On Wed, 2015-09-02 at 08:39 -0700, Nishanth Aravamudan wrote:
> On 02.09.2015 [19:00:31 +1000], Alexey Kardashevskiy wrote:
> > On 09/02/2015 11:11 AM, Nishanth Aravamudan wrote:
> > >diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c
> > >b/arch/powerpc/platforms/powernv/pci-ioda.c
> > >index 85cbc96eff6c..0d7967e31169 100644
> > >--- a/arch/powerpc/platforms/powernv/pci-ioda.c
> > >+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> > >@@ -2077,10 +2077,17 @@ static long
> > >pnv_pci_ioda2_setup_default_config(struct pnv_ioda_pe *pe)
> > > {
> > > struct iommu_table *tbl = NULL;
> > > long rc;
> > >+ /*
> > >+ * In memory constrained environments, e.g. kdump kernel, the
> > >+ * DMA window can be larger than available memory, which will
> > >+ * cause errors later.
> > >+ */
> > >+ __u64 window_size =
> >
> > I asked for "const __u64" ;)
>
> I knew I'd forget something!
Nish! In future please send a reply with the above comment, and then the v2 as
a separate mail, otherwise I have to manually edit out your comment when
applying.
> When attempting to kdump with the 4.2 kernel, we see for each PCI
> device:
>
> pci 0003:01 : [PE# 000] Assign DMA32 space
> pci 0003:01 : [PE# 000] Setting up 32-bit TCE table at 0..80000000
> pci 0003:01 : [PE# 000] Failed to create 32-bit TCE table, err -22
> PCI: Domain 0004 has 8 available 32-bit DMA segments
> PCI: 4 PE# for a total weight of 70
> pci 0004:01 : [PE# 002] Assign DMA32 space
> pci 0004:01 : [PE# 002] Setting up 32-bit TCE table at 0..80000000
> pci 0004:01 : [PE# 002] Failed to create 32-bit TCE table, err -22
> pci 0004:0d : [PE# 005] Assign DMA32 space
> pci 0004:0d : [PE# 005] Setting up 32-bit TCE table at 0..80000000
> pci 0004:0d : [PE# 005] Failed to create 32-bit TCE table, err -22
> pci 0004:0e : [PE# 006] Assign DMA32 space
> pci 0004:0e : [PE# 006] Setting up 32-bit TCE table at 0..80000000
> pci 0004:0e : [PE# 006] Failed to create 32-bit TCE table, err -22
> pci 0004:10 : [PE# 008] Assign DMA32 space
> pci 0004:10 : [PE# 008] Setting up 32-bit TCE table at 0..80000000
> pci 0004:10 : [PE# 008] Failed to create 32-bit TCE table, err -22
>
> and eventually the kdump kernel fails to boot as none of the PCI devices
> (including the disk controller) are successfully initialized.
>
> The EINVAL response is because the DMA window (the 2GB base window) is
> larger than the kdump kernel's reserved memory (crashkernel=, in this
> case specified to be 1024M). The check in question,
>
> if ((window_size > memory_hotplug_max()) || !is_power_of_2(window_size))
>
> is a valid sanity check for pnv_pci_ioda2_table_alloc_pages(), so adjust
> the caller to pass in a smaller window size if our maximum memory value
> is smaller than the DMA window.
>
> After this change, the PCI devices successfully set up the 32-bit TCE
> table and kdump succeeds.
>
> The problem was seen on a Firestone machine originally.
>
> Fixes: aca6913f5551 ("powerpc/powernv/ioda2: Introduce helpers to allocate
> TCE pages")
That went into 4.2, so should this have a:
Cc: sta...@vger.kernel.org # 4.2
?
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c
> b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 85cbc96eff6c..e51aff01a218 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -2077,10 +2077,17 @@ static long pnv_pci_ioda2_setup_default_config(struct
> pnv_ioda_pe *pe)
> {
> struct iommu_table *tbl = NULL;
> long rc;
> + /*
> + * In memory constrained environments, e.g. kdump kernel, the
> + * DMA window can be larger than available memory, which will
> + * cause errors later.
> + */
> + const __u64 window_size =
Why is this using __u64 and not u64, it's not exported to userspace.
It looks like pnv_pci_ioda2_create_table() uses __u64, but there's no reason
for that AFAICS either. And yes I did commit it so it's my fault :)
I'll fix this up to use u64.
cheers
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