Messages in this thread | | | Subject | Re: [PATCH v3 2/5] KVM: MMU: check guest CR3 reserved bits based on its physical address width. | From | Yu Zhang <> | Date | Thu, 24 Aug 2017 23:38:23 +0800 |
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On 8/24/2017 11:50 PM, Paolo Bonzini wrote: > On 24/08/2017 17:23, Yu Zhang wrote: >>>> static inline u64 rsvd_bits(int s, int e) >>>> { >>>> + if (e < s) >>>> + return 0; >>>> + >>>> return ((1ULL << (e - s + 1)) - 1) << s; >>>> } >>> e = s - 1 is already supported; why do you need e <= s - 2? >> Sorry? I do not quite understand. When will e = s - 1? > Is there any case where e < s? I can see that MAXPHYADDR=63 gives > rsvd_bits(63, 62), but that works. > > In practice, MAXPHYADDR will never be 59 even because the PKRU bits are > at bits 59..62.
Thanks, Paolo. I see. I had made an assumption that MAXPHYADDR shall not exceed the physical one, which is 52 I believe. But I'm not sure there's any place to check this. Maybe we should make sure the vcpu->arch.maxphyaddr will not be greater than the value of the host?
Yu > > Paolo >
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