Re: [Xen-devel] [PATCH v3 2/8] hvmloader: Make the printfs more informative

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 21 Jun 2013, George Dunlap wrote:
> On 21/06/13 10:35, George Dunlap wrote:
> > On 20/06/13 18:12, Stefano Stabellini wrote:
> > > On Thu, 20 Jun 2013, George Dunlap wrote:
> > > > * Warn that you're relocating some BARs to 64-bit
> > > > 
> > > > * Warn that you're relocating guest pages, and how many
> > > > 
> > > > * Include upper 32-bits of the base register when printing the bar
> > > >    placement info
> > > > 
> > > > Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> > > > CC: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > > > CC: Ian Jackson <ian.jackson@xxxxxxxxxx>
> > > > CC: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> > > > CC: Hanweidong <hanweidong@xxxxxxxxxx>
> > > > CC: Keir Fraser <keir@xxxxxxx>
> > > > ---
> > > >   tools/firmware/hvmloader/pci.c |   13 ++++++++++---
> > > >   1 file changed, 10 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/tools/firmware/hvmloader/pci.c
> > > > b/tools/firmware/hvmloader/pci.c
> > > > index aa54bc1..d8592b0 100644
> > > > --- a/tools/firmware/hvmloader/pci.c
> > > > +++ b/tools/firmware/hvmloader/pci.c
> > > > @@ -213,10 +213,17 @@ void pci_setup(void)
> > > >               ((pci_mem_start << 1) != 0) )
> > > >           pci_mem_start <<= 1;
> > > >   -    if ( (pci_mem_start << 1) != 0 )
> > > > +    if ( (pci_mem_start << 1) != 0 ) {
> > > > +        printf("Low MMIO hole not large enough for all devices,"
> > > > +               " relocating some BARs to 64-bit\n");
> > > >           bar64_relocate = 1;
> > > > +    }
> > > >         /* Relocate RAM that overlaps PCI space (in 64k-page chunks). */
> > > > +    if ( (pci_mem_start >> PAGE_SHIFT) < hvm_info->low_mem_pgend )
> > > > +        printf("Relocating 0x%lx pages to highmem for lowmem MMIO
> > > > hole\n",
> > > > +               hvm_info->low_mem_pgend - (pci_mem_start >>
> > > > PAGE_SHIFT));
> > > Shouldn't this be:
> > > 
> > > min_t(unsigned int,
> > >        hvm_info->low_mem_pgend - (pci_mem_start >> PAGE_SHIFT),
> > >        (1u << 16) - 1);
> > > 
> > > to match exactly what we do in the relocation code?
> > 
> > No; the relocation is done in a loop which will run until the condition in
> > the if above is satisfied.
> > 
> > We could, I suppose, do the printf on each iteration of the loop; if I'm
> > doing the math right*, the maximum iterations around the loop should be 8,
> > and a typical number would be just 1 or 2.
> > 
> > * Maximum MMIO size: 2GiB == 1<<31.  In 4-k pages, that's 1<<(31-12) ==
> > 1<<19.  This will do a batch of 1<<16 pages at a time, leaving 1<<3
> > iterations maximum, or 8.  (1<<16 pages is 1<<(16+12) or 1<<28 bytes, or
> > 1<<8 == 256 megabytes moved at a time.)
> > 
> > > 
> > > Regarding the message, what about:
> > > 
> > > printf("Relocating 0x%lx pages from 0x%lx to 0x%lx%lx to make room for a
> > > larger MMIO hole\n",
> > >         min_t(unsigned int,
> > >               hvm_info->low_mem_pgend - (pci_mem_start >> PAGE_SHIFT),
> > >               (1u << 16) - 1),
> > >          hvm_info->low_mem_pgend,
> > >          hvm_info->high_mem_pgend);
> > 
> > Lemme see how it looks...
> 
> If you have a 2GiB MMIO hole, it looks like this:
> 
> (XEN) HVM42: Relocating 0xffff pages from 0e0001000 to 20f800000 for lowmem
> MMIO hole
> (XEN) HVM42: Relocating 0xffff pages from 0d0002000 to 21f7ff000 for lowmem
> MMIO hole
> (XEN) HVM42: Relocating 0xffff pages from 0c0003000 to 22f7fe000 for lowmem
> MMIO hole
> (XEN) HVM42: Relocating 0xffff pages from 0b0004000 to 23f7fd000 for lowmem
> MMIO hole
> (XEN) HVM42: Relocating 0xffff pages from 0a0005000 to 24f7fc000 for lowmem
> MMIO hole
> (XEN) HVM42: Relocating 0xffff pages from 090006000 to 25f7fb000 for lowmem
> MMIO hole
> (XEN) HVM42: Relocating 0xffff pages from 080007000 to 26f7fa000 for lowmem
> MMIO hole
> (XEN) HVM42: Relocating 0x7 pages from 080000000 to 27f7f9000 for lowmem MMIO
> hole
> 
> 
> Kind of ugly; I think I liked it better with just one printf.

I agree

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