[Xen-changelog] [xen stable-4.3] Nested VMX: prohibit virtual vmentry/vmexit during IO emulation

[patchbot@xxxxxxx]

commit affb7e6bc3d3db4880613cf012b8f6cee0fd9c07
Author:     Yang Zhang <yang.z.zhang@xxxxxxxxx>
AuthorDate: Wed Jan 29 11:55:41 2014 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jan 29 11:55:41 2014 +0100

    Nested VMX: prohibit virtual vmentry/vmexit during IO emulation
    
    Sometimes, L0 needs to decode L2's instruction to handle IO access directly.
    And L0 may get X86EMUL_RETRY when handling this IO request. At same time, if
    there is a virtual vmexit pending (for example, an interrupt pending to 
inject
    to L1) and hypervisor will switch the VCPU context from L2 to L1. Now we
    already are in L1's context, but since we got a X86EMUL_RETRY just now and
    this means hypervisor will retry to handle the IO request later and
    unfortunately, the retry will happen in L1's context. And it will cause the
    problem. The fixing is that if there is a pending IO request, no virtual
    vmexit/vmentry is allowed.
    
    Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
    Acked-by: Jun Nakajima <jun.nakajima@xxxxxxxxx>
    master commit: 09bb434748af9bfe3f7fca4b6eef721a7d5042a4
    master date: 2014-01-23 10:27:34 +0100
---
 xen/arch/x86/hvm/vmx/vvmx.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
index aad108c..cbf3203 100644
--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -1395,6 +1395,13 @@ void nvmx_switch_guest(void)
     struct cpu_user_regs *regs = guest_cpu_user_regs();
 
     /*
+     * a pending IO emualtion may still no finished. In this case,
+     * no virtual vmswith is allowed. Or else, the following IO
+     * emulation will handled in a wrong VCPU context.
+     */
+    if ( get_ioreq(v)->state != STATE_IOREQ_NONE )
+        return;
+    /*
      * a softirq may interrupt us between a virtual vmentry is
      * just handled and the true vmentry. If during this window,
      * a L1 virtual interrupt causes another virtual vmexit, we
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.3

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