Re: [bug report] KVM: x86: avoid incorrect writes to host MSR_IA32_SPEC_CTRL

[Sean Christopherson <sean.j.christopherson@intel.com>]

On Mon, Jan 27, 2020 at 09:04:22AM +0300, Dan Carpenter wrote:
> Hello Paolo Bonzini,
> 
> The patch e71ae535bc24: "KVM: x86: avoid incorrect writes to host
> MSR_IA32_SPEC_CTRL" from Jan 20, 2020, leads to the following static
> checker warning:
> 
> 	arch/x86/kvm/vmx/vmx.c:2001 vmx_set_msr()
> 	warn: maybe use && instead of &
> 
> arch/x86/kvm/vmx/vmx.c
>   1994                  vmx->msr_ia32_umwait_control = data;
>   1995                  break;
>   1996          case MSR_IA32_SPEC_CTRL:
>   1997                  if (!msr_info->host_initiated &&
>   1998                      !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL))
>   1999                          return 1;
>   2000  
>   2001                  if (data & ~kvm_spec_ctrl_valid_bits(vcpu))
>                                    ^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> This seems wrong.  kvm_spec_ctrl_valid_bits() returns a bool so this
> is either 0xffffffff or 0xfffffffe.  data is a u64.
> 
>   2002                          return 1;
>   2003  
>   2004                  vmx->spec_ctrl = data;
>   2005                  if (!data)
>   2006                          break;
>   2007  
>   2008                  /*
>   2009                   * For non-nested:

Paolo already had to put on the cone of shame for this one :-)

https://lkml.kernel.org/r/6b725990-f0c2-6577-be7e-44e101e540b5@redhat.com