linux-kernel - Re: [PATCH V3 13/13] HV/Storvsc: Add Isolation VM support for storvsc driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <939aa552-5c24-65ee-518d-1cf72867c15d@gmail.com>
Date:   Sat, 21 Aug 2021 02:04:11 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Michael Kelley <mikelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
        "boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com>,
        "jgross@...e.com" <jgross@...e.com>,
        "sstabellini@...nel.org" <sstabellini@...nel.org>,
        "joro@...tes.org" <joro@...tes.org>,
        "will@...nel.org" <will@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "arnd@...db.de" <arnd@...db.de>, "hch@....de" <hch@....de>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "brijesh.singh@....com" <brijesh.singh@....com>,
        "ardb@...nel.org" <ardb@...nel.org>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "pgonda@...gle.com" <pgonda@...gle.com>,
        "martin.b.radev@...il.com" <martin.b.radev@...il.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "rppt@...nel.org" <rppt@...nel.org>,
        "sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
        "saravanand@...com" <saravanand@...com>,
        "krish.sadhukhan@...cle.com" <krish.sadhukhan@...cle.com>,
        "aneesh.kumar@...ux.ibm.com" <aneesh.kumar@...ux.ibm.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "rientjes@...gle.com" <rientjes@...gle.com>,
        "hannes@...xchg.org" <hannes@...xchg.org>,
        "tj@...nel.org" <tj@...nel.org>
Cc:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        vkuznets <vkuznets@...hat.com>,
        "parri.andrea@...il.com" <parri.andrea@...il.com>,
        "dave.hansen@...el.com" <dave.hansen@...el.com>
Subject: Re: [PATCH V3 13/13] HV/Storvsc: Add Isolation VM support for storvsc
 driver



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.