Re: [PATCH 2/2] x86/PCI: limit the size of the 64bit window to 256GB v3

[Christian KÃnig]

Am 11.01.2018 um 15:21 schrieb Bjorn Helgaas:
> On Thu, Jan 11, 2018 at 02:23:30PM +0100, Christian KÃnig wrote:
> > Avoid problems with BIOS implementations which don't report all used
> > resources to the OS by only allocating a 256GB window directly below the
> > hardware limit.
> >
> > For the full hardware documentation see:
> > https://support.amd.com/TechDocs/49125_15h_Models_30h-3Fh_BKDG.pdf
> If you can supply a section number, I'll add it here.  That spec is 700
> pages, so a hint would be useful.

Sorry, had to search for that as well. That is noted in section "2.4.6 
System Address Map".

Do you want to add that or should I resend the patch?

Regards,
Christian.

> > Fixes a silent reboot loop reported by Aaro Koskinen <aaro.koskinen@xxxxxx> on
> > an AMD-based MSI MS-7699/760GA-P43(FX) system.
> >
> > v2: cleanup code a bit more, update comment and explain the hw limit
> > v3: improve commit message
> >
> > Link: https://lkml.kernel.org/r/20180105220412.fzpwqe4zljdawr36@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Reported-by: Aaro Koskinen <aaro.koskinen@xxxxxx>
> > Signed-off-by: Christian KÃnig <christian.koenig@xxxxxxx>
> > ---
> >   arch/x86/pci/fixup.c | 19 +++++++++----------
> >   1 file changed, 9 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/x86/pci/fixup.c b/arch/x86/pci/fixup.c
> > index a91280da2ea1..9c1c98d7e3a7 100644
> > --- a/arch/x86/pci/fixup.c
> > +++ b/arch/x86/pci/fixup.c
> > @@ -662,10 +662,11 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x2033, quirk_no_aersid);
> >    */
> >   static void pci_amd_enable_64bit_bar(struct pci_dev *dev)
> >   {
> > -	unsigned i;
> >   	u32 base, limit, high;
> > -	struct resource *res, *conflict;
> >   	struct pci_dev *other;
> > +	struct resource *res;
> > +	unsigned i;
> > +	int r;
> >   
> >   	if (!(pci_probe & PCI_BIG_ROOT_WINDOW))
> >   		return;
> > @@ -702,19 +703,17 @@ static void pci_amd_enable_64bit_bar(struct pci_dev *dev)
> >   	if (!res)
> >   		return;
> >   
> > +	/* Allocate a 256GB window directly below the 0xfd00000000 hw limit */
> >   	res->name = "PCI Bus 0000:00";
> >   	res->flags = IORESOURCE_PREFETCH | IORESOURCE_MEM |
> >   		IORESOURCE_MEM_64 | IORESOURCE_WINDOW;
> > -	res->start = 0x100000000ull;
> > +	res->start = 0xbd00000000ull;
> >   	res->end = 0xfd00000000ull - 1;
> >   
> > -	/* Just grab the free area behind system memory for this */
> > -	while ((conflict = request_resource_conflict(&iomem_resource, res))) {
> > -		if (conflict->end >= res->end) {
> > -			kfree(res);
> > -			return;
> > -		}
> > -		res->start = conflict->end + 1;
> > +	r = request_resource(&iomem_resource, res);
> > +	if (r) {
> > +		kfree(res);
> > +		return;
> >   	}
> >   
> >   	dev_info(&dev->dev, "adding root bus resource %pR\n", res);
> > --
> > 2.11.0