[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/4] x86/vmx: Don't leak host syscall MSR state into HVM guests
>>> On 14.02.17 at 09:40, <kevin.tian@xxxxxxxxx> wrote: >> From: Andrew Cooper [mailto:amc96@xxxxxxxxxxxxxxxx] On Behalf Of Andrew >> Cooper >> Sent: Tuesday, February 14, 2017 4:19 PM >> >> On 14/02/2017 08:04, Tian, Kevin wrote: >> >> From: Andrew Cooper [mailto:amc96@xxxxxxxxxxxxxxxx] On Behalf Of Andrew >> Cooper >> >> Sent: Tuesday, February 14, 2017 3:59 PM >> >> >> >> On 14/02/2017 02:52, Tian, Kevin wrote: >> >>>> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx] >> >>>> Sent: Monday, February 13, 2017 10:32 PM >> >>>> >> >>>> hvm_hw_cpu->msr_flags is in fact the VMX dirty bitmap of MSRs needing >> >>>> to be >> >>>> restored when switching into guest context. It should never have been >> >>>> part of >> >>>> the migration state to start with, and Xen must not make any decisions >> >>>> based >> >>>> on the value seen during restore. >> >>>> >> >>>> Identify it as obsolete in the header files, consistently save it as >> >>>> zero and >> >>>> ignore it on restore. >> >>>> >> >>>> The MSRs must be considered dirty during VMCS creation to cause the >> >>>> proper >> >>>> defaults of 0 to be visible to the guest. >> >>>> >> >>>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> >> >>> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>, with one small comment. >> >>> >> >>> the effect of this patch should be more than not leaking syscall MSR. >> >>> what about making the subject clearer when check-in? >> >> What other effects do you think are going on here? Yes, we now context >> >> switch the MSRs right from the start of the domain, but that is >> >> necessary to avoid leaking them. >> >> >> > If just looking at this patch, it's for general MSR save/restore policy, >> > nothing specific to syscall MSR. >> >> The only three MSRs which use this infrastructure are LSTAR, STAR and >> FMASK. What if I were to clarify that in the first paragraph? > > I meant the subject line (talk about syscall MSR leakage) mismatches the > commit message (for general MSR load) I'm with Andrew here: The title seems perfectly fine to me, considering that the generic mechanism is only used for the syscall MSRs. Hence I would think his offer to clarify the change in the first paragraph of the commit message ought to suffice. Otherwise, may I ask that you make a concrete suggestion as to what you'd like to see? Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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