%fs PDA & KVM

[Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>]

hm, i just noticed that in vmx_vcpu_run() KVM restores %fs quite late. 

This is a bit awkward under v2.6.21 x86 because there we use %fs for the 
KERNEL_PDA area. Things like 'current' rely on it. So maybe we should 
just do this unconditionally in assembly:

        movl $(__KERNEL_PDA), %edx;
        movl %edx, %fs

it's also a problem with -rt too, which has that whole codepath up to 
the load_fs() call preemptible.

i'm also wondering about this bit:

        kvm_run->exit_type = 0;
        if (fail) {
                kvm_run->exit_type = KVM_EXIT_TYPE_FAIL_ENTRY;
                kvm_run->exit_reason = vmcs_read32(VM_INSTRUCTION_ERROR);
                kvm_cr3_cache_sync(vcpu);
                r = 0;
        } else {
                if (fs_gs_ldt_reload_needed) {
                        load_ldt(ldt_sel);
                        load_fs(fs_sel);

are you sure we dont need an FS reload in the 'fail' case?

	Ingo

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