From mboxrd@z Thu Jan 1 00:00:00 1970 From: Weidong Han Subject: Re: [PATCH] VT-d: improve RMRR validity checking Date: Tue, 26 Jan 2010 13:51:13 +0800 Message-ID: <4B5E82D1.8060206@intel.com> References: <4B5DA659.1030506@intel.com> <4B5E4276.90308@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------010607070301080701070101" Return-path: In-Reply-To: <4B5E4276.90308@jp.fujitsu.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Noboru Iwamatsu Cc: "linux@eikelenboom.it" , "Cihula, Joseph" , "xen-devel@lists.xensource.com" , "Kay, Allen M" , "keir.fraser@eu.citrix.com" List-Id: xen-devel@lists.xenproject.org This is a multi-part message in MIME format. --------------010607070301080701070101 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit I implemented a patch for it. Noboru, pls have a try on your machine. If you use default iommu=1, VT-d will be disabled with warning messages. If you use iommu=workaround_bios_bug, it should enable VT-d and works for you. If you use iommu=force, it panics. patch title: VT-d: add "iommu=workaround_bios_bug" option patch description: Add this option to workaround BIOS bugs. Currently it ignores DRHD if "all" devices under its scope are not pci discoverable. This workarounds a BIOS bug in some platforms to make VT-d work. But note that this option doesn't guarantee security, because it might ignore DRHD. So there are 3 options which handle BIOS bugs differently: iommu=1 (default): If detect non-existent device under a DRHD's scope, or find incorrect RMRR setting (base_address > end_address), disable VT-d completely in Xen with warning messages. This guarantees security when VT-d enabled, or just disable VT-d to let Xen work without VT-d. iommu=force: it enforces to enable VT-d in Xen. If VT-d cannot be enabled, it will crashes Xen. This is mainly for users who must need VT-d. iommu=workaround_bogus_bios: it workarounds some BIOS bugs to make VT-d still work. This might be insecure because there might be a device not protected by any DRHD if the device is re-enabled by malicious s/w. This is for users who want to use VT-d regardless of security. Signed-off-by: Weidong Han Regards, Weidong Noboru Iwamatsu wrote: > Weidong, Keir, > > I agree your suggestions. > > Noboru. > > >> Keir Fraser wrote: >> >>> On 25/01/2010 10:45, "Sander Eikelenboom" wrote: >>> >>> >>>> a) Could be discussed if panic should be default instead of disabling >>>> iommu or >>>> not, although there seem to be a lot of broken bioses, so that would >>>> lead to a >>>> lot of machines not booting. >>>> >>> Absolutely not acceptable. Warn and completely disable IOMMU is the >>> correct >>> default causing least pain to the most end users. >>> >>> -- Keir >>> >>> >> Agree. It should not crash Xen by default due to BIOS issues. >> warn-and-disable is better. It won't impact common Xen users, and if a >> user really wants to use VT-d, he can try iommu=workaround_bogus_bios, >> or directly report to OEM vendor to get it fixed in BIOS. As VT-d is >> used more and more widely, I think the BIOS issues will be found and >> fixed more quickly than before, thus the situation should be better. >> >> Regards, >> Weidong >> >> >> >> > > > --------------010607070301080701070101 Content-Type: text/plain; name="workaround-bios.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="workaround-bios.patch" diff -r 5dabbf2826c5 xen/drivers/passthrough/iommu.c --- a/xen/drivers/passthrough/iommu.c Mon Jan 25 09:58:53 2010 +0800 +++ b/xen/drivers/passthrough/iommu.c Tue Jan 26 21:17:46 2010 +0800 @@ -30,6 +30,8 @@ static int iommu_populate_page_table(str * pv Enable IOMMU for PV domains * no-pv Disable IOMMU for PV domains (default) * force|required Don't boot unless IOMMU is enabled + * workaround_bios_bug Workaround some bios issue to still enable + VT-d, don't guarantee security * passthrough Enable VT-d DMA passthrough (no DMA * translation for Dom0) * no-snoop Disable VT-d Snoop Control @@ -40,6 +42,7 @@ int iommu_enabled = 1; int iommu_enabled = 1; int iommu_pv_enabled; int force_iommu; +int iommu_workaround_bios_bug; int iommu_passthrough; int iommu_snoop = 1; int iommu_qinval = 1; @@ -65,6 +68,8 @@ static void __init parse_iommu_param(cha iommu_pv_enabled = 0; else if ( !strcmp(s, "force") || !strcmp(s, "required") ) force_iommu = 1; + else if ( !strcmp(s, "workaround_bios_bug") ) + iommu_workaround_bios_bug = 1; else if ( !strcmp(s, "passthrough") ) iommu_passthrough = 1; else if ( !strcmp(s, "no-snoop") ) diff -r 5dabbf2826c5 xen/drivers/passthrough/vtd/dmar.c --- a/xen/drivers/passthrough/vtd/dmar.c Mon Jan 25 09:58:53 2010 +0800 +++ b/xen/drivers/passthrough/vtd/dmar.c Tue Jan 26 21:16:49 2010 +0800 @@ -421,17 +421,21 @@ acpi_parse_one_drhd(struct acpi_dmar_ent if ( invalid_cnt ) { xfree(dmaru); - if ( invalid_cnt == dmaru->scope.devices_cnt ) + + if ( iommu_workaround_bios_bug && + invalid_cnt == dmaru->scope.devices_cnt ) { dprintk(XENLOG_WARNING VTDPREFIX, - " Ignore the DRHD due to all devices under " - "its scope are not PCI discoverable!\n"); + " Workaround BIOS bug: ignore the DRHD due to all " + "devices under its scope are not PCI discoverable!\n"); } else { dprintk(XENLOG_WARNING VTDPREFIX, - " The DRHD is invalid due to some devices under " - "its scope are not PCI discoverable!\n"); + " The DRHD is invalid due to there are devices under " + "its scope are not PCI discoverable! Pls try option " + "iommu=force or iommu=workaround_bios_bug if you " + "really want VT-d\n"); ret = -EINVAL; } } diff -r 5dabbf2826c5 xen/include/xen/iommu.h --- a/xen/include/xen/iommu.h Mon Jan 25 09:58:53 2010 +0800 +++ b/xen/include/xen/iommu.h Tue Jan 26 21:17:08 2010 +0800 @@ -29,6 +29,7 @@ extern int iommu_enabled; extern int iommu_enabled; extern int iommu_pv_enabled; extern int force_iommu; +extern int iommu_workaround_bios_bug; extern int iommu_passthrough; extern int iommu_snoop; extern int iommu_qinval; --------------010607070301080701070101 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel --------------010607070301080701070101--