* Igor Mammedov <[email protected]> wrote:
> when memory hotplug enabled system is booted with less
> than 4GB of RAM and then later more RAM is hotplugged
> 32-bit devices stop functioning with following error:
>
> nommu_map_single: overflow 327b4f8c0+1522 of device mask ffffffff
>
> the reason for this is that if x86_64 system were booted
> with RAM less than 4GB, it doesn't enable SWIOTLB and
> when memory is hotplugged beyond MAX_DMA32_PFN, devices
> that expect 32-bit addresses can't handle 64-bit addresses.
>
> Fix it by tracking max possible PFN when parsing
> memory affinity structures from SRAT ACPI table and
> enable SWIOTLB if there is hotpluggable memory
> regions beyond MAX_DMA32_PFN.
>
> It fixes KVM guests when they use emulated devices
> (reproduces with ata_piix, e1000 and usb devices,
> RHBZ: 1275941, 1275977, 1271527)
> It also fixes the HyperV, VMWare with emulated devices
> which are affected by this issue as well.
>
> Signed-off-by: Igor Mammedov <[email protected]>
> ---
> arch/x86/kernel/pci-swiotlb.c | 2 +-
> arch/x86/mm/srat.c | 3 +++
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
> index adf0392..7c577a1 100644
> --- a/arch/x86/kernel/pci-swiotlb.c
> +++ b/arch/x86/kernel/pci-swiotlb.c
> @@ -88,7 +88,7 @@ int __init pci_swiotlb_detect_4gb(void)
> {
> /* don't initialize swiotlb if iommu=off (no_iommu=1) */
> #ifdef CONFIG_X86_64
> - if (!no_iommu && max_pfn > MAX_DMA32_PFN)
> + if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN)
> swiotlb = 1;
Ok, this series looks a lot better!
> #endif
> return swiotlb;
> diff --git a/arch/x86/mm/srat.c b/arch/x86/mm/srat.c
> index c2aea63..a26bdbe 100644
> --- a/arch/x86/mm/srat.c
> +++ b/arch/x86/mm/srat.c
> @@ -203,6 +203,9 @@ acpi_numa_memory_affinity_init(struct
> acpi_srat_mem_affinity *ma)
> pr_warn("SRAT: Failed to mark hotplug range [mem
> %#010Lx-%#010Lx] in memblock\n",
> (unsigned long long)start, (unsigned long long)end - 1);
>
> + if (max_possible_pfn < PFN_UP(end - 1))
> + max_possible_pfn = PFN_UP(end - 1);
Small nit, why not write this as something like:
max_possible_pfn = max(max_possible_pfn, PFN_UP(end - 1));
?
I'd also move this second hunk to the first patch, because logically it belongs
there (or into a third patch).
Thanks,
Ingo
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