On 3/7/2017 8:59 AM, Borislav Petkov wrote:
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...
I'll take a look at what it takes to consolidate these with a pre-patch.
Then I'll add the new support.
Thanks,
Tom
