Re: [PATCH v5 4/9] KVM: MMU: introduce gfn_to_pfn_atomic() function

[Xiao Guangrong]

Xiao Guangrong wrote:

> +             if (atomic)
> +                     goto return_bad_page;
> +
>               down_read(&current->mm->mmap_sem);
>               if (is_hwpoison_address(addr)) {
>                       up_read(&current->mm->mmap_sem);
> @@ -959,6 +965,7 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long 
> addr)
>               if (vma == NULL || addr < vma->vm_start ||
>                   !(vma->vm_flags & VM_PFNMAP)) {
>                       up_read(&current->mm->mmap_sem);
> +return_bad_page:
>                       get_page(bad_page);
>                       return page_to_pfn(bad_page);
>               }
> @@ -972,7 +979,7 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long 
> addr)
>       return pfn;

This patch is broken caused by commit b4f8c24994, rebase it on next branch

Subject: [PATCH v6 4/9] KVM: MMU: introduce gfn_to_pfn_atomic() function

Introduce gfn_to_pfn_atomic(), it's the fast path and can used in atomic
context, the later patch will use it

Signed-off-by: Xiao Guangrong <xiaoguangr...@cn.fujitsu.com>
---
 include/linux/kvm_host.h |    1 +
 virt/kvm/kvm_main.c      |   32 +++++++++++++++++++++++++-------
 2 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 8055067..bf20c97 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -296,6 +296,7 @@ void kvm_release_page_dirty(struct page *page);
 void kvm_set_page_dirty(struct page *page);
 void kvm_set_page_accessed(struct page *page);
 
+pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn);
 pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn);
 pfn_t gfn_to_pfn_memslot(struct kvm *kvm,
                         struct kvm_memory_slot *slot, gfn_t gfn);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b78b794..55a61b7 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -943,19 +943,25 @@ unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(gfn_to_hva);
 
-static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr)
+static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic)
 {
        struct page *page[1];
        int npages;
        pfn_t pfn;
 
-       might_sleep();
-
-       npages = get_user_pages_fast(addr, 1, 1, page);
+       if (atomic)
+               npages = __get_user_pages_fast(addr, 1, 1, page);
+       else {
+               might_sleep();
+               npages = get_user_pages_fast(addr, 1, 1, page);
+       }
 
        if (unlikely(npages != 1)) {
                struct vm_area_struct *vma;
 
+               if (atomic)
+                       goto return_fault_page;
+
                down_read(&current->mm->mmap_sem);
                if (is_hwpoison_address(addr)) {
                        up_read(&current->mm->mmap_sem);
@@ -968,6 +974,7 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr)
                if (vma == NULL || addr < vma->vm_start ||
                    !(vma->vm_flags & VM_PFNMAP)) {
                        up_read(&current->mm->mmap_sem);
+return_fault_page:
                        get_page(fault_page);
                        return page_to_pfn(fault_page);
                }
@@ -981,7 +988,7 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr)
        return pfn;
 }
 
-pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
+pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, bool atomic)
 {
        unsigned long addr;
 
@@ -991,7 +998,18 @@ pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
                return page_to_pfn(bad_page);
        }
 
-       return hva_to_pfn(kvm, addr);
+       return hva_to_pfn(kvm, addr, atomic);
+}
+
+pfn_t gfn_to_pfn_atomic(struct kvm *kvm, gfn_t gfn)
+{
+       return __gfn_to_pfn(kvm, gfn, true);
+}
+EXPORT_SYMBOL_GPL(gfn_to_pfn_atomic);
+
+pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn)
+{
+       return __gfn_to_pfn(kvm, gfn, false);
 }
 EXPORT_SYMBOL_GPL(gfn_to_pfn);
 
@@ -999,7 +1017,7 @@ pfn_t gfn_to_pfn_memslot(struct kvm *kvm,
                         struct kvm_memory_slot *slot, gfn_t gfn)
 {
        unsigned long addr = gfn_to_hva_memslot(slot, gfn);
-       return hva_to_pfn(kvm, addr);
+       return hva_to_pfn(kvm, addr, false);
 }
 
 struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
-- 
1.6.1.2


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