = gpa >> PAGE_SHIFT; struct kvm *kvm = vcpu->kvm; struct kvm_memory_slot *slot; + struct page *page; spin_lock(&kvm->mmu_lock); @@ -599,19 +600,22 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ 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); - /* - * Fixme: pfn may be freed after mmu_lock - * kvm_try_get_pfn(pfn)/kvm_release_pfn pair to prevent this? - */ - if (kvm_pte_young(changed)) - kvm_set_pfn_accessed(pfn); + if (changed) { + if (kvm_pte_young(changed)) + kvm_set_pfn_accessed(pfn); - if (kvm_pte_dirty(changed)) { - mark_page_dirty(kvm, gfn); - kvm_set_pfn_dirty(pfn); + if (kvm_pte_dirty(changed)) { + mark_page_dirty(kvm, gfn); + kvm_set_pfn_dirty(pfn); + } + if (page) + put_page(page); } return ret; out: @@ -920,7 +924,6 @@ static int kvm_map_page(struct kvm_vcpu *vcpu, unsigned long gpa, bool write) kvm_set_pfn_dirty(pfn); } - kvm_set_pfn_accessed(pfn); kvm_release_pfn_clean(pfn); out: srcu_read_unlock(&kvm->srcu, srcu_idx); -- 2.39.3
