1 Reply Latest reply on Oct 24, 2014 6:51 AM by ozone

    About INTR intercept in  the XEN HVM with SVM

    xjtudso
      How does xen intercept the phyical INTR

      Hi, guys.

      In XEN VMM, when running a guest with SVM support, the vmm excutes clgi to mask the interrupt and excutes stgi when guest exit.(in the code arch/x86/hvm/Svm/entry.S)

      So, when the guest is running, the physical interrupt is masked. How can xen catch the INTR signal when the physical interrupt dispached during the excution of the guest?

       

      Thanks.

        • Re: About INTR intercept in  the XEN HVM with SVM
          ozone

          GIF is implicitly cleared (interrupts are unmasked) by vmrun and implicitly set with #VMEXIT.

          AMD64 Architecture Programmer's Manual Volume 2: System Programming, 15.5.1, Loading Guest State, p. 450:

          After all guest state is loaded, and intercepts and other control bits are set up, the processor reenables interrupts by setting GIF to 1

          AMD64 Architecture Programmer's Manual Volume 2: System Programming, 15.6, #VMEXIT, p. 452:

           

          Disables interrupts by clearing the GIF, so that after the #VMEXIT, VMM software can complete the state switch atomically.

          svm