linux-kernel - Re: [PATCH v3 00/15] KVM: mm: fd-based approach for supporting KVM guest private memory

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Date:   Tue, 21 Dec 2021 15:44:40 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Chao Peng <chao.p.peng@...ux.intel.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        qemu-devel@...gnu.org, Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Hugh Dickins <hughd@...gle.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        luto@...nel.org, john.ji@...el.com, susie.li@...el.com,
        jun.nakajima@...el.com, dave.hansen@...el.com, ak@...ux.intel.com,
        david@...hat.com
Subject: Re: [PATCH v3 00/15] KVM: mm: fd-based approach for supporting KVM
 guest private memory

On Tue, Dec 21, 2021, Chao Peng wrote:
> This is the third version of this series which try to implement the
> fd-based KVM guest private memory.

...

> Test
> ----
> This code has been tested with latest TDX code patches hosted at
> (https://github.com/intel/tdx/tree/kvm-upstream) with minimal TDX
> adaption and QEMU support.
> 
> Example QEMU command line:
> -object tdx-guest,id=tdx \
> -object memory-backend-memfd-private,id=ram1,size=2G \
> -machine q35,kvm-type=tdx,pic=no,kernel_irqchip=split,memory-encryption=tdx,memory-backend=ram1
> 
> Changelog
> ----------
> v3:
>   - Added locking protection when calling
>     invalidate_page_range/fallocate callbacks.
>   - Changed memslot structure to keep use useraddr for shared memory.
>   - Re-organized F_SEAL_INACCESSIBLE and MEMFD_OPS.
>   - Added MFD_INACCESSIBLE flag to force F_SEAL_INACCESSIBLE.
>   - Commit message improvement.
>   - Many small fixes for comments from the last version.

Can you rebase on top of kvm/queue and send a new version?  There's a massive
overhaul of KVM's memslots code that's queued for 5.17, and the KVM core changes
in this series conflict mightily.

It's ok if the private memslot support isn't tested exactly as-is, it's not like
any of us reviewers can test it anyways, but I would like to be able to apply
cleanly and verify that the series doesn't break existing functionality.

This version also appears to be based on an internal development branch, e.g. patch
12/15 has some bits from the TDX series.

@@ -336,6 +348,7 @@ struct kvm_tdx_exit {
 #define KVM_EXIT_X86_BUS_LOCK     33
 #define KVM_EXIT_XEN              34
 #define KVM_EXIT_RISCV_SBI        35
+#define KVM_EXIT_MEMORY_ERROR     36
 #define KVM_EXIT_TDX              50   /* dump number to avoid conflict. */

 /* For KVM_EXIT_INTERNAL_ERROR */
@@ -554,6 +567,8 @@ struct kvm_run {
                        unsigned long args[6];
                        unsigned long ret[2];
                } riscv_sbi;
+               /* KVM_EXIT_MEMORY_ERROR */
+               struct kvm_memory_exit mem;
                /* KVM_EXIT_TDX_VMCALL */
                struct kvm_tdx_exit tdx;
                /* Fix the size of the union. */