Re: [PATCH v2 1/3] x86/vmx: implement Bus Lock detection

[Andrew Cooper <Andrew.Cooper3@citrix.com>]

On 26/05/2022 12:11, Roger Pau Monne wrote:
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index f08a00dcbb..476ab72463 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -4065,6 +4065,16 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
>  
>      if ( unlikely(exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY) )
>          return vmx_failed_vmentry(exit_reason, regs);
> +    if ( unlikely(exit_reason & VMX_EXIT_REASONS_BUS_LOCK) )
> +    {
> +        /*
> +         * Delivery of Bus Lock VM exit was pre-empted by a higher priority VM
> +         * exit.
> +         */
> +        exit_reason &= ~VMX_EXIT_REASONS_BUS_LOCK;
> +        if ( exit_reason != EXIT_REASON_BUS_LOCK )
> +            perfc_incr(buslock);
> +    }

I know this post-dates you posting v2, but given the latest update from
Intel, VMX_EXIT_REASONS_BUS_LOCK will be set on all exits.

So the code logic would be simpler as:

if ( exit_reason & VMX_EXIT_REASONS_BUS_LOCK )
{
    perfc_incr(buslock);
    exit_reason &= ~VMX_EXIT_REASONS_BUS_LOCK;
}

and ...

>  
>      if ( v->arch.hvm.vmx.vmx_realmode )
>      {
> @@ -4561,6 +4571,14 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
>          vmx_handle_descriptor_access(exit_reason);
>          break;
>  
> +    case EXIT_REASON_BUS_LOCK:
> +        perfc_incr(buslock);

... dropping this perf counter.

With something along these lines, Reviewed-by: Andrew Cooper
<andrew.cooper3@citrix.com>