[Xen-devel] PVH: iopl

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

I noticed anamoly in my code the way IOPL is set. For vcpu 0, its done
via

        set_iopl.iopl = 1;
        rc = HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);

in xen_start_kernel() in enlighten.c. But, for non boot vcpus, its done
via eflags in cpu_initialize_context():
        ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */

Since I am running in HVM container, IO ops cause vmexit. I can just
check eflags at that point for guest IOPL. So I am thinking of just
using eflags and not doing the hcall.  It will also reduce the need for
another field in the struct pv_vcpu for me. 

(JFYI: EXIT_REASON_IO_INSTRUCTION cause emulate_privileged_op() to be
called).

What do you guys think?

thanks,
mukesh


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