linux-kernel - Re: [PATCH 5/7] x86/mmu: Allocate/free PASID

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Message-ID: <87d07spk8a.fsf@nanos.tec.linutronix.de>
Date:   Tue, 28 Apr 2020 01:44:21 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Jacob Jun Pan <jacob.jun.pan@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Sohil Mehta <sohil.mehta@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        x86 <x86@...nel.org>, iommu@...ts.linux-foundation.org
Subject: Re: [PATCH 5/7] x86/mmu: Allocate/free PASID

Fenghua Yu <fenghua.yu@...el.com> writes:
> On Sun, Apr 26, 2020 at 04:55:25PM +0200, Thomas Gleixner wrote:
>> Fenghua Yu <fenghua.yu@...el.com> writes:
>> > + +#ifdef CONFIG_INTEL_IOMMU_SVM +	int pasid;
>> 
>> int? It's a value which gets programmed into the MSR along with the valid 
>> bit (bit 31) set.
>
> The pasid is defined as "int" in struct intel_svm and in 
> intel_svm_bind_mm() and intel_svm_unbind_mm(). So the pasid defined in this 
> patch follows the same type defined in those places.

Which are wrong to begin with.

>> ioasid_alloc() uses ioasid_t which is
>> 
>> typedef unsigned int ioasid_t;
>> 
>> Can we please have consistent types and behaviour all over the place?
>
> Should I just define "pasid", "pasid_max", "flags" as "unsigned int" for
> the new functions/code?
>
> Or should I also change their types to "unsigned int" in the original
> svm code (struct intel_svm, ...bind_mm(), etc)? I'm afraid that will be
> a lot of changes and should be in a separate preparation patch.

Yes, please. The existance of non-sensical code is not an excuse to
proliferate it.

Thanks,

        tglx