[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/2] x86/VMX: don't needlessly install VMFUNC emulation hook
>>> On 22.12.16 at 14:47, <andrew.cooper3@xxxxxxxxxx> wrote: > On 22/12/16 08:37, Jan Beulich wrote: >> Instead of checking cpu_has_vmx_vmfunc inside the hook, use it to >> determine whether to install the hook in the first place. >> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> > > I am not so sure about this. > > vmfunc is reachable in the instruction emulator on hardware which > doesn't support vmfunc, and there is explicit provision for using vmfunc > 0 via hypercall on hardware lacking vmfunc support. > > Given that the #VE part of altp2m is always emulated architecturally, I > think there is an argument to be made for also emulating EPTP switching > architecturally as well. I don't understand this argumentation: Without the patch, the hook function checks !cpu_has_vmx_vmfunc (and fails otherwise); with the patch the hook isn't being put in place when !cpu_has_vmx_vmfunc, and failure occurs in hvmemul_vmfunc(). I admit there's the difference in error codes, but we could certainly make hvmemul_vmfunc() return EXCEPTION when there's no hook. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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