[PATCH Part2 v5 04/45] x86/sev: Add RMP entry lookup helpers

Brijesh Singh
2021-08-20T16:00:09Z

The snp_lookup_page_in_rmptable() can be used by the host to read the RMP
entry for a given page. The RMP entry format is documented in AMD PPR, see
https://bugzilla.kernel.org/attachment.cgi?id=296015.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/include/asm/sev.h | 27 ++++++++++++++++++++++++
arch/x86/kernel/sev.c | 43 ++++++++++++++++++++++++++++++++++++++
include/linux/sev.h | 30 ++++++++++++++++++++++++++
3 files changed, 100 insertions(+)
create mode 100644 include/linux/sev.h

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index a5f0a1c3ccbe..5b1a6a075c47 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -9,6 +9,7 @@
#define __ASM_ENCRYPTED_STATE_H

#include <linux/types.h>
+#include <linux/sev.h>
#include <asm/insn.h>
#include <asm/sev-common.h>
#include <asm/bootparam.h>
@@ -77,6 +78,32 @@ extern bool handle_vc_boot_ghcb(struct pt_regs *regs);

/* RMP page size */
#define RMP_PG_SIZE_4K 0
+#define RMP_TO_X86_PG_LEVEL(level) (((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M)
+
+/*
+ * The RMP entry format is not architectural. The format is defined in PPR
+ * Family 19h Model 01h, Rev B1 processor.
+ */
+struct __packed rmpentry {
+ union {
+ struct {
+ u64 assigned : 1,
+ pagesize : 1,
+ immutable : 1,
+ rsvd1 : 9,
+ gpa : 39,
+ asid : 10,
+ vmsa : 1,
+ validated : 1,
+ rsvd2 : 1;
+ } info;
+ u64 low;
+ };
+ u64 high;
+};
+
+#define rmpentry_assigned(x) ((x)->info.assigned)
+#define rmpentry_pagesize(x) ((x)->info.pagesize)

#define RMPADJUST_VMSA_PAGE_BIT BIT(16)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 7936c8139c74..f383d2a89263 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -54,6 +54,8 @@
* bookkeeping, the range need to be added during the RMP entry lookup.
*/
#define RMPTABLE_CPU_BOOKKEEPING_SZ 0x4000
+#define RMPENTRY_SHIFT 8
+#define rmptable_page_offset(x) (RMPTABLE_CPU_BOOKKEEPING_SZ + (((unsigned long)x) >> RMPENTRY_SHIFT))

/* For early boot hypervisor communication in SEV-ES enabled guests */
static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE);
@@ -2376,3 +2378,44 @@ static int __init snp_rmptable_init(void)
* available after subsys_initcall().
*/
fs_initcall(snp_rmptable_init);
+
+static struct rmpentry *__snp_lookup_rmpentry(u64 pfn, int *level)
+{
+ unsigned long vaddr, paddr = pfn << PAGE_SHIFT;
+ struct rmpentry *entry, *large_entry;
+
+ if (!pfn_valid(pfn))
+ return ERR_PTR(-EINVAL);
+
+ if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+ return ERR_PTR(-ENXIO);
+
+ vaddr = rmptable_start + rmptable_page_offset(paddr);
+ if (unlikely(vaddr > rmptable_end))
+ return ERR_PTR(-ENXIO);
+
+ entry = (struct rmpentry *)vaddr;
+
+ /* Read a large RMP entry to get the correct page level used in RMP entry. */
+ vaddr = rmptable_start + rmptable_page_offset(paddr & PMD_MASK);
+ large_entry = (struct rmpentry *)vaddr;
+ *level = RMP_TO_X86_PG_LEVEL(rmpentry_pagesize(large_entry));
+
+ return entry;
+}
+
+/*
+ * Return 1 if the RMP entry is assigned, 0 if it exists but is not assigned,
+ * and -errno if there is no corresponding RMP entry.
+ */
+int snp_lookup_rmpentry(u64 pfn, int *level)
+{
+ struct rmpentry *e;
+
+ e = __snp_lookup_rmpentry(pfn, level);
+ if (IS_ERR(e))
+ return PTR_ERR(e);
+
+ return !!rmpentry_assigned(e);
+}
+EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
diff --git a/include/linux/sev.h b/include/linux/sev.h
new file mode 100644
index 000000000000..1a68842789e1
--- /dev/null
+++ b/include/linux/sev.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * AMD Secure Encrypted Virtualization
+ *
+ * Author: Brijesh Singh <brijesh.singh@amd.com>
+ */
+
+#ifndef __LINUX_SEV_H
+#define __LINUX_SEV_H
+
+/* RMUPDATE detected 4K page and 2MB page overlap. */
+#define RMPUPDATE_FAIL_OVERLAP 7
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+int snp_lookup_rmpentry(u64 pfn, int *level);
+int psmash(u64 pfn);
+int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable);
+int rmp_make_shared(u64 pfn, enum pg_level level);
+#else
+static inline int snp_lookup_rmpentry(u64 pfn, int *level) { return 0; }
+static inline int psmash(u64 pfn) { return -ENXIO; }
+static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid,
+ bool immutable)
+{
+ return -ENODEV;
+}
+static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; }
+
+#endif /* CONFIG_AMD_MEM_ENCRYPT */
+#endif /* __LINUX_SEV_H */
--
2.17.1