lkml.org 
[lkml]   [2012]   [May]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] KVM: fix async page fault working for readonly mapping
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

The reason is only writable vma can be allowed to be async in current
code

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
---
virt/kvm/kvm_main.c | 19 +++++++++++++++++--
1 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6bd34a6..b6c8962 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1052,6 +1052,21 @@ 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)
{
@@ -1075,7 +1090,6 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,

if (writable)
*writable = write_fault;
-
if (async) {
down_read(&current->mm->mmap_sem);
npages = get_user_page_nowait(current, current->mm,
@@ -1122,8 +1136,9 @@ 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(&current->mm->mmap_sem);
--
1.7.7.6


\
 
 \ /
  Last update: 2012-05-21 09:41    [W:0.119 / U:0.952 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site