Messages in this thread | | | Date | Mon, 23 Sep 2019 17:08:38 -0400 | From | Andrea Arcangeli <> | Subject | Re: [PATCH 15/17] KVM: retpolines: x86: eliminate retpoline from vmx.c exit handlers |
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Hello,
On Mon, Sep 23, 2019 at 01:23:49PM -0700, Sean Christopherson wrote: > The attached patch should do the trick.
The two most attractive options to me remains what I already have implemented under #ifdef CONFIG_RETPOLINE with direct calls (optionally replacing the "if" with a small "switch" still under CONFIG_RETPOLINE if we give up the prioritization of the checks), or the replacement of kvm_vmx_exit_handlers with a switch() as suggested by Vitaly which would cleanup some code.
The intermediate solution that makes "const" work, has the cons of forcing to parse EXIT_REASON_VMCLEAR and the other vmx exit reasons twice, first through a pointer to function (or another if or switch statement) then with a second switch() statement.
If we'd use a single switch statement per Vitaly's suggestion, the "if nested" would better be more simply implemented as:
switch (exit_reason) { case EXIT_REASON_VMCLEAR: if (nested) return handle_vmclear(vcpu); else return handle_vmx_instruction(vcpu); case EXIT_REASON_VMCLEAR: if (nested) [..]
This also removes the compiler dependency to auto inline handle_vmclear in the added nested_vmx_handle_vmx_instruction extern call.
VMREAD/WRITE/RESUME are the most frequent vmexit in l0 while nested runs in l2.
Thanks, Andrea
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