Re: [PATCH v3 6/6] x86/msr: handle VMX MSRs with guest_rd/wrmsr()

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 13/10/17 13:35, Sergey Dyasli wrote:
> diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
> index a22e3dfaf2..2527fdd1d1 100644
> --- a/xen/arch/x86/msr.c
> +++ b/xen/arch/x86/msr.c
> @@ -426,6 +426,13 @@ int init_vcpu_msr_policy(struct vcpu *v)
>      return 0;
>  }
>  
> +#define vmx_guest_rdmsr(dp, name, msr)     \
> +    case name:                             \
> +        if ( !dp->msr.available )          \
> +            goto gp_fault;                 \
> +        *val = dp->msr.u.raw;              \
> +        break;

Eww :(

For blocks of MSRs, it would be far better to go with the same structure
as the cpuid policy.  Something like:

struct {
    union {
        uint64_t raw[NR_VMX_MSRS];
        struct {
            struct {
                ...
            } basic;
            struct {
                ...
            } pinbased_ctls;
        };
    };
} vmx;

This way, the guest_rdmsr() will be far more efficient.

case MSR_IA32_VMX_BASIC ... xxx:
    if ( !cpuid->basic.vmx )
        goto gp_fault;
    *val = dp->vmx.raw[msr - MSR_IA32_VMX_BASIC];
    break;

It would probably be worth splitting into a couple of different blocks
based on the different availability checks.

~Andrew

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