Re: [Xen-devel] [PATCH v2 4/5] x86/msr: Handle MSR_TSC_AUX consistently for PV and HVM guests

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.11.18 at 15:37, <andrew.cooper3@xxxxxxxxxx> wrote:
> With PVRDTSCP mode removed, handling of MSR_TSC_AUX can move into the common
> code.  Move its storage into struct vcpu_msrs (dropping the HVM-specific
> msr_tsc_aux), and add an RDPID feature check as this bit also enumerates the
> presence of the MSR.
> 
> Introduce cpu_has_rdpid along with the synthesized cpu_has_msr_tsc_aux to
> correct the context switch paths, as MSR_TSC_AUX is enumerated by either
> RDTSCP or RDPID.
> 
> Drop hvm_msr_tsc_aux() entirely, and use v->arch.msrs->tsc_aux directly.
> Update hvm_load_cpu_ctxt() to check that the incoming ctxt.msr_tsc_aux isn't
> out of range.  In practice, no previous version of Xen ever wrote an
> out-of-range value.  Add MSR_TSC_AUX to the list of MSRs migrated for PV
> guests, but leave the HVM path using the existing space in hvm_hw_cpu.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>[...]
> ---
>  xen/arch/x86/domain.c            |  5 ++---
>  xen/arch/x86/domctl.c            |  2 ++
>  xen/arch/x86/hvm/hvm.c           | 22 +++++++++-------------
>  xen/arch/x86/hvm/svm/svm.c       |  6 +++---
>  xen/arch/x86/hvm/vmx/vmx.c       |  6 +++---
>  xen/arch/x86/msr.c               | 18 ++++++++++++++++++
>  xen/arch/x86/pv/emul-priv-op.c   |  4 ----
>  xen/include/asm-x86/cpufeature.h |  5 +++++
>  xen/include/asm-x86/hvm/hvm.h    |  6 ------
>  xen/include/asm-x86/hvm/vcpu.h   |  1 -
>  xen/include/asm-x86/msr.h        |  9 +++++++++
>  11 files changed, 51 insertions(+), 33 deletions(-)

Btw. by the end of this series wouldn't you agree docs/misc/pvrdtscp.c
should be gone? And won't docs/man/xen-tsc-mode.pod.7 need
adjustment too?

Jan



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