linux-kernel - Re: [PATCH v2 07/20] kvm: x86/mmu: Support zapping SPTEs in the TDP MMU

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Message-ID: <6985f630-3b2a-75f5-5b55-bd76cf32f20b@redhat.com>
Date:   Wed, 21 Oct 2020 19:20:15 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Ben Gardon <bgardon@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Cannon Matthews <cannonmatthews@...gle.com>,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Peter Shier <pshier@...gle.com>,
        Peter Feiner <pfeiner@...gle.com>,
        Junaid Shahid <junaids@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Yulei Zhang <yulei.kernel@...il.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>
Subject: Re: [PATCH v2 07/20] kvm: x86/mmu: Support zapping SPTEs in the TDP
 MMU

On 21/10/20 17:02, Yu Zhang wrote:
>>  void kvm_tdp_mmu_free_root(struct kvm *kvm, struct kvm_mmu_page *root)
>>  {
>> +	gfn_t max_gfn = 1ULL << (boot_cpu_data.x86_phys_bits - PAGE_SHIFT);
>> +
> boot_cpu_data.x86_phys_bits is the host address width. Value of the guest's
> may vary. So maybe we should just traverse the memslots and zap the gfn ranges
> in each of them?
> 

It must be smaller than the host value for two-dimensional paging, though.

Paolo