On Thu, Mar 02, 2017 at 10:13:32AM -0500, Brijesh Singh wrote:
> From: Tom Lendacky <thomas.lendacky@xxxxxxx>
>
> In order for memory pages to be properly mapped when SEV is active, we
> need to use the PAGE_KERNEL protection attribute as the base protection.
> This will insure that memory mapping of, e.g. ACPI tables, receives the
> proper mapping attributes.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> ---
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index c400ab5..481c999 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -151,7 +151,15 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
> pcm = new_pcm;
> }
>
> + /*
> + * If the page being mapped is in memory and SEV is active then
> + * make sure the memory encryption attribute is enabled in the
> + * resulting mapping.
> + */
> prot = PAGE_KERNEL_IO;
> + if (sev_active() && page_is_mem(pfn))
Hmm, a resource tree walk per ioremap call. This could get expensive for
ioremap-heavy workloads.
__ioremap_caller() gets called here during boot 55 times so not a whole
lot but I wouldn't be surprised if there were some nasty use cases which
ioremap a lot.
...
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 9b5f044..db56ba3 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -518,6 +518,46 @@ int __weak page_is_ram(unsigned long pfn)
> }
> EXPORT_SYMBOL_GPL(page_is_ram);
>
> +/*
> + * This function returns true if the target memory is marked as
> + * IORESOURCE_MEM and IORESOUCE_BUSY and described as other than
> + * IORES_DESC_NONE (e.g. IORES_DESC_ACPI_TABLES).
> + */
> +static int walk_mem_range(unsigned long start_pfn, unsigned long nr_pages)
> +{
> + struct resource res;
> + unsigned long pfn, end_pfn;
> + u64 orig_end;
> + int ret = -1;
> +
> + res.start = (u64) start_pfn << PAGE_SHIFT;
> + res.end = ((u64)(start_pfn + nr_pages) << PAGE_SHIFT) - 1;
> + res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> + orig_end = res.end;
> + while ((res.start < res.end) &&
> + (find_next_iomem_res(&res, IORES_DESC_NONE, true) >= 0)) {
> + pfn = (res.start + PAGE_SIZE - 1) >> PAGE_SHIFT;
> + end_pfn = (res.end + 1) >> PAGE_SHIFT;
> + if (end_pfn > pfn)
> + ret = (res.desc != IORES_DESC_NONE) ? 1 : 0;
> + if (ret)
> + break;
> + res.start = res.end + 1;
> + res.end = orig_end;
> + }
> + return ret;
> +}
So the relevant difference between this one and walk_system_ram_range()
is this:
- ret = (*func)(pfn, end_pfn - pfn, arg);
+ ret = (res.desc != IORES_DESC_NONE) ? 1 : 0;
so it seems to me you can have your own *func() pointer which does that
IORES_DESC_NONE comparison. And then you can define your own workhorse
__walk_memory_range() which gets called by both walk_mem_range() and
walk_system_ram_range() instead of almost duplicating them.
And looking at walk_system_ram_res(), that one looks similar too except
the pfn computation. But AFAICT the pfn/end_pfn things are computed from
res.start and res.end so it looks to me like all those three functions
are crying for unification...
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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