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Subject: Re: [RFC KVM 24/27] kvm/isolation: KVM page fault handler
From:   Liran Alon <liran.alon@oracle.com>
In-Reply-To: <20190513151500.GY2589@hirez.programming.kicks-ass.net>
Date:   Tue, 14 May 2019 00:25:44 +0300
Cc:     Alexandre Chartre <alexandre.chartre@oracle.com>,
        pbonzini@redhat.com, rkrcmar@redhat.com, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
        dave.hansen@linux.intel.com, luto@kernel.org, kvm@vger.kernel.org,
        x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        konrad.wilk@oracle.com, jan.setjeeilers@oracle.com,
        jwadams@google.com
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References: <1557758315-12667-1-git-send-email-alexandre.chartre@oracle.com>
 <1557758315-12667-25-git-send-email-alexandre.chartre@oracle.com>
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To:     Peter Zijlstra <peterz@infradead.org>
Sender: linux-kernel-owner@vger.kernel.org
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> On 13 May 2019, at 18:15, Peter Zijlstra <peterz@infradead.org> wrote:
>=20
> On Mon, May 13, 2019 at 04:38:32PM +0200, Alexandre Chartre wrote:
>> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
>> index 46df4c6..317e105 100644
>> --- a/arch/x86/mm/fault.c
>> +++ b/arch/x86/mm/fault.c
>> @@ -33,6 +33,10 @@
>> #define CREATE_TRACE_POINTS
>> #include <asm/trace/exceptions.h>
>>=20
>> +bool (*kvm_page_fault_handler)(struct pt_regs *regs, unsigned long =
error_code,
>> +			       unsigned long address);
>> +EXPORT_SYMBOL(kvm_page_fault_handler);
>=20
> NAK NAK NAK NAK
>=20
> This is one of the biggest anti-patterns around.

I agree.
I think that mm should expose a mm_set_kvm_page_fault_handler() or =
something (give it a better name).
Similar to how arch/x86/kernel/irq.c have =
kvm_set_posted_intr_wakeup_handler().

-Liran