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

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

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...

 -George

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