linux-kernel - Re: [Qemu-devel] Re: ACPI error when mapping a 2GB BAR w/ 4GB of RAM

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Date:	Fri, 17 Sep 2010 15:45:38 -0600
From:	Cam Macdonell <cam@...ualberta.ca>
To:	Chris Wright <chrisw@...hat.com>
Cc:	"qemu-devel@...gnu.org Developers" <qemu-devel@...gnu.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [Qemu-devel] Re: ACPI error when mapping a 2GB BAR w/ 4GB of RAM

On Fri, Sep 17, 2010 at 3:15 PM, Chris Wright <chrisw@...hat.com> wrote:
> * Cam Macdonell (cam@...ualberta.ca) wrote:
>> On Fri, Sep 17, 2010 at 2:52 PM, Cam Macdonell <cam@...ualberta.ca> wrote:
>> > On Fri, Sep 17, 2010 at 2:04 PM, Chris Wright <chrisw@...hat.com> wrote:
>> >> * Cam Macdonell (cam@...ualberta.ca) wrote:
>> >>> After fixing the resource_size_t return value with
>> >>> pci_resource_alignment, I see one other strange behaviour only when
>> >>> using 4GB of RAM and a 2GB BAR.  I haven't found any other combination
>> >>> of RAM/BAR size that triggers this bug.  I am using 2.6.36-rc3.
>> >>>
>> >>> ACPI Error: The DSDT has been corrupted or replaced - old, new headers
>> >>> below (20100702/tbutils-372)
>> >>> ACPI: DSDT (null) 01F15 (v01   BXPC   BXDSDT 00000001 INTL 20090123)
>> >>> ACPI:      (null) 00000 (v00                 00000000      00000000)
>> >>> ACPI Error: Please send DMI info to linux-acpi@...r.kernel.org
>> >>> If system does not work as expected, please boot with acpi=copy_dsdt
>> >>> (20100702/tbutils-378)
>> >>> ACPI: PCI Interrupt Link [LNKC] disabled and referenced, BIOS bug
>> >>> ACPI Exception: AE_AML_INVALID_RESOURCE_TYPE, Evaluating _CRS
>> >>> (20100702/pci_link-283)
>> >>> ACPI: Unable to set IRQ for PCI Interrupt Link [LNKC]. Try pci=noacpi
>> >>> or acpi=off
>> >>> virtio-pci 0000:00:03.0: PCI INT A: no GSI - using ISA IRQ 11
>> >>> Non-volatile memory driver v1.3
>> >>> Linux agpgart interface v0.103
>> >>> Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
>> >>
>> >> IIRC,  the pci hole is only 1.5G in the BIOS, can you verify that
>> >> seabios is doing the right thing?
>> >
>> > I'm not sure what the right thing for seabios to do is.  Here is the
>> > seabios output related to the device.
>> >
>> > PCI: bus=0 devfn=0x20: vendor_id=0x1af4 device_id=0x1110
>> > region 0: 0xf2040000
>> > init smm
>> > init boot device ordering
>> >
>> > <snip>
>> >
>> > Attempting to init PCI bdf 00:04.0 (vd 1af4:1110)
>> > Attempting to map option rom on dev 00:04.0
>> > Option rom sizing returned 0 0
>> > Checking rom 0x000c9800 (sig aa55 size 17)
>> > Checking rom 0x000cc000 (sig aa55 size 2)
>> > Checking rom 0x000c9000 (sig aa55 size 4)
>> > Checking rom 0x000c9800 (sig aa55 size 17)
>> > Checking rom 0x000cc000 (sig aa55 size 2)
>> > Mapping hd drive 0x000fdb50 to 0
>> > Running option rom at c980:0003
>> > Running option rom at cc00:0003
>> > pmm_malloc zone=0x000f515c handle=ffffffff size=36 align=10
>> > ret=0x000fdaf0 (detail=0x7ffefca0)
>> > ebda moved from 9fc00 to 9f400
>> > pmm_malloc zone=0x000f5154 handle=ffffffff size=2048 align=10
>> > ret=0x0009f800 (detail=0x7ffefb40)
>> > finalize PMM
>> > malloc finalize
>> >
>> > when using a BAR of 2GB or less, there is an additional write to the
>> > PCI space of the device, which may be from the bios
>> >
>> > pci_write_config: (val) 0xffffffff -> 0x18 (addr)
>> > pci_read_config: (val) 0x80000004 <- 0x18 (addr)
>> > pci_write_config: (val) 0x4 -> 0x18 (addr)
>> > pci_write_config: (val) 0x3 -> 0x4 (addr)
>> > pci_read_config: (val) 0x0 <- 0x1c (addr)
>> > pci_write_config: (val) 0xffffffff -> 0x1c (addr)
>> > IVSHMEM: guest pci addr = ffffffff00000000, guest h/w addr =
>> > 4312137728, size = 80000000
>> >
>> > so is it succeeding with smaller sizes (> 2GB) because it fits in the
>> > bios' pci hole?
>>
>> sorry that should be "< 2GB".
>
> It seems most likely...< 2GB also means <= 1GB (which would fit in
> the hole).  Although, I have to admit, I'm not sure how seabios handles
> the hole nowadays.
>
> What about 2GB with 32bit BAR?

The bios seems to ignore it and the guest can't map it as it cannot
find an alignment for it.  Seems strange since with 1GB of RAM and 2GB
BAR, everything should map below 4GB.

>
> thanks,
> -chris
>
>
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