[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: Early test for 32- vs 64-bit hvm domain?
Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> writes: > On 30/1/08 00:34, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote: > >>> As long as e.g. Linux has not started (i.e. during bios and grub for >>> instance), you can't know whether that will be a 64bit Linux >>> or a 32bit >>> Linux. >> >> That's what I was afraid of... >> >> Then what is the earliest point in the execution of an x86_64 >> domain/vcpu in *xen* where hvm_long_mode_enabled(v) will work >> properly? E.g. in Linux/x86_64 is long mode set early in __start? >> And is this done via a hypercall or an emulated instruction? > > As sson as you see LME bit get set in the EFER MSR then you know you have a > 64-bit guest. Writes to EFER are emulated in long_mode_do_msr_write() in > vmx.c and svm.c. Those are the places to patch in Xen 3.1 branch. You could do it slightly earlier by intercepting bios int 0x15 eax=0xec00 ebx=2 The kernel issues that to tell the BIOS it is 64bit. That will only work if the boot loader does not skip the real mode code (a few do) -Andi _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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