linux-kernel - Re: [RFC Part1 PATCH v3 16/17] X86/KVM: Provide support to create Guest and HV shared per-CPU variables

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Message-ID: <a059fbc9-5eb7-41c9-bcdc-86ae069f21a5@amd.com>
Date:   Mon, 4 Sep 2017 12:47:15 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...e.de>
Cc:     brijesh.singh@....com, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-efi@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Piotr Luc <piotr.luc@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        David Howells <dhowells@...hat.com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Laura Abbott <labbott@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Dave Airlie <airlied@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>
Subject: Re: [RFC Part1 PATCH v3 16/17] X86/KVM: Provide support to create
 Guest and HV shared per-CPU variables


On 9/4/17 12:05 PM, Borislav Petkov wrote:
> On Fri, Sep 01, 2017 at 05:52:13PM -0500, Brijesh Singh wrote:
>>  So far, we have not seen the need for having such functions except
>> this cases. The approach we have right now works just fine and not
>> sure if its worth adding new functions.
> Then put the call to kvm_map_hv_shared_decrypted() into
> kvm_smp_prepare_boot_cpu() to denote that you're executing this whole
> stuff only once during guest init.
>
> Now you're doing additional jumping-through-hoops with that once static
> var just so you can force something which needs to execute only once but
> gets called in a per-CPU path.
>
> See what I mean?

Yes, I see your point. I will address this issue in next rev.


-Brijesh