linux-kernel - Re: [RFC PATCH v11 12/29] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory

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Message-ID: <29baac45-7736-a28c-3b2d-2a6e45171b8b@intel.com>
Date:   Fri, 21 Jul 2023 23:42:04 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Huacai Chen <chenhuacai@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>
Cc:     kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.linux.dev, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Fuad Tabba <tabba@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Maciej Szmigiero <mail@...iej.szmigiero.name>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>,
        Wang <wei.w.wang@...el.com>,
        Liam Merwick <liam.merwick@...cle.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC PATCH v11 12/29] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for
 guest-specific backing memory

On 7/21/2023 11:05 PM, Xiaoyao Li wrote:
> On 7/19/2023 7:44 AM, Sean Christopherson wrote:
>> @@ -6255,12 +6298,17 @@ int kvm_init(unsigned vcpu_size, unsigned 
>> vcpu_align, struct module *module)
>>       if (r)
>>           goto err_async_pf;
>> +    r = kvm_gmem_init();
>> +    if (r)
>> +        goto err_gmem;
>> +
>>       kvm_chardev_ops.owner = module;
>>       kvm_preempt_ops.sched_in = kvm_sched_in;
>>       kvm_preempt_ops.sched_out = kvm_sched_out;
>>       kvm_init_debug();
>> +    kvm_gmem_init();
> 
> why kvm_gmem_init() needs to be called again? by mistake?

I'm sure it's a mistake.

I'm testing the gmem QEMU with this series. SW_PROTECTED_VM gets stuck 
in a loop in early OVMF code due to two shared page of OVMF get zapped 
and re-mapped infinitely. Removing the second call of kvm_gmem_init() 
can solve the issue, though I'm not sure about the reason.