On Thu, May 24, 2012 at 05:24:34PM +0800, Xiao Guangrong wrote: > In current code, if we map a readonly memory space from host to guest > and the page is not currently mapped in the host, we will get a fault-pfn > and async is not allowed, then the vm will crash > > Address Avi's idea, we introduce readonly memory region to map ROM/ROMD > to the guest > As far as I can tell this implements only ROMD. i.e write access to read only slot will generate IO exit.
> Signed-off-by: Xiao Guangrong <[email protected]> > --- > Documentation/virtual/kvm/api.txt | 9 +++++-- > include/linux/kvm.h | 5 ++- > virt/kvm/kvm_main.c | 43 > ++++++++++++++++++++++++++++++------- > 3 files changed, 44 insertions(+), 13 deletions(-) > > diff --git a/Documentation/virtual/kvm/api.txt > b/Documentation/virtual/kvm/api.txt > index 9301266..e2a82c3 100644 > --- a/Documentation/virtual/kvm/api.txt > +++ b/Documentation/virtual/kvm/api.txt > @@ -857,7 +857,8 @@ struct kvm_userspace_memory_region { > }; > > /* for kvm_memory_region::flags */ > -#define KVM_MEM_LOG_DIRTY_PAGES 1UL > +#define KVM_MEM_LOG_DIRTY_PAGES 1UL > +#define KVM_MEM_READ_ONLY (1UL << 2) > > This ioctl allows the user to create or modify a guest physical memory > slot. When changing an existing slot, it may be moved in the guest > @@ -873,9 +874,11 @@ It is recommended that the lower 21 bits of > guest_phys_addr and userspace_addr > be identical. This allows large pages in the guest to be backed by large > pages in the host. > > -The flags field supports just one flag, KVM_MEM_LOG_DIRTY_PAGES, which > +The flags field supports two flags, KVM_MEM_LOG_DIRTY_PAGES, which > instructs kvm to keep track of writes to memory within the slot. See > -the KVM_GET_DIRTY_LOG ioctl. > +the KVM_GET_DIRTY_LOG ioctl. Another flag is KVM_MEM_READ_ONLY, which > +indicates the guest memory is read-only, that means, guest is only allowed > +to read it. > > When the KVM_CAP_SYNC_MMU capability, changes in the backing of the memory > region are automatically reflected into the guest. For example, an mmap() > diff --git a/include/linux/kvm.h b/include/linux/kvm.h > index 09f2b3a..d178e3d 100644 > --- a/include/linux/kvm.h > +++ b/include/linux/kvm.h > @@ -102,8 +102,9 @@ struct kvm_userspace_memory_region { > }; > > /* for kvm_memory_region::flags */ > -#define KVM_MEM_LOG_DIRTY_PAGES 1UL > -#define KVM_MEMSLOT_INVALID (1UL << 1) > +#define KVM_MEM_LOG_DIRTY_PAGES 1UL > +#define KVM_MEMSLOT_INVALID (1UL << 1) > +#define KVM_MEM_READ_ONLY (1UL << 2) > > /* for KVM_IRQ_LINE */ > struct kvm_irq_level { > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 7e14068..27283e4 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1009,10 +1009,11 @@ out: > return size; > } > > -static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn, > - gfn_t *nr_pages) > +static unsigned long __gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t > gfn, > + gfn_t *nr_pages, bool write) > { > - if (!slot || slot->flags & KVM_MEMSLOT_INVALID) > + if (!slot || slot->flags & KVM_MEMSLOT_INVALID || > + ((slot->flags & KVM_MEM_READ_ONLY) && write)) > return bad_hva(); > > if (nr_pages) > @@ -1021,6 +1022,17 @@ static unsigned long gfn_to_hva_many(struct > kvm_memory_slot *slot, gfn_t gfn, > return gfn_to_hva_memslot(slot, gfn); > } > > +static unsigned long gfn_to_hva_many(struct kvm_memory_slot *slot, gfn_t gfn, > + gfn_t *nr_pages) > +{ > + return __gfn_to_hva_many(slot, gfn, nr_pages, true); > +} > + > +unsigned long gfn_to_hva_prot(struct kvm *kvm, gfn_t gfn, bool write) > +{ > + return __gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL, write); > +} > + > unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn) > { > return gfn_to_hva_many(gfn_to_memslot(kvm, gfn), gfn, NULL); > @@ -1053,6 +1065,21 @@ static inline int check_user_page_hwpoison(unsigned > long addr) > return rc == -EHWPOISON; > } > > +static bool vma_is_avalid(struct vm_area_struct *vma, bool write_fault) > +{ > + if (write_fault) { > + if (unlikely(!(vma->vm_flags & VM_WRITE))) > + return false; > + > + return true; > + } > + > + if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) > + return false; > + > + return true; > +} > + > static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic, > bool *async, bool write_fault, bool *writable) > { > @@ -1076,7 +1103,6 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long > addr, bool atomic, > > if (writable) > *writable = write_fault; > - > if (async) { > down_read(¤t->mm->mmap_sem); > npages = get_user_page_nowait(current, current->mm, > @@ -1123,8 +1149,9 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long > addr, bool atomic, > vma->vm_pgoff; > BUG_ON(!kvm_is_mmio_pfn(pfn)); > } else { > - if (async && (vma->vm_flags & VM_WRITE)) > + if (async && vma_is_avalid(vma, write_fault)) > *async = true; > + > pfn = get_fault_pfn(); > } > up_read(¤t->mm->mmap_sem); > @@ -1148,7 +1175,7 @@ static pfn_t __gfn_to_pfn(struct kvm *kvm, gfn_t gfn, > bool atomic, bool *async, > if (async) > *async = false; > > - addr = gfn_to_hva(kvm, gfn); > + addr = gfn_to_hva_prot(kvm, gfn, write_fault); > if (kvm_is_error_hva(addr)) { > get_page(bad_page); > return page_to_pfn(bad_page); > @@ -1293,7 +1320,7 @@ int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, > void *data, int offset, > int r; > unsigned long addr; > > - addr = gfn_to_hva(kvm, gfn); > + addr = gfn_to_hva_prot(kvm, gfn, false); > if (kvm_is_error_hva(addr)) > return -EFAULT; > r = __copy_from_user(data, (void __user *)addr + offset, len); > @@ -1331,7 +1358,7 @@ int kvm_read_guest_atomic(struct kvm *kvm, gpa_t gpa, > void *data, > gfn_t gfn = gpa >> PAGE_SHIFT; > int offset = offset_in_page(gpa); > > - addr = gfn_to_hva(kvm, gfn); > + addr = gfn_to_hva_prot(kvm, gfn, false); > if (kvm_is_error_hva(addr)) > return -EFAULT; > pagefault_disable(); > -- > 1.7.7.6 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
