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From: Borislav Petkov <bp@alien8.de>
To: "Luck, Tony" <tony.luck@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Fenghua Yu <fenghua.yu@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Joerg Roedel <joro@8bytes.org>, Ingo Molnar <mingo@redhat.com>,
	H Peter Anvin <hpa@zytor.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Christoph Hellwig <hch@infradeed.org>,
	Ashok Raj <ashok.raj@intel.com>,
	Jacob Jun Pan <jacob.jun.pan@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Sohil Mehta <sohil.mehta@intel.com>,
	Ravi V Shankar <ravi.v.shankar@intel.com>,
	linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>,
	iommu@lists.linux-foundation.org
Subject: Re: [PATCH v4 12/12] x86/traps: Fix up invalid PASID
Date: Fri, 26 Jun 2020 20:15:50 +0200	[thread overview]
Message-ID: <20200626181550.GF27151@zn.tnic> (raw)
In-Reply-To: <20200626181000.GA22833@agluck-desk2.amr.corp.intel.com>

On Fri, Jun 26, 2020 at 11:10:00AM -0700, Luck, Tony wrote:
> Do we have a standard way of coding for a feature that depends on multiple
> other features?  For this case the system needs to both suport the ENQCMD
> instruction, and also have kernel code that programs the IOMMU.

Yes, you need both. Consider distros enabling everything so that they
can ship a single kernel image.

> And/or guidance on when to use each of the very somewhat simlar looking
> 	boot_cpu_has()
> 	static_cpu_has()

See the comment over _static_cpu_has() in arch/x86/include/asm/cpufeature.h

In the exception path you should use the static_ variant.

> 	IS_ENABLED()

This is testing CONFIG_ settings, i.e., build time.

> 	cpu_feature_enabled()

This too, indirectly. See

arch/x86/include/asm/disabled-features.h

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

WARNING: multiple messages have this Message-ID (diff)
From: Borislav Petkov <bp@alien8.de>
To: "Luck, Tony" <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	Ravi V Shankar <ravi.v.shankar@intel.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Peter Zijlstra <peterz@infradead.org>, x86 <x86@kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Dave Hansen <dave.hansen@intel.com>,
	iommu@lists.linux-foundation.org, Ingo Molnar <mingo@redhat.com>,
	Christoph Hellwig <hch@infradeed.org>,
	Jacob Jun Pan <jacob.jun.pan@intel.com>,
	H Peter Anvin <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v4 12/12] x86/traps: Fix up invalid PASID
Date: Fri, 26 Jun 2020 20:15:50 +0200	[thread overview]
Message-ID: <20200626181550.GF27151@zn.tnic> (raw)
In-Reply-To: <20200626181000.GA22833@agluck-desk2.amr.corp.intel.com>

On Fri, Jun 26, 2020 at 11:10:00AM -0700, Luck, Tony wrote:
> Do we have a standard way of coding for a feature that depends on multiple
> other features?  For this case the system needs to both suport the ENQCMD
> instruction, and also have kernel code that programs the IOMMU.

Yes, you need both. Consider distros enabling everything so that they
can ship a single kernel image.

> And/or guidance on when to use each of the very somewhat simlar looking
> 	boot_cpu_has()
> 	static_cpu_has()

See the comment over _static_cpu_has() in arch/x86/include/asm/cpufeature.h

In the exception path you should use the static_ variant.

> 	IS_ENABLED()

This is testing CONFIG_ settings, i.e., build time.

> 	cpu_feature_enabled()

This too, indirectly. See

arch/x86/include/asm/disabled-features.h

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2020-06-26 18:16 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-25 20:17 [PATCH v4 00/12] x86: tag application address space for devices Fenghua Yu
2020-06-25 20:17 ` Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 01/12] iommu: Change type of pasid to u32 Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-26  1:13   ` Lu Baolu
2020-06-26  1:13     ` Lu Baolu
2020-06-25 20:17 ` [PATCH v4 02/12] iommu/vt-d: Change flags type to unsigned int in binding mm Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-26  1:14   ` Lu Baolu
2020-06-26  1:14     ` Lu Baolu
2020-06-25 20:17 ` [PATCH v4 03/12] docs: x86: Add documentation for SVA (Shared Virtual Addressing) Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 04/12] x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 05/12] x86/fpu/xstate: Add supervisor PASID state for ENQCMD feature Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 06/12] x86/msr-index: Define IA32_PASID MSR Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 07/12] mm: Define pasid in mm Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 08/12] fork: Clear PASID for new mm Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 09/12] x86/process: Clear PASID state for a newly forked/cloned thread Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 10/12] x86/mmu: Allocate/free PASID Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-26  1:42   ` Lu Baolu
2020-06-26  1:42     ` Lu Baolu
2020-06-25 20:17 ` [PATCH v4 11/12] sched: Define and initialize a flag to identify valid PASID in the task Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-25 20:17 ` [PATCH v4 12/12] x86/traps: Fix up invalid PASID Fenghua Yu
2020-06-25 20:17   ` Fenghua Yu
2020-06-26  1:46   ` Lu Baolu
2020-06-26  1:46     ` Lu Baolu
2020-06-26  9:44   ` Peter Zijlstra
2020-06-26  9:44     ` Peter Zijlstra
2020-06-26 18:10     ` Luck, Tony
2020-06-26 18:10       ` Luck, Tony
2020-06-26 18:15       ` Borislav Petkov [this message]
2020-06-26 18:15         ` Borislav Petkov
2020-06-26 18:23       ` Dave Hansen
2020-06-26 18:23         ` Dave Hansen
2020-06-26 18:35         ` Fenghua Yu
2020-06-26 18:35           ` Fenghua Yu
2020-06-26 18:16     ` Fenghua Yu
2020-06-26 18:16       ` Fenghua Yu

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