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authorXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>2012-10-24 14:07:59 +0800
committerMarcelo Tosatti <mtosatti@redhat.com>2012-10-31 20:36:30 -0200
commit87da7e66a40532b743cd50972fcf85a1f15b14ea (patch)
treee553258648881176136774013f0fecff876644bb /include/linux/kvm_host.h
parent35fd3dc58da675d659513384221349ef90749a01 (diff)
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KVM: x86: fix vcpu->mmio_fragments overflow
After commit b3356bf0dbb349 (KVM: emulator: optimize "rep ins" handling), the pieces of io data can be collected and write them to the guest memory or MMIO together Unfortunately, kvm splits the mmio access into 8 bytes and store them to vcpu->mmio_fragments. If the guest uses "rep ins" to move large data, it will cause vcpu->mmio_fragments overflow The bug can be exposed by isapc (-M isapc): [23154.818733] general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC [ ......] [23154.858083] Call Trace: [23154.859874] [<ffffffffa04f0e17>] kvm_get_cr8+0x1d/0x28 [kvm] [23154.861677] [<ffffffffa04fa6d4>] kvm_arch_vcpu_ioctl_run+0xcda/0xe45 [kvm] [23154.863604] [<ffffffffa04f5a1a>] ? kvm_arch_vcpu_load+0x17b/0x180 [kvm] Actually, we can use one mmio_fragment to store a large mmio access then split it when we pass the mmio-exit-info to userspace. After that, we only need two entries to store mmio info for the cross-mmio pages access Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'include/linux/kvm_host.h')
-rw-r--r--include/linux/kvm_host.h15
1 files changed, 2 insertions, 13 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 93bfc9f..ecc5543 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -42,19 +42,8 @@
*/
#define KVM_MEMSLOT_INVALID (1UL << 16)
-/*
- * If we support unaligned MMIO, at most one fragment will be split into two:
- */
-#ifdef KVM_UNALIGNED_MMIO
-# define KVM_EXTRA_MMIO_FRAGMENTS 1
-#else
-# define KVM_EXTRA_MMIO_FRAGMENTS 0
-#endif
-
-#define KVM_USER_MMIO_SIZE 8
-
-#define KVM_MAX_MMIO_FRAGMENTS \
- (KVM_MMIO_SIZE / KVM_USER_MMIO_SIZE + KVM_EXTRA_MMIO_FRAGMENTS)
+/* Two fragments for cross MMIO pages. */
+#define KVM_MAX_MMIO_FRAGMENTS 2
/*
* For the normal pfn, the highest 12 bits should be zero,
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