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BVgOyYXeG353j1tVisCXvbcKN4.FvXKnWLO93apxLqjJr7lC83rF7LGwv0dLctXl.YeOrjufru2Z aUc3fyahR3mMfn_TloHA.YySi34EA14R3oIYtvPY.52VT4HsIoBT4P4jRH16Kwt0LCr2DKQnJaMs n68HxaxiTBPCKJB9reZvcE3P02hGbfztlRLTbeajagXH8UF4ESU0vNYOezLWPQGmwCyGOX.EfEMy NN.lRZRyHtAZQCPak5BEEp4Gq5gg1DMfDtJLZ.Rl_HnnxeREkasSWQDg4rttWrlBvKS3o8FjWqkq Lpb89l8bE5IVDYYTyz3ULMrGmaY6RsHAOa3rQepAJ7fwjMXZffCNBARD3d3hSxnckohu0n1VvOvI 5aDUHnQ9nVVmmqHatNAvmhbdnz3YhUq7aRukyWtW7aLyYVoJAZ_xQQ1b.qmLVoUjXam1l2ee4hJd dHpnL3MWXDAL4KFJmJClOeSl_JPTB0xb3OGqkcRrA.yOg8swos.UbYOr91vbgYQ8ZmzVLpQWuw.Z Ajh5WwouIBj2lwD8oXKCgRZJkC.HL_B_GjRzO_W2fuA-- X-Sonic-MF: X-Sonic-ID: b8452a40-21fd-4249-b0e5-ba6658385c4b Message-ID: <1522d7a3-eb9d-40df-9a34-7b1cfeb3680e@aol.com> Date: Fri, 14 Aug 2026 12:18:26 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] tools/hvmloader: implement Intel IGD extended VBT support From: Chuck Zmudzinski To: Jan Beulich Cc: qemu-devel@nongnu.org, Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Teddy Astie , Tomita Moeko , xen-devel , Anthony PERARD References: <20260802050824.10554-1-brchuckz.ref@aol.com> <20260802050824.10554-1-brchuckz@aol.com> <2110d4b7-ae37-47aa-99be-ab59e16f6167@suse.com> <67579eba-e222-41dd-84bf-8440d2eaf2a9@netscape.net> <02a7dc18-4184-4e86-84cb-121769187f71@suse.com> <1858e8e6-73fa-4017-93e2-c733fbf0ec8d@aol.com> Content-Language: en-US In-Reply-To: <1858e8e6-73fa-4017-93e2-c733fbf0ec8d@aol.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Mailer: WebService/1.1.26254 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.aol X-purgate-ID: tlsNG-33051d/1786724313-7428D4E9-007C5BBF/0/0 X-purgate-type: clean X-purgate-size: 2209 On 8/14/2026 11:23 AM, Chuck Zmudzinski wrote: > On 8/14/2026 9:46 AM, Jan Beulich wrote: >> On 14.08.2026 15:18, Chuck Zmudzinski wrote: >>> On 8/14/2026 3:35 AM, Jan Beulich wrote: >>>> On 14.08.2026 02:45, Chuck Zmudzinski wrote: >>>>> On 8/13/2026 6:35 AM, Jan Beulich wrote: >>>>>> On 02.08.2026 07:08, Chuck Zmudzinski wrote: >>>>>>> -- snip -- >>>> >>>> I don't follow this: Anything the guest can access should also be accessible >>>> by its DM. >>> >>> I think the host OpRegion is not currently accessible by the DM. >> >> Can you explain to me how the region becomes accessible to the guest? >> That would then (hopefully) help me understand why the DM would not have >> access. Fundamentally any MMIO and any I/O ports that are assigned to a >> guest are also assigned to its DM. > > Currently, in the device model (Qemu) we have: > > ret = xc_domain_memory_mapping(xen_xc, xen_domid, > (unsigned long)(igd_guest_opregion >> XC_PAGE_SHIFT), > (unsigned long)(igd_host_opregion >> XC_PAGE_SHIFT), > XEN_PCI_INTEL_OPREGION_PAGES, > DPCI_ADD_MAPPING); > > That statement is in the igd_write_opregion(...) function in the > hw/xen/xen_pt_graphics.c file of the upstream Qemu source. I forgot to mention: In our current implementation, this statement is executed in the DM when hvmloader executes this statement, currently in hvmloader/pci: pci_writel(vga_devfn, PCI_INTEL_OPREGION, igd_opregion_pgbase << PAGE_SHIFT); > > If I understand our current implementation correctly, this statement > is what gives the guest access to the host OpRegion (3 pages as defined > by XEN_PCI_INTEL_OPREGION_PAGES, and in agreement with IGD_OPREGION_PAGES > in hvmloader code). I don't think this statement makes the host OpRegion > accessible to the device model, though, so I think, if I understand your > comment in an earlier about my patch resulting in what you called a "layering > violation" correctly, that our current implementation is also guilty of this > same kind of "layering violation." > > So, how do you suggest we fix that? > ...