[Xen-changelog] [xen stable-4.10] x86/hvm: fix interaction between internal and external emulation

[patchbot@xxxxxxx]

commit fd07c6d0f004286c7005e8d8f6fce26140da3746
Author:     Paul Durrant <paul.durrant@xxxxxxxxxx>
AuthorDate: Tue Nov 28 14:05:19 2017 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Dec 1 18:13:50 2017 +0000

    x86/hvm: fix interaction between internal and external emulation
    
    A call to handle_hvm_io_completion() is needed for completing I/O
    that requires external emulation. Such completion should be requested when
    hvm_vcpu_io_need_completion() returns true after hvm_emulate_once() has
    completed. This is indicative of the underlying I/O emulation having
    returned X86EMUL_RETRY and hence a re-emulation of the instruction is
    needed to pick up the result of the I/O.
    
    A call to handle_hvm_io_completion() is NOT needed when the underlying
    I/O has not returned X86EMUL_RETRY since there will be no result to pick
    up. Hence it bogus to request such completion when mmio_retry is set,
    since this can only happen if the underlying I/O emulation has returned
    X86EMUL_OKAY (meaning the I/O has completed successfully).
    
    Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Release-acked-by: Julien Grall <julien.grall@xxxxxxxxxx>
    (cherry picked from commit 9c9384d6d8184ca6d21975ccf4e4f72b560540cc)
---
 xen/arch/x86/hvm/io.c           | 2 +-
 xen/arch/x86/hvm/vmx/realmode.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c
index e449b41..9d9e1b0 100644
--- a/xen/arch/x86/hvm/io.c
+++ b/xen/arch/x86/hvm/io.c
@@ -88,7 +88,7 @@ bool hvm_emulate_one_insn(hvm_emulate_validate_t *validate, 
const char *descr)
 
     rc = hvm_emulate_one(&ctxt);
 
-    if ( hvm_vcpu_io_need_completion(vio) || vio->mmio_retry )
+    if ( hvm_vcpu_io_need_completion(vio) )
         vio->io_completion = HVMIO_mmio_completion;
     else
         vio->mmio_access = (struct npfec){};
diff --git a/xen/arch/x86/hvm/vmx/realmode.c b/xen/arch/x86/hvm/vmx/realmode.c
index 03dea6c..11211c8 100644
--- a/xen/arch/x86/hvm/vmx/realmode.c
+++ b/xen/arch/x86/hvm/vmx/realmode.c
@@ -103,7 +103,7 @@ void vmx_realmode_emulate_one(struct hvm_emulate_ctxt 
*hvmemul_ctxt)
 
     rc = hvm_emulate_one(hvmemul_ctxt);
 
-    if ( hvm_vcpu_io_need_completion(vio) || vio->mmio_retry )
+    if ( hvm_vcpu_io_need_completion(vio) )
         vio->io_completion = HVMIO_realmode_completion;
 
     if ( rc == X86EMUL_UNHANDLEABLE )
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.10

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