linux-kernel - Re: [PATCH v13 44/48] KVM: selftests: Stuff RAX/RCX with 'safe' values in vmmcall()/vmcall()

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Date:   Tue, 1 Nov 2022 15:21:38 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        Yuan Yao <yuan.yao@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v13 44/48] KVM: selftests: Stuff RAX/RCX with 'safe'
 values in vmmcall()/vmcall()

On Tue, Nov 01, 2022, Vitaly Kuznetsov wrote:
> vmmcall()/vmcall() are used to exit from L2 to L1 and no concrete hypercall
> ABI is currenty followed. With the introduction of Hyper-V L2 TLB flush
> it becomes (theoretically) possible that L0 will take responsibility for
> handling the call and no L1 exit will happen. Prevent this by stuffing RAX
> (KVM ABI) and RCX (Hyper-V ABI) with 'safe' values.
> 
> While on it, convert vmmcall() to 'static inline', make it setup stack
> frame and move to include/x86_64/svm_util.h.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@...gle.com>