linux-kernel - Re: [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory

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Date:   Thu, 11 Aug 2022 22:58:16 +0530
From:   "Nikunj A. Dadhania" <nikunj@....com>
To:     Chao Peng <chao.p.peng@...ux.intel.com>,
        "Gupta, Pankaj" <pankaj.gupta@....com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        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>,
        Shuah Khan <shuah@...nel.org>, Mike Rapoport <rppt@...nel.org>,
        Steven Price <steven.price@....com>,
        "Maciej S . Szmigiero" <mail@...iej.szmigiero.name>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
        ak@...ux.intel.com, david@...hat.com, aarcange@...hat.com,
        ddutile@...hat.com, dhildenb@...hat.com,
        Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>, mhocko@...e.com,
        Muchun Song <songmuchun@...edance.com>, bharata@....com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        linux-api@...r.kernel.org, linux-doc@...r.kernel.org,
        qemu-devel@...gnu.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM
 guest private memory

On 11/08/22 19:02, Chao Peng wrote:
> On Thu, Aug 11, 2022 at 01:30:06PM +0200, Gupta, Pankaj wrote:
>>

>>>> Test
>>>> ----
>>>> To test the new functionalities of this patch TDX patchset is needed.
>>>> Since TDX patchset has not been merged so I did two kinds of test:
>>>>
>>>> -  Regresion test on kvm/queue (this patchset)
>>>>     Most new code are not covered. Code also in below repo:
>>>>     https://github.com/chao-p/linux/tree/privmem-v7
>>>>
>>>> -  New Funational test on latest TDX code
>>>>     The patch is rebased to latest TDX code and tested the new
>>>>     funcationalities. See below repos:
>>>>     Linux: https://github.com/chao-p/linux/tree/privmem-v7-tdx
>>>>     QEMU: https://github.com/chao-p/qemu/tree/privmem-v7
>>>
>>> While debugging an issue with SEV+UPM, found that fallocate() returns
>>> an error in QEMU which is not handled (EINTR). With the below handling
>>> of EINTR subsequent fallocate() succeeds:
> 
> QEMU code has not well-tested so it's not strange you met problem. But
> from the man page, there is signal was caught for EINTR, do you know
> the signal number?

I haven't check that, but that should be fairly straight forward to get.
I presume that you are referring to signal_pending() in the shmem_fallocate()

> Thanks for you patch but before we change it in QEMU I want to make sure
> it's indeed a QEMU issue (e.g. not a kernel isssue).

As per the manual fallocate() can return EINTR, and this should be handled 
by the user space.

Regards
Nikunj