From 87da7e66a40532b743cd50972fcf85a1f15b14ea Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Wed, 24 Oct 2012 14:07:59 +0800 Subject: 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] [] kvm_get_cr8+0x1d/0x28 [kvm] [23154.861677] [] kvm_arch_vcpu_ioctl_run+0xcda/0xe45 [kvm] [23154.863604] [] ? 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 Signed-off-by: Marcelo Tosatti --- include/linux/kvm_host.h | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) (limited to 'include') diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 93bfc9f9815c..ecc554374e44 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, -- cgit v1.2.3