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From: Peter Zijlstra <peterz@infradead.org>
To: Tianyu Lan <ltykernel@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
	kys@microsoft.com, haiyangz@microsoft.com,
	sthemmin@microsoft.com, wei.liu@kernel.org, decui@microsoft.com,
	tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com,
	luto@kernel.org, konrad.wilk@oracle.com,
	boris.ostrovsky@oracle.com, jgross@suse.com,
	sstabellini@kernel.org, joro@8bytes.org, will@kernel.org,
	davem@davemloft.net, kuba@kernel.org, jejb@linux.ibm.com,
	martin.petersen@oracle.com, arnd@arndb.de, hch@lst.de,
	m.szyprowski@samsung.com, robin.murphy@arm.com,
	Tianyu.Lan@microsoft.com, rppt@kernel.org,
	kirill.shutemov@linux.intel.com, akpm@linux-foundation.org,
	brijesh.singh@amd.com, thomas.lendacky@amd.com,
	pgonda@google.com, david@redhat.com, krish.sadhukhan@oracle.com,
	saravanand@fb.com, aneesh.kumar@linux.ibm.com,
	xen-devel@lists.xenproject.org, martin.b.radev@gmail.com,
	ardb@kernel.org, rientjes@google.com, tj@kernel.org,
	keescook@chromium.org, michael.h.kelley@microsoft.com,
	iommu@lists.linux-foundation.org, linux-arch@vger.kernel.org,
	linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-scsi@vger.kernel.org, netdev@vger.kernel.org,
	vkuznets@redhat.com, parri.andrea@gmail.com
Subject: Re: [PATCH V2 03/14] x86/set_memory: Add x86_set_memory_enc static call support
Date: Thu, 5 Aug 2021 16:23:41 +0200	[thread overview]
Message-ID: <YQv0bRBUq1N5+jgG@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <942e6fcb-3bdf-9294-d3db-ca311db440d3@gmail.com>

On Thu, Aug 05, 2021 at 10:05:17PM +0800, Tianyu Lan wrote:
>  static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
>  {
> +	return static_call(x86_set_memory_enc)(addr, numpages, enc);
>  }

Hurpmh... So with a bit of 'luck' you get code-gen like:

__set_memory_enc_dec:
	jmp __SCT_x86_set_memory_enc;

set_memory_encrypted:
	mov $1, %rdx
	jmp __set_memory_enc_dec

set_memory_decrypted:
	mov $0, %rdx
	jmp __set_memory_enc_dec


Which, to me, seems exceedingly daft. Best to make all 3 of those
inlines and use EXPORT_STATIC_CALL_TRAMP_GPL(x86_set_memory_enc) or
something.

This is assuming any of this is actually performance critical, based off
of this using static_call() to begin with.

WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Tianyu Lan <ltykernel@gmail.com>
Cc: parri.andrea@gmail.com, linux-hyperv@vger.kernel.org,
	brijesh.singh@amd.com, david@redhat.com, ardb@kernel.org,
	dave.hansen@linux.intel.com, Dave Hansen <dave.hansen@intel.com>,
	hpa@zytor.com, kys@microsoft.com, will@kernel.org,
	boris.ostrovsky@oracle.com, linux-arch@vger.kernel.org,
	wei.liu@kernel.org, sstabellini@kernel.org,
	sthemmin@microsoft.com, xen-devel@lists.xenproject.org,
	linux-scsi@vger.kernel.org, aneesh.kumar@linux.ibm.com,
	x86@kernel.org, decui@microsoft.com, hch@lst.de,
	michael.h.kelley@microsoft.com, mingo@redhat.com,
	pgonda@google.com, rientjes@google.com, kuba@kernel.org,
	jejb@linux.ibm.com, martin.b.radev@gmail.com,
	thomas.lendacky@amd.com, Tianyu.Lan@microsoft.com,
	keescook@chromium.org, arnd@arndb.de, konrad.wilk@oracle.com,
	haiyangz@microsoft.com, bp@alien8.de, luto@kernel.org,
	krish.sadhukhan@oracle.com, tglx@linutronix.de,
	vkuznets@redhat.com, jgross@suse.com, martin.petersen@oracle.com,
	saravanand@fb.com, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	kirill.shutemov@linux.intel.com, tj@kernel.org,
	akpm@linux-foundation.org, robin.murphy@arm.com,
	davem@davemloft.net, rppt@kernel.org
Subject: Re: [PATCH V2 03/14] x86/set_memory: Add x86_set_memory_enc static call support
Date: Thu, 5 Aug 2021 16:23:41 +0200	[thread overview]
Message-ID: <YQv0bRBUq1N5+jgG@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <942e6fcb-3bdf-9294-d3db-ca311db440d3@gmail.com>

On Thu, Aug 05, 2021 at 10:05:17PM +0800, Tianyu Lan wrote:
>  static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
>  {
> +	return static_call(x86_set_memory_enc)(addr, numpages, enc);
>  }

Hurpmh... So with a bit of 'luck' you get code-gen like:

__set_memory_enc_dec:
	jmp __SCT_x86_set_memory_enc;

set_memory_encrypted:
	mov $1, %rdx
	jmp __set_memory_enc_dec

set_memory_decrypted:
	mov $0, %rdx
	jmp __set_memory_enc_dec


Which, to me, seems exceedingly daft. Best to make all 3 of those
inlines and use EXPORT_STATIC_CALL_TRAMP_GPL(x86_set_memory_enc) or
something.

This is assuming any of this is actually performance critical, based off
of this using static_call() to begin with.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  parent reply	other threads:[~2021-08-05 14:23 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-04 18:44 [PATCH V2 00/14] x86/Hyper-V: Add Hyper-V Isolation VM support Tianyu Lan
2021-08-04 18:44 ` Tianyu Lan
2021-08-04 18:44 ` [PATCH V2 01/14] x86/HV: Initialize GHCB page in Isolation VM Tianyu Lan
2021-08-04 18:44   ` Tianyu Lan
2021-08-04 18:44 ` [PATCH V2 02/14] x86/HV: Initialize shared memory boundary in the " Tianyu Lan
2021-08-04 18:44   ` Tianyu Lan
2021-08-04 18:44 ` [PATCH V2 03/14] x86/set_memory: Add x86_set_memory_enc static call support Tianyu Lan
2021-08-04 18:44   ` Tianyu Lan
2021-08-04 19:27   ` Dave Hansen
2021-08-04 19:27     ` Dave Hansen
2021-08-05 14:05     ` Tianyu Lan
2021-08-05 14:05       ` Tianyu Lan
2021-08-05 14:11       ` Peter Zijlstra
2021-08-05 14:11         ` Peter Zijlstra
2021-08-05 14:23       ` Peter Zijlstra [this message]
2021-08-05 14:23         ` Peter Zijlstra
2021-08-05 14:29         ` Dave Hansen
2021-08-05 14:29           ` Dave Hansen
2021-08-05 15:51           ` Tianyu Lan
2021-08-05 15:51             ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 04/14] x86/HV: Add new hvcall guest address host visibility support Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 05/14] HV: Mark vmbus ring buffer visible to host in Isolation VM Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 06/14] HV: Add Write/Read MSR registers via ghcb page Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 07/14] HV: Add ghcb hvcall support for SNP VM Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 08/14] HV/Vmbus: Add SNP support for VMbus channel initiate message Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 09/14] HV/Vmbus: Initialize VMbus ring buffer for Isolation VM Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 10/14] DMA: Add dma_map_decrypted/dma_unmap_encrypted() function Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan
2021-08-05 15:56   ` Tianyu Lan
2021-08-05 15:56     ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 11/14] x86/Swiotlb: Add Swiotlb bounce buffer remap function for HV IVM Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan
2021-08-05 16:01   ` Tianyu Lan
2021-08-05 16:01     ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 12/14] HV/IOMMU: Enable swiotlb bounce buffer for Isolation VM Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 13/14] HV/Netvsc: Add Isolation VM support for netvsc driver Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan
2021-08-04 18:45 ` [PATCH V2 14/14] HV/Storvsc: Add Isolation VM support for storvsc driver Tianyu Lan
2021-08-04 18:45   ` Tianyu Lan

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