Re: [PATCH 2/2] x86/PCI: limit the size of the 64bit window to 256GB v2

[Bjorn Helgaas]

On Wed, Jan 10, 2018 at 07:14:56PM +0100, Christian König wrote:
> Am 10.01.2018 um 19:02 schrieb Bjorn Helgaas:
> >[+cc linux-pci, previous cc list]
> >
> >On Wed, Jan 10, 2018 at 01:25:51PM +0100, Christian König 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.
> >>
> >>v2: cleanup code a bit more, update comment and explain the hw limit
> >Fixes a silent reboot loop reported by Aaro Koskinen
> ><aaro.koskinen@xxxxxx> on an AMD-based MSI MS-7699/760GA-P43(FX)
> >system.
> >
> >Link: https://lkml.kernel.org/r/20180105220412.fzpwqe4zljdawr36@xxxxxxxxxxxxxxxxxxxxxxxxx
> >Reported-by: Aaro Koskinen <aaro.koskinen@xxxxxx>
> >
> >>Signed-off-by: Christian König <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 */
> >Can you include a citation for the hardware limit in the changelog?
> >I'll try to dig it up myself if you don't beat me to it.
> 
> Sure, no problem. The first one in the series is ok as it is?

Yeah, I think so, although it would be good to add doc as Randy suggests.
Can you cc the folks involved (in particular, linux-pci) next time, too?

> >>  	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
> >>
>