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Subject: Re: [RFC KVM 24/27] kvm/isolation: KVM page fault handler
From:   Andy Lutomirski <luto@amacapital.net>
In-Reply-To: <95f462d4-37d3-f863-b7c6-2bcbb92251ec@oracle.com>
Date:   Tue, 14 May 2019 08:43:44 -0700
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Liran Alon <liran.alon@oracle.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim Krcmar <rkrcmar@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        kvm list <kvm@vger.kernel.org>, X86 ML <x86@kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        jan.setjeeilers@oracle.com, Jonathan Adams <jwadams@google.com>
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Message-Id: <8DBEACE9-AB4C-4891-8522-A474CA59E325@amacapital.net>
References: <1557758315-12667-1-git-send-email-alexandre.chartre@oracle.com> <1557758315-12667-25-git-send-email-alexandre.chartre@oracle.com> <20190513151500.GY2589@hirez.programming.kicks-ass.net> <13F2FA4F-116F-40C6-9472-A1DE689FE061@oracle.com> <CALCETrUcR=3nfOtFW2qt3zaa7CnNJWJLqRY8AS9FTJVHErjhfg@mail.gmail.com> <20190514072110.GF2589@hirez.programming.kicks-ass.net> <95f462d4-37d3-f863-b7c6-2bcbb92251ec@oracle.com>
To:     Alexandre Chartre <alexandre.chartre@oracle.com>
Sender: linux-kernel-owner@vger.kernel.org
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> On May 14, 2019, at 8:36 AM, Alexandre Chartre <alexandre.chartre@oracle.c=
om> wrote:
>=20
>=20
>> On 5/14/19 9:21 AM, Peter Zijlstra wrote:
>>> On Mon, May 13, 2019 at 07:02:30PM -0700, Andy Lutomirski wrote:
>>> This sounds like a great use case for static_call().  PeterZ, do you
>>> suppose we could wire up static_call() with the module infrastructure
>>> to make it easy to do "static_call to such-and-such GPL module symbol
>>> if that symbol is in a loaded module, else nop"?
>> You're basically asking it to do dynamic linking. And I suppose that is
>> technically possible.
>> However, I'm really starting to think kvm (or at least these parts of it
>> that want to play these games) had better not be a module anymore.
>=20
> Maybe we can use an atomic notifier (e.g. page_fault_notifier)?
>=20
>=20

IMO that=E2=80=99s worse. I want to be able to read do_page_fault() and unde=
rstand what happens and in what order.

Having do_page_fault run with the wrong CR3 is so fundamental to its operati=
on that it needs to be very obvious what=E2=80=99s happening.=