From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Woodhouse Subject: Re: [PATCH v1 2/2] dma-mapping-common: add DMA attribute - DMA_ATTR_IOMMU_BYPASS Date: Thu, 29 Oct 2015 22:35:25 +0000 Message-ID: <1446158125.4471.5.camel@infradead.org> References: <1445789224-28032-1-git-send-email-shamir.rabinovitch@oracle.com> <1445789224-28032-2-git-send-email-shamir.rabinovitch@oracle.com> <1446013801.3405.183.camel@infradead.org> <20151028111049.GA30785@shamir-ThinkPad-T430> <1446039110.3405.212.camel@infradead.org> <1446078721.1856.49.camel@kernel.crashing.org> <1446079332.3405.273.camel@infradead.org> <1446081046.1856.55.camel@kernel.crashing.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="sha-1"; protocol="application/x-pkcs7-signature"; boundary="=-z+lA5ddzQUzAJBFdv6vn" Return-path: In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-Archive: List-Post: To: Andy Lutomirski , Benjamin Herrenschmidt Cc: Christian Borntraeger , linux-arch , Paolo Bonzini , Shamir Rabinovitch , Martin Schwidefsky , "linux-doc@vger.kernel.org" , Sebastian Ott , linux-s390 , Cornelia Huck , Joerg Roedel , Jonathan Corbet , KVM , Arnd Bergmann , Christoph Hellwig List-ID: --=-z+lA5ddzQUzAJBFdv6vn Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2015-10-29 at 11:31 -0700, Andy Lutomirski wrote: > On Oct 28, 2015 6:11 PM, "Benjamin Herrenschmidt" > wrote: > >=20 > > On Thu, 2015-10-29 at 09:42 +0900, David Woodhouse wrote: > > > On Thu, 2015-10-29 at 09:32 +0900, Benjamin Herrenschmidt wrote: > > >=20 > > > > On Power, I generally have 2 IOMMU windows for a device, one at > > > > the > > > > bottom is remapped, and is generally used for 32-bit devices > > > > and the > > > > one at the top us setup as a bypass > > >=20 > > > So in the normal case of decent 64-bit devices (and not in a VM), > > > they'll *already* be using the bypass region and have full access > > > to > > > all of memory, all of the time? And you have no protection > > > against > > > driver and firmware bugs causing stray DMA? > >=20 > > Correct, we chose to do that for performance reasons. >=20 > Could this be mitigated using pools? I don't know if the net code > would play along easily. For the receive side, it shouldn't be beyond the wit of man to introduce an API which allocates *and* DMA-maps a skb. Pass it to netif_rx() still mapped, with a destructor that just shoves it back in a pool for re-use. Doing it for transmit might be a little more complex, but perhaps still possible. --=20 dwmw2 --=-z+lA5ddzQUzAJBFdv6vn Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIISjjCCBicw ggUPoAMCAQICAw3vNzANBgkqhkiG9w0BAQUFADCBjDELMAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0 YXJ0Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNpZ25pbmcx ODA2BgNVBAMTL1N0YXJ0Q29tIENsYXNzIDEgUHJpbWFyeSBJbnRlcm1lZGlhdGUgQ2xpZW50IENB MB4XDTE1MDUwNTA5NDM0MVoXDTE2MDUwNTA5NTMzNlowQjEcMBoGA1UEAwwTZHdtdzJAaW5mcmFk ZWFkLm9yZzEiMCAGCSqGSIb3DQEJARYTZHdtdzJAaW5mcmFkZWFkLm9yZzCCASIwDQYJKoZIhvcN AQEBBQADggEPADCCAQoCggEBAMkbm9kPbx1j/X4RVyf/pPKSYwelcco69TvnQQbKM8m8xkWjXJI1 jpJ1jMaGUZGFToINMSZi7lZawUozudWbXSKy1SikENSTJHffsdRAIlsp+hR8vWvjsKUry6sEdqPG doa5RY7+N4WRusWZDYW/RRWE6i9EL9qV86CVPYqw22UBOUw4/j/HVGCV6TSB8yE5iEwhk/hUuzRr FZm1MJMR7mCS7BCR8Lr5jFY61lWpBiXNXIxLZCvDc26KR5L5tYX43iUVO3fzES1GRVoYnxxk2tmz fcsZG5vK+Trc9L8OZJfkYrEHH3+Iw41MQ0w/djVtYr1+HYldx0QmYXAtnhIj+UMCAwEAAaOCAtkw ggLVMAkGA1UdEwQCMAAwCwYDVR0PBAQDAgSwMB0GA1UdJQQWMBQGCCsGAQUFBwMCBggrBgEFBQcD BDAdBgNVHQ4EFgQUszC96C3w5/2+d+atSr0IpT26YI4wHwYDVR0jBBgwFoAUU3Ltkpzg2ssBXHx+ ljVO8tS4UYIwHgYDVR0RBBcwFYETZHdtdzJAaW5mcmFkZWFkLm9yZzCCAUwGA1UdIASCAUMwggE/ MIIBOwYLKwYBBAGBtTcBAgMwggEqMC4GCCsGAQUFBwIBFiJodHRwOi8vd3d3LnN0YXJ0c3NsLmNv bS9wb2xpY3kucGRmMIH3BggrBgEFBQcCAjCB6jAnFiBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1 dGhvcml0eTADAgEBGoG+VGhpcyBjZXJ0aWZpY2F0ZSB3YXMgaXNzdWVkIGFjY29yZGluZyB0byB0 aGUgQ2xhc3MgMSBWYWxpZGF0aW9uIHJlcXVpcmVtZW50cyBvZiB0aGUgU3RhcnRDb20gQ0EgcG9s aWN5LCByZWxpYW5jZSBvbmx5IGZvciB0aGUgaW50ZW5kZWQgcHVycG9zZSBpbiBjb21wbGlhbmNl IG9mIHRoZSByZWx5aW5nIHBhcnR5IG9ibGlnYXRpb25zLjA2BgNVHR8ELzAtMCugKaAnhiVodHRw Oi8vY3JsLnN0YXJ0c3NsLmNvbS9jcnR1MS1jcmwuY3JsMIGOBggrBgEFBQcBAQSBgTB/MDkGCCsG AQUFBzABhi1odHRwOi8vb2NzcC5zdGFydHNzbC5jb20vc3ViL2NsYXNzMS9jbGllbnQvY2EwQgYI KwYBBQUHMAKGNmh0dHA6Ly9haWEuc3RhcnRzc2wuY29tL2NlcnRzL3N1Yi5jbGFzczEuY2xpZW50 LmNhLmNydDAjBgNVHRIEHDAahhhodHRwOi8vd3d3LnN0YXJ0c3NsLmNvbS8wDQYJKoZIhvcNAQEF BQADggEBAHMQmxHHodpS85X8HRyxhvfkys7r+taCNOaNU9cxQu/cZ/6k5nS2qGNMzZ6jb7ueY/V7 7p+4DW/9ZWODDTf4Fz00mh5SSVc20Bz7t+hhxwHd62PZgENh5i76Qq2tw48U8AsYo5damHby1epf neZafLpUkLLO7AGBJIiRVTevdvyXQ0qnixOmKMWyvrhSNGuVIKVdeqLP+102Dwf+dpFyw+j1hz28 jEEKpHa+NR1b2kXuSPi/rMGhexwlJOh4tK8KQ6Ryr0rIN//NSbOgbyYZrzc/ZUWX9V5OA84ChFb2 vkFl0OcYrttp/rhDBLITwffPxSZeoBh9H7zYzkbCXKL3BUIwggYnMIIFD6ADAgECAgMN7zcwDQYJ KoZIhvcNAQEFBQAwgYwxCzAJBgNVBAYTAklMMRYwFAYDVQQKEw1TdGFydENvbSBMdGQuMSswKQYD VQQLEyJTZWN1cmUgRGlnaXRhbCBDZXJ0aWZpY2F0ZSBTaWduaW5nMTgwNgYDVQQDEy9TdGFydENv bSBDbGFzcyAxIFByaW1hcnkgSW50ZXJtZWRpYXRlIENsaWVudCBDQTAeFw0xNTA1MDUwOTQzNDFa Fw0xNjA1MDUwOTUzMzZaMEIxHDAaBgNVBAMME2R3bXcyQGluZnJhZGVhZC5vcmcxIjAgBgkqhkiG 9w0BCQEWE2R3bXcyQGluZnJhZGVhZC5vcmcwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIB AQDJG5vZD28dY/1+EVcn/6TykmMHpXHKOvU750EGyjPJvMZFo1ySNY6SdYzGhlGRhU6CDTEmYu5W WsFKM7nVm10istUopBDUkyR337HUQCJbKfoUfL1r47ClK8urBHajxnaGuUWO/jeFkbrFmQ2Fv0UV hOovRC/alfOglT2KsNtlATlMOP4/x1Rglek0gfMhOYhMIZP4VLs0axWZtTCTEe5gkuwQkfC6+YxW OtZVqQYlzVyMS2Qrw3NuikeS+bWF+N4lFTt38xEtRkVaGJ8cZNrZs33LGRubyvk63PS/DmSX5GKx Bx9/iMONTENMP3Y1bWK9fh2JXcdEJmFwLZ4SI/lDAgMBAAGjggLZMIIC1TAJBgNVHRMEAjAAMAsG A1UdDwQEAwIEsDAdBgNVHSUEFjAUBggrBgEFBQcDAgYIKwYBBQUHAwQwHQYDVR0OBBYEFLMwvegt 8Of9vnfmrUq9CKU9umCOMB8GA1UdIwQYMBaAFFNy7ZKc4NrLAVx8fpY1TvLUuFGCMB4GA1UdEQQX MBWBE2R3bXcyQGluZnJhZGVhZC5vcmcwggFMBgNVHSAEggFDMIIBPzCCATsGCysGAQQBgbU3AQID MIIBKjAuBggrBgEFBQcCARYiaHR0cDovL3d3dy5zdGFydHNzbC5jb20vcG9saWN5LnBkZjCB9wYI KwYBBQUHAgIwgeowJxYgU3RhcnRDb20gQ2VydGlmaWNhdGlvbiBBdXRob3JpdHkwAwIBARqBvlRo aXMgY2VydGlmaWNhdGUgd2FzIGlzc3VlZCBhY2NvcmRpbmcgdG8gdGhlIENsYXNzIDEgVmFsaWRh dGlvbiByZXF1aXJlbWVudHMgb2YgdGhlIFN0YXJ0Q29tIENBIHBvbGljeSwgcmVsaWFuY2Ugb25s eSBmb3IgdGhlIGludGVuZGVkIHB1cnBvc2UgaW4gY29tcGxpYW5jZSBvZiB0aGUgcmVseWluZyBw YXJ0eSBvYmxpZ2F0aW9ucy4wNgYDVR0fBC8wLTAroCmgJ4YlaHR0cDovL2NybC5zdGFydHNzbC5j b20vY3J0dTEtY3JsLmNybDCBjgYIKwYBBQUHAQEEgYEwfzA5BggrBgEFBQcwAYYtaHR0cDovL29j c3Auc3RhcnRzc2wuY29tL3N1Yi9jbGFzczEvY2xpZW50L2NhMEIGCCsGAQUFBzAChjZodHRwOi8v YWlhLnN0YXJ0c3NsLmNvbS9jZXJ0cy9zdWIuY2xhc3MxLmNsaWVudC5jYS5jcnQwIwYDVR0SBBww GoYYaHR0cDovL3d3dy5zdGFydHNzbC5jb20vMA0GCSqGSIb3DQEBBQUAA4IBAQBzEJsRx6HaUvOV /B0csYb35MrO6/rWgjTmjVPXMULv3Gf+pOZ0tqhjTM2eo2+7nmP1e+6fuA1v/WVjgw03+Bc9NJoe UklXNtAc+7foYccB3etj2YBDYeYu+kKtrcOPFPALGKOXWph28tXqX53mWny6VJCyzuwBgSSIkVU3 r3b8l0NKp4sTpijFsr64UjRrlSClXXqiz/tdNg8H/naRcsPo9Yc9vIxBCqR2vjUdW9pF7kj4v6zB oXscJSToeLSvCkOkcq9KyDf/zUmzoG8mGa83P2VFl/VeTgPOAoRW9r5BZdDnGK7baf64QwSyE8H3 z8UmXqAYfR+82M5Gwlyi9wVCMIIGNDCCBBygAwIBAgIBHjANBgkqhkiG9w0BAQUFADB9MQswCQYD VQQGEwJJTDEWMBQGA1UEChMNU3RhcnRDb20gTHRkLjErMCkGA1UECxMiU2VjdXJlIERpZ2l0YWwg Q2VydGlmaWNhdGUgU2lnbmluZzEpMCcGA1UEAxMgU3RhcnRDb20gQ2VydGlmaWNhdGlvbiBBdXRo b3JpdHkwHhcNMDcxMDI0MjEwMTU1WhcNMTcxMDI0MjEwMTU1WjCBjDELMAkGA1UEBhMCSUwxFjAU BgNVBAoTDVN0YXJ0Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRl IFNpZ25pbmcxODA2BgNVBAMTL1N0YXJ0Q29tIENsYXNzIDEgUHJpbWFyeSBJbnRlcm1lZGlhdGUg Q2xpZW50IENBMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxwmDzM4t2BqxKaQuE6uW vooyg4ymiEGWVUet1G8SD+rqvyNH4QrvnEIaFHxOhESip7vMz39ScLpNLbL1QpOlPW/tFIzNHS3q d2XRNYG5Sv9RcGE+T4qbLtsjjJbi6sL7Ls/f/X9ftTyhxvxWkf8KW37iKrueKsxw2HqolH7GM6FX 5UfNAwAu4ZifkpmZzU1slBhyWwaQPEPPZRsWoTb7q8hmgv6Nv3Hg9rmA1/VPBIOQ6SKRkHXG0Hhm q1dOFoAFI411+a/9nWm5rcVjGcIWZ2v/43Yksq60jExipA4l5uv9/+Hm33mbgmCszdj/Dthf13tg Av2O83hLJ0exTqfrlwIDAQABo4IBrTCCAakwDwYDVR0TAQH/BAUwAwEB/zAOBgNVHQ8BAf8EBAMC AQYwHQYDVR0OBBYEFFNy7ZKc4NrLAVx8fpY1TvLUuFGCMB8GA1UdIwQYMBaAFE4L7xqkQFulF2mH MMo0aEPQQa7yMGYGCCsGAQUFBwEBBFowWDAnBggrBgEFBQcwAYYbaHR0cDovL29jc3Auc3RhcnRz c2wuY29tL2NhMC0GCCsGAQUFBzAChiFodHRwOi8vd3d3LnN0YXJ0c3NsLmNvbS9zZnNjYS5jcnQw WwYDVR0fBFQwUjAnoCWgI4YhaHR0cDovL3d3dy5zdGFydHNzbC5jb20vc2ZzY2EuY3JsMCegJaAj hiFodHRwOi8vY3JsLnN0YXJ0c3NsLmNvbS9zZnNjYS5jcmwwgYAGA1UdIAR5MHcwdQYLKwYBBAGB tTcBAgEwZjAuBggrBgEFBQcCARYiaHR0cDovL3d3dy5zdGFydHNzbC5jb20vcG9saWN5LnBkZjA0 BggrBgEFBQcCARYoaHR0cDovL3d3dy5zdGFydHNzbC5jb20vaW50ZXJtZWRpYXRlLnBkZjANBgkq hkiG9w0BAQUFAAOCAgEACoMIfXirLAZcuGOMXq4cuSN3TaFx2H2GvD5VSy/6rV55BYHbWNaPeQn3 oBSU8KgQZn/Kck1JxbLpAxVCNtsxeW1R87ifhsYZ0qjdrA9anrW2MAWCtosmAOT4OxK9QPoSjCMx M3HbkZCDJgnlE8jMopH21BbyAYr7b5EfGRQJNtgWcvqSXwKHnTutR08+Kkn0KAkXCzeQNLeA5LlY UzFyM7kPAp8pIRMQ+seHunmyG642S2+y/qHEdMuGIwpfz3eDF1PdctL04qYK/zu+Qg1Bw0RwgigV Zs/0c5HP2/e9DBHh7eSwtzYlk4AUr6yxLlcwSjOfOmKEQ/Q8tzh0IFiNu9IPuTGAPBn4CPxD0+Ru 8T2wg8/s43R/PT3kd1OEqOJUl7q+h+r6fpvU0Fzxd2tC8Ga6fDEPme+1Nbi+03pVjuZQKbGwKJ66 gEn06WqaxVZC+J8hh/jR0k9mST1iAZPNYulcNJ8tKmVtjYsv0L1TSm2+NwON58tO+pIVzu3DWwSE XSf+qkDavQam+QtEOZxLBXI++aMUEapSn+k3Lxm48ZCYfAWLb/Xj7F5JQMbZvCexglAbYR0kIHqW 5DnsYSdMD/IplJMojx0NBrxJ3fN9dvX2Y6BIXRsF1du4qESm4/3CKuyUV7p9DW3mPlHTGLvYxnyK Qy7VFBkoLINszBrOUeIxggNvMIIDawIBATCBlDCBjDELMAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0 YXJ0Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNpZ25pbmcx ODA2BgNVBAMTL1N0YXJ0Q29tIENsYXNzIDEgUHJpbWFyeSBJbnRlcm1lZGlhdGUgQ2xpZW50IENB AgMN7zcwCQYFKw4DAhoFAKCCAa8wGAYJKoZIhvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0B CQUxDxcNMTUxMDI5MjIzNTI1WjAjBgkqhkiG9w0BCQQxFgQUtUR5+6JPcDIbyYjCKIMIH8uUmQYw gaUGCSsGAQQBgjcQBDGBlzCBlDCBjDELMAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0YXJ0Q29tIEx0 ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNpZ25pbmcxODA2BgNVBAMT L1N0YXJ0Q29tIENsYXNzIDEgUHJpbWFyeSBJbnRlcm1lZGlhdGUgQ2xpZW50IENBAgMN7zcwgacG CyqGSIb3DQEJEAILMYGXoIGUMIGMMQswCQYDVQQGEwJJTDEWMBQGA1UEChMNU3RhcnRDb20gTHRk LjErMCkGA1UECxMiU2VjdXJlIERpZ2l0YWwgQ2VydGlmaWNhdGUgU2lnbmluZzE4MDYGA1UEAxMv U3RhcnRDb20gQ2xhc3MgMSBQcmltYXJ5IEludGVybWVkaWF0ZSBDbGllbnQgQ0ECAw3vNzANBgkq hkiG9w0BAQEFAASCAQDAaz0mIa+iKE5WS4Vi1nkopZqIKrPxuu1PWZq/WrL9kJKlfV75zzvJarJD 66MpzIQngc9uEDzcAFHAd/2hhBo95/Pe+FNhHFbRLjgOm24Ix8rjsd/A2DuEzUfKe9orCS89Rec7 XXykcQKR0M2rbtll/YeTHWFtfaq7snaWQhwPeQ//ywRvTjpM5vtWbUIv4DsSPZeR626cGBtnkvve sEADxz8/wt4fpPKjYBvBFh352Gyhy59BwYJqUpT4cbQyK15DNe2mRhFuEF5uBmVjRgkF/gmL+hiS +OiOpImQQc1rUyXdfrQFCk2D8c7kYWsTG/+nt4EL9/Otgx7LSo/4YfcLAAAAAAAA --=-z+lA5ddzQUzAJBFdv6vn--