[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v1 4/6] x86/hvm: Add SMAP support to HVM guest
>>> On 16.04.14 at 10:54, <feng.wu@xxxxxxxxx> wrote: > >> -----Original Message----- >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx] >> Sent: Wednesday, April 16, 2014 4:47 PM >> To: Wu, Feng >> Cc: Ian.Campbell@xxxxxxxxxx; Dong, Eddie; Nakajima, Jun; >> xen-devel@xxxxxxxxxxxxx >> Subject: RE: [PATCH v1 4/6] x86/hvm: Add SMAP support to HVM guest >> >> >>> On 16.04.14 at 03:49, <feng.wu@xxxxxxxxx> wrote: >> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx] >> >> >>> On 15.04.14 at 15:02, <feng.wu@xxxxxxxxx> wrote: >> >> > @@ -371,6 +383,7 @@ static inline int hvm_event_pending(struct vcpu >> *v) >> >> > X86_CR4_MCE | X86_CR4_PGE | X86_CR4_PCE | \ >> >> > X86_CR4_OSFXSR | X86_CR4_OSXMMEXCPT | \ >> >> > (cpu_has_smep ? X86_CR4_SMEP : 0) | \ >> >> > + (hvm_cpuid_has_smap() ? X86_CR4_SMAP : 0) | \ >> >> >> >> What's the reason for the asymmetry with SMEP here? Also, did you >> >> verify that v == current in all call paths? And even if you did, passing >> >> v into the function and adding a respective ASSERT() would seem >> >> rather desirable. >> > >> > My original thought is that "cpu_has_smap" reflects whether the host cpu >> has >> > SMAP feature, however, here we need to check whether the VCPU of the hvm >> > has this feature, so I used hvm_cpuid_has_smap() instead. But I thought >> > about >> > this logic again yesterday, seems using "cpu_has_smap" here is okay, since >> > we >> > always expose the SMAP feature to HVM guest if it exists on the host cpu. > So >> > I will change this to align with smep. >> >> Please indeed do so initially, even if your argumentation is slightly >> wrong: Via CPUID masking the guest may not see the SMEP and/or >> SMAP features, and hence cpu_has_sm[ea]p isn't generally the >> correct qualifier. So we'd need a fixup patch on top (or, alternatively >> one preceding the SMAP additions, correcting the SMEP aspect here, >> in which case then your change could remain as is). >> > > So, I need send out a patch to fix this SMEP issue, then make the SMAP patch > set > based on it, right? That would be the ideal flow, yes. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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