On Feb 22, 2016 04:23, "Razvan Cojocaru" <rcojoc...@bitdefender.com> wrote: > > On 02/19/2016 07:26 PM, Lengyel, Tamas wrote: > > > > > > On Fri, Feb 19, 2016 at 10:18 AM, Andrew Cooper > > <andrew.coop...@citrix.com <mailto:andrew.coop...@citrix.com>> wrote: > > > > On 19/02/16 17:06, Lengyel, Tamas wrote: > >> > >> > >> On Tue, Feb 16, 2016 at 3:47 AM, Jan Beulich <jbeul...@suse.com > >> <mailto:jbeul...@suse.com>> wrote: > >> > >> >>> On 16.02.16 at 07:58, <<mailto:kevin.t...@intel.com> kevin.t...@intel.com > >> <mailto:kevin.t...@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 might have missed that comment. > > > > > > > > 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? > > > > > > Right now only dr7 is included in the automatic register snapshot sent > > with each vm_event. I personally don't use any of them so I can't > > comment on how it would be useful by itself (Razvan?). From my > > perspective the only issue at hand has been that the current way dr7 was > > gathered was incorrect. IMHO if someone needs the other debug registers > > for each vm_event, that change can be introduced in a separate patch. > > Andrew is right, all debug registers are relevant for debug activities. > In fact, I've checked with the introspection engine team, and they no > longer use DR7 at the moment (I don't recall exactly why it has been > requested when I first wrote the patch a few years ago). > > So if nobody minds - and I find it unlikely that anyone would - we can, > for the moment, simply remove DR7 altogether from the registers sent > with the vm_event. Should they become necessary, we should indeed > include all of them in a future patch. >
I would rather not remove it if it's not necessary as it's a change in the vm_event interface. If we do, we would have to bump the version, the user needs to be aware of the change, etc. So while the whole vm_event rework was done partly to allow us to do such changes, I would rather just keep it for now. Tamas
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