Re: [Xen-devel] [PATCH v14 07/17] pvh: vmx-specific changes

[Tim Deegan <tim@xxxxxxx>]

At 12:14 +0000 on 04 Nov (1383563696), George Dunlap wrote:
> +    if ( is_pvh_domain(d) )
> +    {
> +        /* Disable virtual apics, TPR */
> +        v->arch.hvm_vmx.secondary_exec_control &= 
> +            ~(SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES
> +              | SECONDARY_EXEC_APIC_REGISTER_VIRT
> +              | SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY);
> +        v->arch.hvm_vmx.exec_control &= ~CPU_BASED_TPR_SHADOW;
> +
> +        /* Disable wbinvd (only necessary for MMIO),
> +         * unrestricted guest (real mode for EPT) */
> +        v->arch.hvm_vmx.secondary_exec_control &= 
> +            ~(SECONDARY_EXEC_UNRESTRICTED_GUEST
> +              | SECONDARY_EXEC_WBINVD_EXITING);

WBINVD exiting is used for supporting _real_ MMIO, which PVH guetst
will still have, right?

> +        if ( is_pvh_domain(d) )
> +            vmx_disable_intercept_for_msr(v, MSR_SHADOW_GS_BASE, MSR_TYPE_R 
> | MSR_TYPE_W);
> +
> +        /*
> +         * PVH: We don't disable intercepts for MSRs: MSR_STAR, MSR_LSTAR,
> +         *      MSR_CSTAR, and MSR_SYSCALL_MASK because we need to specify
> +         *      save/restore area to save/restore at every VM exit and entry.
> +         *      Instead, let the intercept functions save them into
> +         *      vmx_msr_state fields. See comment in vmx_restore_host_msrs().
> +         *      See also vmx_restore_guest_msrs().
> +         */

Why are these MSRs special for PVH guests?  Are PVH guests restricted
in how they can use SHADOW_GS?

Tim.

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