linux-kernel - RE: [PATCH Part2 v6 26/49] KVM: SVM: Add KVM_SEV_SNP_LAUNCH

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Date:   Wed, 29 Jun 2022 18:14:05 +0000
From:   "Kalra, Ashish" <Ashish.Kalra@....com>
To:     Peter Gonda <pgonda@...gle.com>
CC:     the arch/x86 maintainers <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        "Roth, Michael" <Michael.Roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>, Marc Orr <marcorr@...gle.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Alper Gun <alpergun@...gle.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        "jarkko@...nel.org" <jarkko@...nel.org>
Subject: RE: [PATCH Part2 v6 26/49] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_UPDATE
 command

[Public]

>> +static inline void snp_leak_pages(u64 pfn, enum pg_level level) {
>> +       unsigned int npages = page_level_size(level) >> PAGE_SHIFT;
>> +
>> +       WARN(1, "psc failed pfn 0x%llx pages %d (leaking)\n", pfn, 
>> + npages);
>> +
>> +       while (npages) {
>> +               memory_failure(pfn, 0);
>> +               dump_rmpentry(pfn);
>> +               npages--;
>> +               pfn++;
>> +       }
>> +}

>Should this be deduplicated with the snp_leak_pages() in "crypto: ccp:
>Handle the legacy TMR allocation when SNP is enabled" ?

Yes, probably should.

>> +static bool is_hva_registered(struct kvm *kvm, hva_t hva, size_t len) 
>> +{
>> +       struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
>> +       struct list_head *head = &sev->regions_list;
>> +       struct enc_region *i;
>> +
>> +       lockdep_assert_held(&kvm->lock);
>> +
>> +       list_for_each_entry(i, head, list) {
>> +               u64 start = i->uaddr;
>> +               u64 end = start + i->size;
>> +
>> +               if (start <= hva && end >= (hva + len))
>> +                       return true;
>> +       }

>Given that usersapce could load sev->regions_list with any # of any sized regions. Should we add a  cond_resched() like in sev_vm_destroy()?

Actually, is_hva_registered() is also called from PSC handler with kvm->lock mutex held. Even though it is a mutex, I am not really sure if
it is a good idea to do cond_resched() with the kvm->lock mutex held ?

>> +e_unpin:
>> +       /* Content of memory is updated, mark pages dirty */
>> +       for (i = 0; i < n; i++) {

>Since |n| is not only a loop variable but actually carries the number of private pages over to e_unpin can we use a more descriptive name?
>How about something like 'nprivate_pages'?

Yes.

Thanks,
Ashish