From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tim Deegan <tim@xen.org>
Subject: Re: RFC: PVH set vcpu info context in vmcs....
Date: Sat, 17 Aug 2013 11:22:20 +0100
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To: Mukesh Rathor <mukesh.rathor@oracle.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>, Keir Fraser <keir.xen@gmail.com>, Jan Beulich <JBeulich@suse.com>
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At 18:37 -0700 on 16 Aug (1376678229), Mukesh Rathor wrote:
> Ok, changed the tools to clear fields, tested and everything works:
> 
> /*
>  * Set vmcs fields during boot of a vcpu. Called from arch_set_info_guest.
>  *
>  * Boot vcpu call is from tools via:
>  *     do_domctl -> XEN_DOMCTL_setvcpucontext -> arch_set_info_guest
>  *
>  * Secondary vcpu's are brought up by the guest itself via:
>  *     do_vcpu_op -> VCPUOP_initialise -> arch_set_info_guest
>  *     (In case of linux, the call comes from cpu_initialize_context()).
>  *
>  * Note, PVH save/restore is expected to happen the HVM way, ie,
>  *        do_domctl -> XEN_DOMCTL_sethvmcontext -> hvm_load/save
>  * and not get here.
>  *
>  * PVH 32bitfixme: this function needs to be modified for 32bit guest.

What's the 32-bit interface going to be like?  Presumably it will have
to load segment state, so this is just postponing that work until then.

>  */
> int vmx_pvh_vcpu_boot_set_info(struct vcpu *v, 
>                                struct vcpu_guest_context *ctxtp)
> {
>     if ( ctxtp->ldt_base || ctxtp->ldt_ents ||
>          ctxtp->user_regs.cs || ctxtp->user_regs.ss || ctxtp->user_regs.es ||
>          ctxtp->user_regs.ds || ctxtp->user_regs.fs || ctxtp->user_regs.gs ||
>          ctxtp->gdt.pvh.addr || ctxtp->gdt.pvh.limit ||
>          ctxtp->fs_base || ctxtp->gs_base_user )
>         return -EINVAL;
> 
>     vmx_vmcs_enter(v);
>     __vmwrite(GUEST_GS_BASE, ctxtp->gs_base_kernel);
>     vmx_vmcs_exit(v);

Why does this one field get loaded?  Couldn't it be zero too?

Tim.