linux-kernel - [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted

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Message-Id: <1673559753-94403-7-git-send-email-mikelley@microsoft.com>
Date:   Thu, 12 Jan 2023 13:42:25 -0800
From:   Michael Kelley <mikelley@...rosoft.com>
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Cc:     mikelley@...rosoft.com
Subject: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted

In a AMD SEV-SNP VM using vTOM, devices in MMIO space may be provided by
the paravisor and need to be mapped as encrypted.  Provide a function
for the hypervisor to specify the address range for such devices.
In __ioremap_caller(), map addresses in this range as encrypted.

Only a single range is supported. If multiple devices need to be
mapped encrypted, the paravisor must place them within the single
contiguous range.

Signed-off-by: Michael Kelley <mikelley@...rosoft.com>
---
 arch/x86/include/asm/io.h |  2 ++
 arch/x86/mm/ioremap.c     | 27 ++++++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index e902564..72eb366 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -169,6 +169,8 @@ static inline unsigned int isa_virt_to_bus(volatile void *address)
 }
 #define isa_bus_to_virt		phys_to_virt
 
+extern void ioremap_set_encrypted_range(resource_size_t addr, unsigned long size);
+
 /*
  * The default ioremap() behavior is non-cached; if you need something
  * else, you probably want one of the following.
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 6453fba..8db5846 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -37,6 +37,10 @@ struct ioremap_desc {
 	unsigned int flags;
 };
 
+/* Range of "other" addresses to treat as encrypted when remapping */
+resource_size_t other_encrypted_start;
+resource_size_t other_encrypted_end;
+
 /*
  * Fix up the linear direct mapping of the kernel to avoid cache attribute
  * conflicts.
@@ -108,14 +112,35 @@ static unsigned int __ioremap_check_encrypted(struct resource *res)
 }
 
 /*
+ * Allow a hypervisor to specify an additional range of addresses to
+ * treat as encrypted when remapping.
+ */
+void ioremap_set_encrypted_range(resource_size_t addr, unsigned long size)
+{
+	other_encrypted_start = addr;
+	other_encrypted_end = addr + size - 1;
+}
+
+/*
  * The EFI runtime services data area is not covered by walk_mem_res(), but must
- * be mapped encrypted when SEV is active.
+ * be mapped encrypted when SEV is active. Also check the hypervisor specified
+ * "other" address range to treat as encrypted.
  */
 static void __ioremap_check_other(resource_size_t addr, struct ioremap_desc *desc)
 {
 	if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
 		return;
 
+	/*
+	 * Check for an address within the "other" encrypted address range. If such
+	 * a range is set, it must include the entire space used by the device,
+	 * so we don't need to deal with a partial fit.
+	 */
+	if ((addr >= other_encrypted_start) && (addr <= other_encrypted_end)) {
+		desc->flags |= IORES_MAP_ENCRYPTED;
+		return;
+	}
+
 	if (!IS_ENABLED(CONFIG_EFI))
 		return;
 
-- 
1.8.3.1