Re: [Xen-devel] [PATCH 8/9] x86/vmx: Support removing MSRs from the host/guest load/save lists

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, May 22, 2018 at 12:20:45PM +0100, Andrew Cooper wrote:
> Up until this point, the MSR load/save lists have only ever accumulated
> content.  Introduce vmx_del_msr() as a companion to vmx_add_msr().
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Jun Nakajima <jun.nakajima@xxxxxxxxx>
> CC: Kevin Tian <kevin.tian@xxxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
>  xen/arch/x86/hvm/vmx/vmcs.c        | 68 
> ++++++++++++++++++++++++++++++++++++++
>  xen/include/asm-x86/hvm/vmx/vmcs.h |  1 +
>  2 files changed, 69 insertions(+)
> 
> diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
> index 7bf19a0..e1a8f95 100644
> --- a/xen/arch/x86/hvm/vmx/vmcs.c
> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
> @@ -1465,6 +1465,74 @@ int vmx_add_msr(struct vcpu *v, uint32_t msr, uint64_t 
> val,
>      return rc;
>  }
>  
> +int vmx_del_msr(struct vcpu *v, uint32_t msr, enum vmx_msr_list_type type)
> +{
> +    struct arch_vmx_struct *arch_vmx = &v->arch.hvm_vmx;
> +    struct vmx_msr_entry *start = NULL, *ent, *end;
> +    unsigned int substart, subend, total;
> +
> +    ASSERT(v == current || !vcpu_runnable(v));
> +
> +    switch ( type )
> +    {
> +    case VMX_MSR_HOST:
> +        start    = arch_vmx->host_msr_area;
> +        substart = 0;
> +        subend   = arch_vmx->host_msr_count;
> +        total    = subend;
> +        break;
> +
> +    case VMX_MSR_GUEST:
> +        start    = arch_vmx->msr_area;
> +        substart = 0;
> +        subend   = arch_vmx->msr_save_count;
> +        total    = arch_vmx->msr_load_count;
> +        break;
> +
> +    case VMX_MSR_GUEST_LOADONLY:
> +        start    = arch_vmx->msr_area;
> +        substart = arch_vmx->msr_save_count;
> +        subend   = arch_vmx->msr_load_count;
> +        total    = subend;
> +        break;
> +
> +    default:
> +        ASSERT_UNREACHABLE();
> +    }

The above chunk is already in vmx_find_msr and vmx_add_msr, maybe a
static helper that sets start/substart/subend/total would be helpful
here?

Roger.

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