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From: Tianyu Lan <ltykernel@gmail.com>
To: Michael Kelley <mikelley@microsoft.com>,
	KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	"wei.liu@kernel.org" <wei.liu@kernel.org>,
	Dexuan Cui <decui@microsoft.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"bp@alien8.de" <bp@alien8.de>, "x86@kernel.org" <x86@kernel.org>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
	"luto@kernel.org" <luto@kernel.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
	"boris.ostrovsky@oracle.com" <boris.ostrovsky@oracle.com>,
	"jgross@suse.com" <jgross@suse.com>,
	"sstabellini@kernel.org" <sstabellini@kernel.org>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"will@kernel.org" <will@kernel.org>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"kuba@kernel.org" <kuba@kernel.org>,
	"jejb@linux.ibm.com" <jejb@linux.ibm.com>,
	"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
	"arnd@arndb.de" <arnd@arndb.de>, "hch@lst.de" <hch@lst.de>,
	"m.szyprowski@samsung.com" <m.szyprowski@samsung.com>,
	"robin.murphy@arm.com" <robin.murphy@arm.com>,
	"thomas.lendacky@amd.com" <thomas.lendacky@amd.com>,
	"brijesh.singh@amd.com" <brijesh.singh@amd.com>,
	"ardb@kernel.org" <ardb@kernel.org>,
	Tianyu Lan <Tianyu.Lan@microsoft.com>,
	"pgonda@google.com" <pgonda@google.com>,
	"martin.b.radev@gmail.com" <martin.b.radev@gmail.com>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"kirill.shutemov@linux.intel.com"
	<kirill.shutemov@linux.intel.com>,
	"rppt@kernel.org" <rppt@kernel.org>,
	"sfr@canb.auug.org.au" <sfr@canb.auug.org.au>,
	"saravanand@fb.com" <saravanand@fb.com>,
	"krish.sadhukhan@oracle.com" <krish.sadhukhan@oracle.com>,
	"aneesh.kumar@linux.ibm.com" <aneesh.kumar@linux.ibm.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"rientjes@google.com" <rientjes@google.com>,
	"hannes@cmpxchg.org" <hannes@cmpxchg.org>,
	"tj@kernel.org" <tj@kernel.org>
Cc: "iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	vkuznets <vkuznets@redhat.com>,
	"parri.andrea@gmail.com" <parri.andrea@gmail.com>,
	"dave.hansen@intel.com" <dave.hansen@intel.com>
Subject: Re: [PATCH V3 13/13] HV/Storvsc: Add Isolation VM support for storvsc driver
Date: Sat, 21 Aug 2021 02:04:11 +0800	[thread overview]
Message-ID: <939aa552-5c24-65ee-518d-1cf72867c15d@gmail.com> (raw)
In-Reply-To: <CY4PR21MB158664748760672446BFA075D7C19@CY4PR21MB1586.namprd21.prod.outlook.com>



On 8/21/2021 12:08 AM, Michael Kelley wrote:
>>>>    	}
>>> The whole approach here is to do dma remapping on each individual page
>>> of the I/O buffer.  But wouldn't it be possible to use dma_map_sg() to map
>>> each scatterlist entry as a unit?  Each scatterlist entry describes a range of
>>> physically contiguous memory.  After dma_map_sg(), the resulting dma
>>> address must also refer to a physically contiguous range in the swiotlb
>>> bounce buffer memory.   So at the top of the "for" loop over the scatterlist
>>> entries, do dma_map_sg() if we're in an isolated VM.  Then compute the
>>> hvpfn value based on the dma address instead of sg_page().  But everything
>>> else is the same, and the inner loop for populating the pfn_arry is unmodified.
>>> Furthermore, the dma_range array that you've added is not needed, since
>>> scatterlist entries already have a dma_address field for saving the mapped
>>> address, and dma_unmap_sg() uses that field.
>> I don't use dma_map_sg() here in order to avoid introducing one more
>> loop(e,g dma_map_sg()). We already have a loop to populate
>> cmd_request->dma_range[] and so do the dma map in the same loop.
>>
> I'm not seeing where the additional loop comes from.  Storvsc
> already has a loop through the sgl entries.  Retain that loop and call
> dma_map_sg() with nents set to 1.  Then the sequence is
> dma_map_sg() --> dma_map_sg_attrs() --> dma_direct_map_sg() ->
> dma_direct_map_page().  The latter function will call swiotlb_map()
> to map all pages of the sgl entry as a single operation.

After dma_map_sg(), we still need to go through scatter list again to 
populate payload->rrange.pfn_array. We may just go through the scatter 
list just once if dma_map_sg() accepts a callback and run it during go
through scatter list.

WARNING: multiple messages have this Message-ID (diff)
From: Tianyu Lan <ltykernel@gmail.com>
To: Michael Kelley <mikelley@microsoft.com>,
	KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	"wei.liu@kernel.org" <wei.liu@kernel.org>,
	Dexuan Cui <decui@microsoft.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"bp@alien8.de" <bp@alien8.de>, "x86@kernel.org" <x86@kernel.org>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
	"luto@kernel.org" <luto@kernel.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
	"boris.ostrovsky@oracle.com" <boris.ostrovsky@oracle.com>,
	"jgross@suse.com" <jgross@suse.com>,
	"sstabellini@kernel.org" <sstabellini@kernel.org>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"will@kernel.org" <will@kernel.org>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"kuba@kernel.org" <kuba@kernel.org>,
	"jejb@linux.ibm.com" <jejb@linux.ibm.com>,
	"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
	"arnd@arndb.de" <arnd@arndb.de>, "hch@lst.de" <hch@lst.de>,
	"m.szyprowski@samsung.com" <m.szyprowski@samsung.com>,
	"robin.murphy@arm.com" <robin.murphy@arm.com>,
	"thomas.lendacky@amd.com" <thomas.lendacky@amd.com>,
	"brijesh.singh@amd.com" <brijesh.singh@amd.com>,
	"ardb@kernel.org" <ardb@kernel.org>,
	Tianyu Lan <Tianyu.Lan@microsoft.com>,
	"pgonda@google.com" <pgonda@google.com>,
	"martin.b.radev@gmail.com" <martin.b.radev@gmail.com>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"kirill.shutemov@linux.intel.com"
	<kirill.shutemov@linux.intel.com>,
	"rppt@kernel.org" <rppt@kernel.org>,
	"sfr@canb.auug.org.au" <sfr@canb.auug.org.au>,
	"saravanand@fb.com" <saravanand@fb.com>,
	"krish.sadhukhan@oracle.com" <krish.sadhukhan@oracle.com>,
	"aneesh.kumar@linux.ibm.com" <aneesh.kumar@linux.ibm.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"rientjes@google.com" <rientjes@google.com>,
	"hannes@cmpxchg.org" <hannes@cmpxchg.org>,
	"tj@kernel.org" <tj@kernel.org>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
	"parri.andrea@gmail.com" <parri.andrea@gmail.com>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"dave.hansen@intel.com" <dave.hansen@intel.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	vkuznets <vkuznets@redhat.com>
Subject: Re: [PATCH V3 13/13] HV/Storvsc: Add Isolation VM support for storvsc driver
Date: Sat, 21 Aug 2021 02:04:11 +0800	[thread overview]
Message-ID: <939aa552-5c24-65ee-518d-1cf72867c15d@gmail.com> (raw)
In-Reply-To: <CY4PR21MB158664748760672446BFA075D7C19@CY4PR21MB1586.namprd21.prod.outlook.com>



On 8/21/2021 12:08 AM, Michael Kelley wrote:
>>>>    	}
>>> The whole approach here is to do dma remapping on each individual page
>>> of the I/O buffer.  But wouldn't it be possible to use dma_map_sg() to map
>>> each scatterlist entry as a unit?  Each scatterlist entry describes a range of
>>> physically contiguous memory.  After dma_map_sg(), the resulting dma
>>> address must also refer to a physically contiguous range in the swiotlb
>>> bounce buffer memory.   So at the top of the "for" loop over the scatterlist
>>> entries, do dma_map_sg() if we're in an isolated VM.  Then compute the
>>> hvpfn value based on the dma address instead of sg_page().  But everything
>>> else is the same, and the inner loop for populating the pfn_arry is unmodified.
>>> Furthermore, the dma_range array that you've added is not needed, since
>>> scatterlist entries already have a dma_address field for saving the mapped
>>> address, and dma_unmap_sg() uses that field.
>> I don't use dma_map_sg() here in order to avoid introducing one more
>> loop(e,g dma_map_sg()). We already have a loop to populate
>> cmd_request->dma_range[] and so do the dma map in the same loop.
>>
> I'm not seeing where the additional loop comes from.  Storvsc
> already has a loop through the sgl entries.  Retain that loop and call
> dma_map_sg() with nents set to 1.  Then the sequence is
> dma_map_sg() --> dma_map_sg_attrs() --> dma_direct_map_sg() ->
> dma_direct_map_page().  The latter function will call swiotlb_map()
> to map all pages of the sgl entry as a single operation.

After dma_map_sg(), we still need to go through scatter list again to 
populate payload->rrange.pfn_array. We may just go through the scatter 
list just once if dma_map_sg() accepts a callback and run it during go
through scatter list.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2021-08-20 18:04 UTC|newest]

Thread overview: 128+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-09 17:56 [PATCH V3 00/13] x86/Hyper-V: Add Hyper-V Isolation VM support Tianyu Lan
2021-08-09 17:56 ` Tianyu Lan
2021-08-09 17:56 ` [PATCH V3 01/13] x86/HV: Initialize GHCB page in Isolation VM Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-10 10:56   ` Wei Liu
2021-08-10 10:56     ` Wei Liu
2021-08-10 12:17     ` Tianyu Lan
2021-08-10 12:17       ` Tianyu Lan
2021-08-12 19:14   ` Michael Kelley
2021-08-12 19:14     ` Michael Kelley via iommu
2021-08-13 15:46     ` Tianyu Lan
2021-08-13 15:46       ` Tianyu Lan
2021-08-09 17:56 ` [PATCH V3 02/13] x86/HV: Initialize shared memory boundary in the " Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-12 19:18   ` Michael Kelley
2021-08-12 19:18     ` Michael Kelley via iommu
2021-08-14 13:32     ` Tianyu Lan
2021-08-14 13:32       ` Tianyu Lan
2021-08-09 17:56 ` [PATCH V3 03/13] x86/HV: Add new hvcall guest address host visibility support Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-09 22:12   ` Dave Hansen
2021-08-09 22:12     ` Dave Hansen
2021-08-10 13:09     ` Tianyu Lan
2021-08-10 13:09       ` Tianyu Lan
2021-08-10 11:03   ` Wei Liu
2021-08-10 11:03     ` Wei Liu
2021-08-10 12:25     ` Tianyu Lan
2021-08-10 12:25       ` Tianyu Lan
2021-08-12 19:36   ` Michael Kelley
2021-08-12 19:36     ` Michael Kelley via iommu
2021-08-12 21:10   ` Michael Kelley
2021-08-12 21:10     ` Michael Kelley via iommu
2021-08-09 17:56 ` [PATCH V3 04/13] HV: Mark vmbus ring buffer visible to host in Isolation VM Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-12 22:20   ` Michael Kelley
2021-08-12 22:20     ` Michael Kelley via iommu
2021-08-15 15:21     ` Tianyu Lan
2021-08-15 15:21       ` Tianyu Lan
2021-08-09 17:56 ` [PATCH V3 05/13] HV: Add Write/Read MSR registers via ghcb page Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-13 19:31   ` Michael Kelley
2021-08-13 19:31     ` Michael Kelley via iommu
2021-08-13 20:26     ` Michael Kelley
2021-08-13 20:26       ` Michael Kelley via iommu
2021-08-24  8:45   ` Christoph Hellwig
2021-08-24  8:45     ` Christoph Hellwig
2021-08-09 17:56 ` [PATCH V3 06/13] HV: Add ghcb hvcall support for SNP VM Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-13 20:42   ` Michael Kelley
2021-08-13 20:42     ` Michael Kelley via iommu
2021-08-09 17:56 ` [PATCH V3 07/13] HV/Vmbus: Add SNP support for VMbus channel initiate message Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-13 21:28   ` Michael Kelley
2021-08-13 21:28     ` Michael Kelley via iommu
2021-08-09 17:56 ` [PATCH V3 08/13] HV/Vmbus: Initialize VMbus ring buffer for Isolation VM Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-16 17:28   ` Michael Kelley
2021-08-16 17:28     ` Michael Kelley via iommu
2021-08-17 15:36     ` Tianyu Lan
2021-08-17 15:36       ` Tianyu Lan
2021-08-09 17:56 ` [PATCH V3 09/13] DMA: Add dma_map_decrypted/dma_unmap_encrypted() function Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-12 12:26   ` Christoph Hellwig
2021-08-12 12:26     ` Christoph Hellwig
2021-08-12 15:38     ` Tianyu Lan
2021-08-12 15:38       ` Tianyu Lan
2021-08-09 17:56 ` [PATCH V3 10/13] x86/Swiotlb: Add Swiotlb bounce buffer remap function for HV IVM Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-12 12:27   ` Christoph Hellwig
2021-08-12 12:27     ` Christoph Hellwig
2021-08-13 17:58     ` Tianyu Lan
2021-08-13 17:58       ` Tianyu Lan
2021-08-16 14:50       ` Tianyu Lan
2021-08-16 14:50         ` Tianyu Lan
2021-08-19  8:49         ` Christoph Hellwig
2021-08-19  8:49           ` Christoph Hellwig
2021-08-19  9:59           ` Tianyu Lan
2021-08-19  9:59             ` Tianyu Lan
2021-08-19 10:02             ` Christoph Hellwig
2021-08-19 10:02               ` Christoph Hellwig
2021-08-19 10:03               ` Tianyu Lan
2021-08-19 10:03                 ` Tianyu Lan
2021-08-09 17:56 ` [PATCH V3 11/13] HV/IOMMU: Enable swiotlb bounce buffer for Isolation VM Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-19 18:11   ` Michael Kelley
2021-08-19 18:11     ` Michael Kelley via iommu
2021-08-20  4:13     ` hch
2021-08-20  4:13       ` hch
2021-08-20  9:32     ` Tianyu Lan
2021-08-20  9:32       ` Tianyu Lan
2021-08-09 17:56 ` [PATCH V3 12/13] HV/Netvsc: Add Isolation VM support for netvsc driver Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-19 18:14   ` Michael Kelley
2021-08-19 18:14     ` Michael Kelley via iommu
2021-08-20  4:21     ` hch
2021-08-20  4:21       ` hch
2021-08-20 13:11       ` Tianyu Lan
2021-08-20 13:11         ` Tianyu Lan
2021-08-20 13:30       ` Tom Lendacky
2021-08-20 13:30         ` Tom Lendacky via iommu
2021-08-20 18:20     ` Tianyu Lan
2021-08-20 18:20       ` Tianyu Lan
2021-08-09 17:56 ` [PATCH V3 13/13] HV/Storvsc: Add Isolation VM support for storvsc driver Tianyu Lan
2021-08-09 17:56   ` Tianyu Lan
2021-08-19 18:17   ` Michael Kelley
2021-08-19 18:17     ` Michael Kelley via iommu
2021-08-20  4:32     ` hch
2021-08-20  4:32       ` hch
2021-08-20 15:40       ` Michael Kelley
2021-08-20 15:40         ` Michael Kelley via iommu
2021-08-24  8:49         ` min_align_mask " hch
2021-08-24  8:49           ` hch
2021-08-20 16:01       ` Tianyu Lan
2021-08-20 16:01         ` Tianyu Lan
2021-08-20 15:20     ` Tianyu Lan
2021-08-20 15:20       ` Tianyu Lan
2021-08-20 15:37       ` Tianyu Lan
2021-08-20 15:37         ` Tianyu Lan
2021-08-20 16:08       ` Michael Kelley via iommu
2021-08-20 16:08         ` Michael Kelley
2021-08-20 18:04         ` Tianyu Lan [this message]
2021-08-20 18:04           ` Tianyu Lan
2021-08-20 19:22           ` Michael Kelley
2021-08-20 19:22             ` Michael Kelley via iommu
2021-08-24  8:46           ` hch
2021-08-24  8:46             ` hch
2021-08-16 14:55 ` [PATCH V3 00/13] x86/Hyper-V: Add Hyper-V Isolation VM support Michael Kelley
2021-08-16 14:55   ` Michael Kelley via iommu

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