From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chen, Tiejun" Subject: Re: [v6][PATCH 2/2] xen:vtd: missing RMRR mapping while share EPT Date: Fri, 19 Sep 2014 15:40:28 +0800 Message-ID: <541BDDEC.2070007@intel.com> References: <1406684186-12788-1-git-send-email-tiejun.chen@intel.com> <1406684186-12788-2-git-send-email-tiejun.chen@intel.com> <541ABD800200007800036113@mail.emea.novell.com> <541B84C1.4000403@intel.com> <541BE899020000780003668C@mail.emea.novell.com> <541BD249.3030204@intel.com> <541BF2EA02000078000366E6@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <541BF2EA02000078000366E6@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: yang.z.zhang@intel.com, kevin.tian@intel.com, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 2014/9/19 15:10, Jan Beulich wrote: >>>> On 19.09.14 at 08:50, wrote: >> On 2014/9/19 14:26, Jan Beulich wrote: >>>>>> On 19.09.14 at 03:20, wrote: >>>> (XEN) [VT-D]dmar.c:807: found ACPI_DMAR_RMRR: >>>> (XEN) [VT-D]dmar.c:383: endpoint: 0000:00:14.0 >>>> (XEN) [VT-D]dmar.c:676: RMRR region: base_addr ab805000 end_address >>>> ab818fff >>>> (XEN) [VT-D]dmar.c:807: found ACPI_DMAR_RMRR: >>>> (XEN) [VT-D]dmar.c:383: endpoint: 0000:00:02.0 >>>> (XEN) [VT-D]dmar.c:676: RMRR region: base_addr ad000000 end_address >>>> af7fffff >>> >>> So how does passing through either of these work for a guest with >>> 4Gb or more of memory assigned with just the original 2 patches >>> (and with shared page tables)? There ought to be a collision detected >>> when trying to do the identity mapping. >> >> Do you mean this point, mfn_valid(mfn)? If yes, I remember we made >> agreement previously about how to cover three cases including this scenario: >> >> " >> #1: !mfn_valid(mfn) >> >> We can create those mapping safely. >> >> #2: mfn_x(mfn) == gfn && p2mt == p2m_mmio_direct && a == p2m_access_rw >> >> We already have these matched mappings. >> >> #3: Others >> >> Return with that waring message: "Cannot identity map d%d:%lx, already >> mapped to %lx but mismatch.\n" >> " >> And this is just as we did in patch #1: >> >> + >> + if ( !mfn_valid(mfn) ) >> + ret = p2m_set_entry(p2m, gfn, _mfn(gfn), PAGE_ORDER_4K, >> p2m_mmio_direct, >> + p2m_access_rw); >> + else if ( mfn_x(mfn) == gfn && >> + p2mt == p2m_mmio_direct && >> + a == p2m_access_rw ) >> + ret = 0; >> + else >> + printk(XENLOG_G_WARNING >> + "Cannot identity map d%d:%lx, already mapped to %lx.\n", >> + d->domain_id, gfn, mfn_x(mfn)); > > Right, but the important point is that when the warning gets printed > -EBUSY gets returned, i.e. in the end the device assignment is to fail. > Are you seeing the warning when creating a large enough guest? If My platform just own 4G memory, so after I try to set 'memory=15360' in domu.cfg, I can't boot such a VM: # xl cr domu.cfg Parsing config from domu.cfg libxl: error: libxl.c:4202:libxl_set_memory_target: new target 0 for dom0 is below the minimum threshhold ... failed to free memory for the domain > not - can you explain why you don't see it (as I can't)? Do you know exactly how to test this case as you expect here? Then I can take a further look to step on your question. Or I guess you are hinting something wrong should be happened but I never realize that previously. Thanks Tiejun > > Jan > > >