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Re: [Xen-devel] [PATCH v4 2/2] x86/PV: support data breakpoint extension registers

On Wed, 2014-04-16 at 15:34 +0100, Jan Beulich wrote:
> @@ -583,6 +593,7 @@ struct xen_domctl_ext_vcpucontext {
>      uint16_t         sysenter_callback_cs;
>      uint8_t          syscall32_disables_events;
>      uint8_t          sysenter_disables_events;
> +    uint16_t         msr_count;
>  #if defined(__GNUC__)
>      union {
>          uint64_aligned_t mcg_cap;
> @@ -591,6 +602,7 @@ struct xen_domctl_ext_vcpucontext {
>  #else
>      struct hvm_vmce_vcpu vmce;
>  #endif
> +    XEN_GUEST_HANDLE_64(xen_domctl_ext_vcpu_msr_t) msrs;

I must be missing something because I can't see where the tools are
initialising msrs, nor does the hypervisor appear to check it is valid
before trying to save stuff to it (although that would be caught by the
copy_to_user I expect).

Also how does one go about determining the correct msr_count before
retrieving this state?

(I have a feeling I asked this before, but I can't find any references.
Perhaps it was in the context of the similar HVM patch...)


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