On 8/1/2017 11:02 PM, Borislav Petkov wrote:
On Mon, Jul 24, 2017 at 02:07:51PM -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>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
arch/x86/mm/ioremap.c | 28 ++++++++++++++++++++++++++++
include/linux/ioport.h | 3 +++
kernel/resource.c | 17 +++++++++++++++++
3 files changed, 48 insertions(+)
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index c0be7cf..7b27332 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -69,6 +69,26 @@ static int __ioremap_check_ram(unsigned long start_pfn, unsigned long nr_pages,
return 0;
}
+static int __ioremap_res_desc_other(struct resource *res, void *arg)
+{
+ return (res->desc != IORES_DESC_NONE);
+}
+
+/*
+ * This function returns true if the target memory is marked as
+ * IORESOURCE_MEM and IORESOURCE_BUSY and described as other than
+ * IORES_DESC_NONE (e.g. IORES_DESC_ACPI_TABLES).
+ */
+static bool __ioremap_check_if_mem(resource_size_t addr, unsigned long size)
+{
+ u64 start, end;
+
+ start = (u64)addr;
+ end = start + size - 1;
+
+ return (walk_mem_res(start, end, NULL, __ioremap_res_desc_other) == 1);
+}
+
/*
* Remap an arbitrary physical address space into the kernel virtual
* address space. It transparently creates kernel huge I/O mapping when
@@ -146,7 +166,15 @@ 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() && __ioremap_check_if_mem(phys_addr, size))
+ prot = pgprot_encrypted(prot);
Hmm, so this function already does walk_system_ram_range() a bit
earlier and now on SEV systems we're going to do it again. Can we make
walk_system_ram_range() return a distinct value for SEV systems and act
accordingly in __ioremap_caller() instead of repeating the operation?
It looks to me like we could...
Let me look into this. I can probably come up with something that does
the walk once.
Thanks,
Tom
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