[Part1 PATCH v6 10/17] x86/mm, resource: Use PAGE_KERNEL protection for ioremap of memory pages

[Brijesh Singh]

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.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Laura Abbott <labbott@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: "JÃrÃme Glisse" <jglisse@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
---
 arch/x86/mm/ioremap.c  | 79 ++++++++++++++++++++++++++++++++++++++++++--------
 include/linux/ioport.h |  3 ++
 kernel/resource.c      | 19 ++++++++++++
 3 files changed, 89 insertions(+), 12 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 52cc0f4ed494..6e4573b1da34 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -27,6 +27,11 @@
 
 #include "physaddr.h"
 
+struct ioremap_mem_flags {
+	bool system_ram;
+	bool desc_other;
+};
+
 /*
  * Fix up the linear direct mapping of the kernel to avoid cache attribute
  * conflicts.
@@ -56,17 +61,59 @@ int ioremap_change_attr(unsigned long vaddr, unsigned long size,
 	return err;
 }
 
-static int __ioremap_check_ram(unsigned long start_pfn, unsigned long nr_pages,
-			       void *arg)
+static bool __ioremap_check_ram(struct resource *res)
 {
+	unsigned long start_pfn, stop_pfn;
 	unsigned long i;
 
-	for (i = 0; i < nr_pages; ++i)
-		if (pfn_valid(start_pfn + i) &&
-		    !PageReserved(pfn_to_page(start_pfn + i)))
-			return 1;
+	if ((res->flags & IORESOURCE_SYSTEM_RAM) != IORESOURCE_SYSTEM_RAM)
+		return false;
 
-	return 0;
+	start_pfn = (res->start + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	stop_pfn = (res->end + 1) >> PAGE_SHIFT;
+	if (stop_pfn > start_pfn) {
+		for (i = 0; i < (stop_pfn - start_pfn); ++i)
+			if (pfn_valid(start_pfn + i) &&
+			    !PageReserved(pfn_to_page(start_pfn + i)))
+				return true;
+	}
+
+	return false;
+}
+
+static int __ioremap_check_desc_other(struct resource *res)
+{
+	return (res->desc != IORES_DESC_NONE);
+}
+
+static int __ioremap_res_check(struct resource *res, void *arg)
+{
+	struct ioremap_mem_flags *flags = arg;
+
+	if (!flags->system_ram)
+		flags->system_ram = __ioremap_check_ram(res);
+
+	if (!flags->desc_other)
+		flags->desc_other = __ioremap_check_desc_other(res);
+
+	return flags->system_ram && flags->desc_other;
+}
+
+/*
+ * To avoid multiple resource walks, this function walks resources marked as
+ * IORESOURCE_MEM and IORESOURCE_BUSY and looking for system RAM and/or a
+ * resource described not as IORES_DESC_NONE (e.g. IORES_DESC_ACPI_TABLES).
+ */
+static void __ioremap_check_mem(resource_size_t addr, unsigned long size,
+				struct ioremap_mem_flags *flags)
+{
+	u64 start, end;
+
+	start = (u64)addr;
+	end = start + size - 1;
+	memset(flags, 0, sizeof(*flags));
+
+	walk_mem_res(start, end, flags, __ioremap_res_check);
 }
 
 /*
@@ -87,9 +134,10 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
 		unsigned long size, enum page_cache_mode pcm, void *caller)
 {
 	unsigned long offset, vaddr;
-	resource_size_t pfn, last_pfn, last_addr;
+	resource_size_t last_addr;
 	const resource_size_t unaligned_phys_addr = phys_addr;
 	const unsigned long unaligned_size = size;
+	struct ioremap_mem_flags mem_flags;
 	struct vm_struct *area;
 	enum page_cache_mode new_pcm;
 	pgprot_t prot;
@@ -108,13 +156,12 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
 		return NULL;
 	}
 
+	__ioremap_check_mem(phys_addr, size, &mem_flags);
+
 	/*
 	 * Don't allow anybody to remap normal RAM that we're using..
 	 */
-	pfn      = phys_addr >> PAGE_SHIFT;
-	last_pfn = last_addr >> PAGE_SHIFT;
-	if (walk_system_ram_range(pfn, last_pfn - pfn + 1, NULL,
-					  __ioremap_check_ram) == 1) {
+	if (mem_flags.system_ram) {
 		WARN_ONCE(1, "ioremap on RAM at %pa - %pa\n",
 			  &phys_addr, &last_addr);
 		return NULL;
@@ -146,7 +193,15 @@ 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() && mem_flags.desc_other)
+		prot = pgprot_encrypted(prot);
+
 	switch (pcm) {
 	case _PAGE_CACHE_MODE_UC:
 	default:
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 617d8a2aac67..c04d584ab5a1 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -270,6 +270,9 @@ extern int
 walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
 		void *arg, int (*func)(unsigned long, unsigned long, void *));
 extern int
+walk_mem_res(u64 start, u64 end, void *arg,
+	     int (*func)(struct resource *, void *));
+extern int
 walk_system_ram_res(u64 start, u64 end, void *arg,
 		    int (*func)(struct resource *, void *));
 extern int
diff --git a/kernel/resource.c b/kernel/resource.c
index 8430042fa77b..54ba6de3757c 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -397,6 +397,8 @@ static int find_next_iomem_res(struct resource *res, unsigned long desc,
 		res->start = p->start;
 	if (res->end > p->end)
 		res->end = p->end;
+	res->flags = p->flags;
+	res->desc = p->desc;
 	return 0;
 }
 
@@ -467,6 +469,23 @@ int walk_system_ram_res(u64 start, u64 end, void *arg,
 				     arg, func);
 }
 
+/*
+ * This function calls the @func callback against all memory ranges, which
+ * are ranges marked as IORESOURCE_MEM and IORESOUCE_BUSY.
+ */
+int walk_mem_res(u64 start, u64 end, void *arg,
+		 int (*func)(struct resource *, void *))
+{
+	struct resource res;
+
+	res.start = start;
+	res.end = end;
+	res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+
+	return __walk_iomem_res_desc(&res, IORES_DESC_NONE, true,
+				     arg, func);
+}
+
 #if !defined(CONFIG_ARCH_HAS_WALK_MEMORY)
 
 /*
-- 
2.9.5