Re: [Qemu-devel] [PULL 07/28] x86/cpu: use standard-headers/asm-x86.kvm_para.h

[Michael S. Tsirkin]

On Fri, May 25, 2018 at 12:53:44PM +0100, Peter Maydell wrote:
> On 25 May 2018 at 12:06, Peter Maydell <address@hidden> wrote:
> > On 23 May 2018 at 15:43, Michael S. Tsirkin <address@hidden> wrote:
> >> Switch to the header we imported from Linux,
> >> this allows us to drop a hack in kvm_i386.h.
> >> More code will be dropped in the next patch.
> >>
> >> Signed-off-by: Michael S. Tsirkin <address@hidden>
> >
> >> --- a/target/i386/cpu.h
> >> +++ b/target/i386/cpu.h
> >> @@ -688,8 +688,6 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
> >>  #define CPUID_7_0_EDX_SPEC_CTRL     (1U << 26) /* Speculation Control */
> >>  #define CPUID_7_0_EDX_SPEC_CTRL_SSBD  (1U << 31) /* Speculative Store 
> >> Bypass Disable */
> >>
> >> -#define KVM_HINTS_DEDICATED (1U << 0)
> >> -
> >>  #define CPUID_8000_0008_EBX_IBPB    (1U << 12) /* Indirect Branch 
> >> Prediction Barrier */
> >>
> >>  #define CPUID_XSAVE_XSAVEOPT   (1U << 0)
> >
> > Hi -- this seems like it will break compilation when we next
> > update our copy of the Linux kernel headers, because (as of
> > 4.17-rc6, at least), asm-x86/kvm_para.h doesn't define
> > KVM_HINTS_DEDICATED.
> 
> For the moment I'm using this workaround (I wanted to do a header
> update for something else I'm working on):
> 
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -48,6 +48,11 @@
>  #include "exec/memattrs.h"
>  #include "trace.h"
> 
> +/* Work around this kernel header constant changing its name */
> +#ifndef KVM_HINTS_REALTIME
> +#define KVM_HINTS_REALTIME KVM_HINTS_DEDICATED
> +#endif
> +
>  //#define DEBUG_KVM
> 
>  #ifdef DEBUG_KVM

I don't think we need this chunk.

> @@ -387,7 +392,7 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s,
> uint32_t function,
>              ret &= ~(1U << KVM_FEATURE_PV_UNHALT);
>          }
>      } else if (function == KVM_CPUID_FEATURES && reg == R_EDX) {
> -        ret |= 1U << KVM_HINTS_DEDICATED;
> +        ret |= 1U << KVM_HINTS_REALTIME;
>          found = 1;
>      }

That's the right change when we update this header.

> thanks
> -- PMM