_IO_IS_ISA question

linas at austin.ibm.com linas at austin.ibm.com
Thu Mar 25 05:22:00 EST 2004

Hi Jake,

Reviewed the patch...  that patch looked reasonable from what I
could tell; I have one request: could you cut&paste some portion
of this email into the comments for that code? e.g. the second
paragaph could go into the include/asm/eeh.h file right before
the eeh_in* macros ....


On Wed, Mar 17, 2004 at 02:57:18PM +0000, Jake Moilanen wrote:
> After further investigation, I realize why this was done.  What will
> happen is that a ISA device like the 8250 serial will try doing
> inb/outb's to the ISA space to detect the device.  This will cause a
> page fault and the kernel will attempt to create a PTE for this page.
> On a hypervisor system, if the ISA device is not assigned to that
> partition, the address will cause the H_ENTER to fail with a H_PARM.
> This will cause the kernel to panic.  So this code was blocking ISA IO
> range accesses when there wasn't a ISA bus.
> I wrote a patch to create a valid mask of pages that a PCI device can
> access inside the ISA IO range.  It will punch holes into this mask
> while probing the PCI devices.  FW must either give us full access to a
> page, or not.  So we do not have to worry about a valid PCI device IO
> range and a invalid ISA device IO range overlapping within the same
> page.
> Thanks,
> Jake

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