Re: [PATCH v3 1/2] hvm/vmx: save dr7 during vmx_vmcs_save

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

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On 19/02/16 17:06, Lengyel, Tamas wrote:
>
>
> On Tue, Feb 16, 2016 at 3:47 AM, Jan Beulich <JBeulich@suse.com
> <mailto:JBeulich@suse.com>> wrote:
>
>     >>> On 16.02.16 at 07:58, <kevin.tian@intel.com <mailto:kevin.tian@intel.com>> wrote:
>     >> --- a/xen/arch/x86/hvm/vmx/vmx.c
>     >> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>     >> @@ -490,6 +490,7 @@ static void vmx_vmcs_save(struct vcpu *v,
>     struct hvm_hw_cpu
>     >> *c)
>     >>      __vmread(GUEST_SYSENTER_CS, &c->sysenter_cs);
>     >>      __vmread(GUEST_SYSENTER_ESP, &c->sysenter_esp);
>     >>      __vmread(GUEST_SYSENTER_EIP, &c->sysenter_eip);
>     >> +    __vmread(GUEST_DR7, &c->dr7);
>     >>
>     >
>     > Hi, Tamas, I didn't see the open closed around "v != current", if
>     > I'm not missing some mails... Have you confirmed with Jan that
>     > he is OK with it?
>
>     We didn't really settle on this yet. I'm not heavily opposed to it
>     remaining unconditional for now, but as said in the other replay
>     my fear is that this might later lead to further additions which
>     may then also be of no interest to the main (save/migration)
>     user of this code.
>
>
> Andrew, any comment if this is OK from your perspective?

I specifically suggested the use of vmx_save_dr() to make all debug
state consistent.

I don't see much purpose in being able to introspect just %dr7.  If any
debug related activities are going on, all debug registers are relevant.

Is this not the case?

~Andrew

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