| Message ID | 20211118192020.61245-1-philmd@redhat.com |
|---|---|
| Headers | show |
| Series | hw/display: Do not allow multiple (identical) VGA devices | expand |
On 18/11/2021 19:20, Philippe Mathieu-Daudé wrote: > Commit 7852a77f598 fixed creating multiple TYPE_ISA_VGA devices, > generalize the fix to all VGA devices. > > See https://gitlab.com/qemu-project/qemu/-/issues/44 > > Philippe Mathieu-Daudé (2): > hw/display: Add Error* handle to vga_common_init() > hw/display: Do not allow multiple identical VGA devices > > hw/display/vga_int.h | 2 +- > hw/display/ati.c | 4 +++- > hw/display/cirrus_vga.c | 4 +++- > hw/display/cirrus_vga_isa.c | 4 +++- > hw/display/qxl.c | 4 +++- > hw/display/vga-isa-mm.c | 3 ++- > hw/display/vga-isa.c | 11 ++--------- > hw/display/vga-pci.c | 8 ++++++-- > hw/display/vga.c | 17 ++++++++++++++++- > hw/display/virtio-vga.c | 4 +++- > hw/display/vmware_vga.c | 2 +- > 11 files changed, 43 insertions(+), 20 deletions(-) Hi Phil, I don't think this is correct for non-ISA devices: for example years ago I had a PC running Windows 98SE with 2 identical PCI graphics cards configured in dual-head mode. IIRC the BIOS would bring up the first graphics card and configure it to use the legacy ISA VGA ioports for compatibility, and then once the main OS drivers loaded both cards were switched to PCI mode and configured using the BARs as normal. ATB, Mark.
On 11/19/21 09:21, Mark Cave-Ayland wrote: > On 18/11/2021 19:20, Philippe Mathieu-Daudé wrote: > >> Commit 7852a77f598 fixed creating multiple TYPE_ISA_VGA devices, >> generalize the fix to all VGA devices. >> >> See https://gitlab.com/qemu-project/qemu/-/issues/44 >> >> Philippe Mathieu-Daudé (2): >> hw/display: Add Error* handle to vga_common_init() >> hw/display: Do not allow multiple identical VGA devices >> >> hw/display/vga_int.h | 2 +- >> hw/display/ati.c | 4 +++- >> hw/display/cirrus_vga.c | 4 +++- >> hw/display/cirrus_vga_isa.c | 4 +++- >> hw/display/qxl.c | 4 +++- >> hw/display/vga-isa-mm.c | 3 ++- >> hw/display/vga-isa.c | 11 ++--------- >> hw/display/vga-pci.c | 8 ++++++-- >> hw/display/vga.c | 17 ++++++++++++++++- >> hw/display/virtio-vga.c | 4 +++- >> hw/display/vmware_vga.c | 2 +- >> 11 files changed, 43 insertions(+), 20 deletions(-) > > Hi Phil, > > I don't think this is correct for non-ISA devices: for example years ago > I had a PC running Windows 98SE with 2 identical PCI graphics cards > configured in dual-head mode. > > IIRC the BIOS would bring up the first graphics card and configure it to > use the legacy ISA VGA ioports for compatibility, and then once the main > OS drivers loaded both cards were switched to PCI mode and configured > using the BARs as normal. The problem here is QEMU technical debt, not the hardware. When vga_common_init() calls memory_region_init_ram_nomigrate() with obj=NULL, "vga.vram" is registered as a QOM singleton. Updating it would 1/ require non-QOM devices to be QOM'ified and 2/ break migration unless using HPFM which I don't master.
On 19/11/2021 10.49, Philippe Mathieu-Daudé wrote: > On 11/19/21 09:21, Mark Cave-Ayland wrote: >> On 18/11/2021 19:20, Philippe Mathieu-Daudé wrote: >> >>> Commit 7852a77f598 fixed creating multiple TYPE_ISA_VGA devices, >>> generalize the fix to all VGA devices. >>> >>> See https://gitlab.com/qemu-project/qemu/-/issues/44 >>> >>> Philippe Mathieu-Daudé (2): >>> hw/display: Add Error* handle to vga_common_init() >>> hw/display: Do not allow multiple identical VGA devices >>> >>> hw/display/vga_int.h | 2 +- >>> hw/display/ati.c | 4 +++- >>> hw/display/cirrus_vga.c | 4 +++- >>> hw/display/cirrus_vga_isa.c | 4 +++- >>> hw/display/qxl.c | 4 +++- >>> hw/display/vga-isa-mm.c | 3 ++- >>> hw/display/vga-isa.c | 11 ++--------- >>> hw/display/vga-pci.c | 8 ++++++-- >>> hw/display/vga.c | 17 ++++++++++++++++- >>> hw/display/virtio-vga.c | 4 +++- >>> hw/display/vmware_vga.c | 2 +- >>> 11 files changed, 43 insertions(+), 20 deletions(-) >> >> Hi Phil, >> >> I don't think this is correct for non-ISA devices: for example years ago >> I had a PC running Windows 98SE with 2 identical PCI graphics cards >> configured in dual-head mode. >> >> IIRC the BIOS would bring up the first graphics card and configure it to >> use the legacy ISA VGA ioports for compatibility, and then once the main >> OS drivers loaded both cards were switched to PCI mode and configured >> using the BARs as normal. > > The problem here is QEMU technical debt, not the hardware. > > When vga_common_init() calls memory_region_init_ram_nomigrate() > with obj=NULL, "vga.vram" is registered as a QOM singleton. > > Updating it would > 1/ require non-QOM devices to be QOM'ified So sounds like that's the right way to go here. > and 2/ break migration unless using HPFM which I don't master. What's HPFM? Thomas
On 11/19/21 10:58, Thomas Huth wrote: > On 19/11/2021 10.49, Philippe Mathieu-Daudé wrote: >> On 11/19/21 09:21, Mark Cave-Ayland wrote: >>> On 18/11/2021 19:20, Philippe Mathieu-Daudé wrote: >>> >>>> Commit 7852a77f598 fixed creating multiple TYPE_ISA_VGA devices, >>>> generalize the fix to all VGA devices. >>>> >>>> See https://gitlab.com/qemu-project/qemu/-/issues/44 >>>> >>>> Philippe Mathieu-Daudé (2): >>>> hw/display: Add Error* handle to vga_common_init() >>>> hw/display: Do not allow multiple identical VGA devices >>>> >>>> hw/display/vga_int.h | 2 +- >>>> hw/display/ati.c | 4 +++- >>>> hw/display/cirrus_vga.c | 4 +++- >>>> hw/display/cirrus_vga_isa.c | 4 +++- >>>> hw/display/qxl.c | 4 +++- >>>> hw/display/vga-isa-mm.c | 3 ++- >>>> hw/display/vga-isa.c | 11 ++--------- >>>> hw/display/vga-pci.c | 8 ++++++-- >>>> hw/display/vga.c | 17 ++++++++++++++++- >>>> hw/display/virtio-vga.c | 4 +++- >>>> hw/display/vmware_vga.c | 2 +- >>>> 11 files changed, 43 insertions(+), 20 deletions(-) >>> >>> Hi Phil, >>> >>> I don't think this is correct for non-ISA devices: for example years ago >>> I had a PC running Windows 98SE with 2 identical PCI graphics cards >>> configured in dual-head mode. >>> >>> IIRC the BIOS would bring up the first graphics card and configure it to >>> use the legacy ISA VGA ioports for compatibility, and then once the main >>> OS drivers loaded both cards were switched to PCI mode and configured >>> using the BARs as normal. >> >> The problem here is QEMU technical debt, not the hardware. >> >> When vga_common_init() calls memory_region_init_ram_nomigrate() >> with obj=NULL, "vga.vram" is registered as a QOM singleton. >> >> Updating it would >> 1/ require non-QOM devices to be QOM'ified > > So sounds like that's the right way to go here. > >> and 2/ break migration unless using HPFM which I don't master. > > What's HPFM? Hocus Pocus Freakin' Magic
On 19/11/2021 11.17, Philippe Mathieu-Daudé wrote: > On 11/19/21 10:58, Thomas Huth wrote: >> On 19/11/2021 10.49, Philippe Mathieu-Daudé wrote: >>> On 11/19/21 09:21, Mark Cave-Ayland wrote: >>>> On 18/11/2021 19:20, Philippe Mathieu-Daudé wrote: >>>> >>>>> Commit 7852a77f598 fixed creating multiple TYPE_ISA_VGA devices, >>>>> generalize the fix to all VGA devices. >>>>> >>>>> See https://gitlab.com/qemu-project/qemu/-/issues/44 >>>>> >>>>> Philippe Mathieu-Daudé (2): >>>>> hw/display: Add Error* handle to vga_common_init() >>>>> hw/display: Do not allow multiple identical VGA devices >>>>> >>>>> hw/display/vga_int.h | 2 +- >>>>> hw/display/ati.c | 4 +++- >>>>> hw/display/cirrus_vga.c | 4 +++- >>>>> hw/display/cirrus_vga_isa.c | 4 +++- >>>>> hw/display/qxl.c | 4 +++- >>>>> hw/display/vga-isa-mm.c | 3 ++- >>>>> hw/display/vga-isa.c | 11 ++--------- >>>>> hw/display/vga-pci.c | 8 ++++++-- >>>>> hw/display/vga.c | 17 ++++++++++++++++- >>>>> hw/display/virtio-vga.c | 4 +++- >>>>> hw/display/vmware_vga.c | 2 +- >>>>> 11 files changed, 43 insertions(+), 20 deletions(-) >>>> >>>> Hi Phil, >>>> >>>> I don't think this is correct for non-ISA devices: for example years ago >>>> I had a PC running Windows 98SE with 2 identical PCI graphics cards >>>> configured in dual-head mode. >>>> >>>> IIRC the BIOS would bring up the first graphics card and configure it to >>>> use the legacy ISA VGA ioports for compatibility, and then once the main >>>> OS drivers loaded both cards were switched to PCI mode and configured >>>> using the BARs as normal. >>> >>> The problem here is QEMU technical debt, not the hardware. >>> >>> When vga_common_init() calls memory_region_init_ram_nomigrate() >>> with obj=NULL, "vga.vram" is registered as a QOM singleton. >>> >>> Updating it would >>> 1/ require non-QOM devices to be QOM'ified >> >> So sounds like that's the right way to go here. >> >>> and 2/ break migration unless using HPFM which I don't master. >> >> What's HPFM? > > Hocus Pocus Freakin' Magic LOL, ok, thanks, TIL. Anyway, IMHO I'd rather fix this issue by properly QOM'ifying the vga-isa-mm.c code and breaking migration here (who's migrating such old ISA devices anyway?) instead of introducing more kludges that might cause other trouble (see also https://gitlab.com/qemu-project/qemu/-/issues/733 ). Thomas