Re: [Xen-devel] [PATCH v19 12/14] x86/VPMU: Merge vpmu_rdmsr and vpmu_wrmsr

[Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>]

Am Dienstag 17 MÃrz 2015, 10:54:09 schrieb Boris Ostrovsky:
> The two routines share most of their logic.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> ---
> Changes in v19:
> * const-ified arch_vpmu_ops in vpmu_do_wrmsr
> * non-changes:
>    - kept 'current' as a non-initializer to avoid unnecessary initialization
>      in the (common) non-VPMU case
>    - kept 'nop' label since there are multiple dissimilar cases that can cause
>      a non-emulation of VPMU access
> 
>  xen/arch/x86/hvm/vpmu.c        | 76 
> +++++++++++++++++-------------------------
>  xen/include/asm-x86/hvm/vpmu.h | 14 ++++++--
>  2 files changed, 42 insertions(+), 48 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/vpmu.c b/xen/arch/x86/hvm/vpmu.c
> index c287d8b..beed956 100644
> --- a/xen/arch/x86/hvm/vpmu.c
> +++ b/xen/arch/x86/hvm/vpmu.c
> @@ -103,63 +103,47 @@ void vpmu_lvtpc_update(uint32_t val)
>          apic_write(APIC_LVTPC, vpmu->hw_lapic_lvtpc);
>  }
>  
> -int vpmu_do_wrmsr(unsigned int msr, uint64_t msr_content, uint64_t supported)
> +int vpmu_do_msr(unsigned int msr, uint64_t *msr_content,
> +                uint64_t supported, bool_t is_write)
>  {
> -    struct vcpu *curr = current;
> +    struct vcpu *curr;
>      struct vpmu_struct *vpmu;
> +    const struct arch_vpmu_ops *ops;

What is this const useful for in this small function?

Reviewed-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>

Dietmar.

> +    int ret = 0;
>  
>      if ( vpmu_mode == XENPMU_MODE_OFF )
> -        return 0;
> +        goto nop;
>  
> +    curr = current;
>      vpmu = vcpu_vpmu(curr);
> -    if ( vpmu->arch_vpmu_ops && vpmu->arch_vpmu_ops->do_wrmsr )
> -    {
> -        int ret = vpmu->arch_vpmu_ops->do_wrmsr(msr, msr_content, supported);
> -
> -        /*
> -         * We may have received a PMU interrupt during WRMSR handling
> -         * and since do_wrmsr may load VPMU context we should save
> -         * (and unload) it again.
> -         */
> -        if ( !is_hvm_vcpu(curr) && vpmu->xenpmu_data &&
> -             (vpmu->xenpmu_data->pmu.pmu_flags & PMU_CACHED) )
> -        {
> -            vpmu_set(vpmu, VPMU_CONTEXT_SAVE);
> -            vpmu->arch_vpmu_ops->arch_vpmu_save(curr);
> -            vpmu_reset(vpmu, VPMU_CONTEXT_SAVE | VPMU_CONTEXT_LOADED);
> -        }
> -        return ret;
> -    }
> -
> -    return 0;
> -}
> -
> -int vpmu_do_rdmsr(unsigned int msr, uint64_t *msr_content)
> -{
> -    struct vcpu *curr = current;
> -    struct vpmu_struct *vpmu;
> +    ops = vpmu->arch_vpmu_ops;
> +    if ( !ops )
> +        goto nop;
> +
> +    if ( is_write && ops->do_wrmsr )
> +        ret = ops->do_wrmsr(msr, *msr_content, supported);
> +    else if ( !is_write && ops->do_rdmsr )
> +        ret = ops->do_rdmsr(msr, msr_content);
> +    else
> +        goto nop;
>  
> -    if ( vpmu_mode == XENPMU_MODE_OFF )
> +    /*
> +     * We may have received a PMU interrupt while handling MSR access
> +     * and since do_wr/rdmsr may load VPMU context we should save
> +     * (and unload) it again.
> +     */
> +    if ( !is_hvm_vcpu(curr) &&
> +         vpmu->xenpmu_data && (vpmu->xenpmu_data->pmu.pmu_flags & 
> PMU_CACHED) )
>      {
> -        *msr_content = 0;
> -        return 0;
> +        vpmu_set(vpmu, VPMU_CONTEXT_SAVE);
> +        ops->arch_vpmu_save(curr);
> +        vpmu_reset(vpmu, VPMU_CONTEXT_SAVE | VPMU_CONTEXT_LOADED);
>      }
>  
> -    vpmu = vcpu_vpmu(curr);
> -    if ( vpmu->arch_vpmu_ops && vpmu->arch_vpmu_ops->do_rdmsr )
> -    {
> -        int ret = vpmu->arch_vpmu_ops->do_rdmsr(msr, msr_content);
> +    return ret;
>  
> -        if ( !is_hvm_vcpu(curr) && vpmu->xenpmu_data &&
> -             (vpmu->xenpmu_data->pmu.pmu_flags & PMU_CACHED) )
> -        {
> -            vpmu_set(vpmu, VPMU_CONTEXT_SAVE);
> -            vpmu->arch_vpmu_ops->arch_vpmu_save(curr);
> -            vpmu_reset(vpmu, VPMU_CONTEXT_SAVE | VPMU_CONTEXT_LOADED);
> -        }
> -        return ret;
> -    }
> -    else
> + nop:
> +    if ( !is_write )
>          *msr_content = 0;
>  
>      return 0;
> diff --git a/xen/include/asm-x86/hvm/vpmu.h b/xen/include/asm-x86/hvm/vpmu.h
> index 642a4b7..63851a7 100644
> --- a/xen/include/asm-x86/hvm/vpmu.h
> +++ b/xen/include/asm-x86/hvm/vpmu.h
> @@ -99,8 +99,8 @@ static inline bool_t vpmu_are_all_set(const struct 
> vpmu_struct *vpmu,
>  }
>  
>  void vpmu_lvtpc_update(uint32_t val);
> -int vpmu_do_wrmsr(unsigned int msr, uint64_t msr_content, uint64_t 
> supported);
> -int vpmu_do_rdmsr(unsigned int msr, uint64_t *msr_content);
> +int vpmu_do_msr(unsigned int msr, uint64_t *msr_content,
> +                uint64_t supported, bool_t is_write);
>  void vpmu_do_interrupt(struct cpu_user_regs *regs);
>  void vpmu_do_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx,
>                                         unsigned int *ecx, unsigned int *edx);
> @@ -110,6 +110,16 @@ void vpmu_save(struct vcpu *v);
>  void vpmu_load(struct vcpu *v);
>  void vpmu_dump(struct vcpu *v);
>  
> +static inline int vpmu_do_wrmsr(unsigned int msr, uint64_t msr_content,
> +                                uint64_t supported)
> +{
> +    return vpmu_do_msr(msr, &msr_content, supported, 1);
> +}
> +static inline int vpmu_do_rdmsr(unsigned int msr, uint64_t *msr_content)
> +{
> +    return vpmu_do_msr(msr, msr_content, 0, 0);
> +}
> +
>  extern int acquire_pmu_ownership(int pmu_ownership);
>  extern void release_pmu_ownership(int pmu_ownership);
>  
> 

-- 
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