[kvm-unit-tests PATCH v5 4/8] x86: Improve set_mmu_range() to implement npt

[Manali Shukla <manali.shukla@xxxxxxx>]

Modify setup_mmu_range() to implement nested page table dynamically by setting
PT_USER_MASK bit for all NPT pages because any nested page table accesses
performed by the MMU are treated as user accesses.

Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Manali Shukla <manali.shukla@xxxxxxx>
---
 lib/x86/vm.c | 25 +++++++++++++++++++++----
 lib/x86/vm.h |  8 ++++++++
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/lib/x86/vm.c b/lib/x86/vm.c
index 25a4f5f..46c36e5 100644
--- a/lib/x86/vm.c
+++ b/lib/x86/vm.c
@@ -140,16 +140,33 @@ bool any_present_pages(pgd_t *cr3, void *virt, size_t len)
 	return false;
 }
 
-static void setup_mmu_range(pgd_t *cr3, phys_addr_t start, size_t len)
+void __setup_mmu_range(pgd_t *cr3, phys_addr_t start, size_t len,
+		       unsigned long long mmu_flags)
 {
+	u64 orig_opt_mask = pte_opt_mask;
 	u64 max = (u64)len + (u64)start;
 	u64 phys = start;
 
-	while (phys + LARGE_PAGE_SIZE <= max) {
-		install_large_page(cr3, phys, (void *)(ulong)phys);
-		phys += LARGE_PAGE_SIZE;
+	/*
+	 * Allocate 4k pages only for nested page table, PT_USER_MASK needs to
+	 * be enabled only for nested pages.
+	 */
+	if (mmu_flags & IS_NESTED_MMU)
+		pte_opt_mask |= PT_USER_MASK;
+
+	if (mmu_flags & USE_HUGEPAGES) {
+		while (phys + LARGE_PAGE_SIZE <= max) {
+			install_large_page(cr3, phys, (void *)(ulong)phys);
+			phys += LARGE_PAGE_SIZE;
+		}
 	}
 	install_pages(cr3, phys, max - phys, (void *)(ulong)phys);
+
+	pte_opt_mask = orig_opt_mask;
+}
+
+static inline void setup_mmu_range(pgd_t *cr3, phys_addr_t start, size_t len) {
+	__setup_mmu_range(cr3, start, len, USE_HUGEPAGES);
 }
 
 static void set_additional_vcpu_vmregs(struct vm_vcpu_info *info)
diff --git a/lib/x86/vm.h b/lib/x86/vm.h
index 4c6dff9..2df19e3 100644
--- a/lib/x86/vm.h
+++ b/lib/x86/vm.h
@@ -4,6 +4,10 @@
 #include "processor.h"
 #include "asm/page.h"
 #include "asm/io.h"
+#include "asm/bitops.h"
+
+#define IS_NESTED_MMU BIT(0)
+#define USE_HUGEPAGES BIT(1)
 
 void setup_5level_page_table(void);
 
@@ -37,6 +41,10 @@ pteval_t *install_pte(pgd_t *cr3,
 pteval_t *install_large_page(pgd_t *cr3, phys_addr_t phys, void *virt);
 void install_pages(pgd_t *cr3, phys_addr_t phys, size_t len, void *virt);
 bool any_present_pages(pgd_t *cr3, void *virt, size_t len);
+void set_pte_opt_mask(void);
+void reset_pte_opt_mask(void);
+void __setup_mmu_range(pgd_t *cr3, phys_addr_t start, size_t len,
+		       unsigned long long mmu_flags);
 
 static inline void *current_page_table(void)
 {
-- 
2.30.2