linux-kernel - Re: [RFC KVM 24/27] kvm/isolation: KVM page fault handler

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Date:   Tue, 14 May 2019 00:25:44 +0300
From:   Liran Alon <liran.alon@...cle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Alexandre Chartre <alexandre.chartre@...cle.com>,
        pbonzini@...hat.com, rkrcmar@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, kvm@...r.kernel.org,
        x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        konrad.wilk@...cle.com, jan.setjeeilers@...cle.com,
        jwadams@...gle.com
Subject: Re: [RFC KVM 24/27] kvm/isolation: KVM page fault handler



> On 13 May 2019, at 18:15, Peter Zijlstra <peterz@...radead.org> wrote:
> 
> 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>
>> 
>> +bool (*kvm_page_fault_handler)(struct pt_regs *regs, unsigned long error_code,
>> +			       unsigned long address);
>> +EXPORT_SYMBOL(kvm_page_fault_handler);
> 
> NAK NAK NAK NAK
> 
> 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