[Qemu-devel] [RFC PATCH v1 18/22] i386: clear C-bit in SEV guest page table walk

[Brijesh Singh <brijesh.singh@amd.com>]

In SEV-enabled guest the physical addresses in page table will
have C-bit set, we need to clear the C-bit when walking the page table.
The C-bit position should be available in cpuid Fn8000_001f[EBX]

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 target-i386/helper.c  |   36 +++++++++++++++++++++++++++++-------
 target-i386/monitor.c |   32 ++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 7 deletions(-)

diff --git a/target-i386/helper.c b/target-i386/helper.c
index 1c250b8..a9d8aef 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -1006,6 +1006,22 @@ do_check_protect_pse36:
     return 1;
 }
 
+static uint64_t get_me_mask(void)
+{
+    uint64_t me_mask = 0;
+
+    /* In SEV guest page tables addresses will have memory encryption bit set,
+     * C-bit should be cleared while doing the page table walk.
+     */
+    if (kvm_sev_enabled()) {
+        uint32_t pos;
+        pos = kvm_arch_get_supported_cpuid(kvm_state, 0x8000001f, 0, R_EBX);
+        me_mask = (1UL << pos);
+    }
+
+    return ~me_mask;
+}
+
 hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
 {
     X86CPU *cpu = X86_CPU(cs);
@@ -1014,6 +1030,12 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
     uint64_t pte;
     uint32_t page_offset;
     int page_size;
+    uint64_t me_mask;
+
+    me_mask = get_me_mask();
+
+    /* In SEV guest, CR3 will have memory encryption bit set, clear it */
+    env->cr[3] &= me_mask;
 
     if (!(env->cr[0] & CR0_PG_MASK)) {
         pte = addr & env->a20_mask;
@@ -1034,13 +1056,13 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
             }
             pml4e_addr = ((env->cr[3] & ~0xfff) + (((addr >> 39) & 0x1ff) << 3)) &
                 env->a20_mask;
-            pml4e = x86_ldq_phys(cs, pml4e_addr);
+            pml4e = x86_ldq_phys(cs, pml4e_addr) & me_mask;
             if (!(pml4e & PG_PRESENT_MASK)) {
                 return -1;
             }
             pdpe_addr = ((pml4e & PG_ADDRESS_MASK) +
                          (((addr >> 30) & 0x1ff) << 3)) & env->a20_mask;
-            pdpe = x86_ldq_phys(cs, pdpe_addr);
+            pdpe = x86_ldq_phys(cs, pdpe_addr) & me_mask;
             if (!(pdpe & PG_PRESENT_MASK)) {
                 return -1;
             }
@@ -1055,14 +1077,14 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
         {
             pdpe_addr = ((env->cr[3] & ~0x1f) + ((addr >> 27) & 0x18)) &
                 env->a20_mask;
-            pdpe = x86_ldq_phys(cs, pdpe_addr);
+            pdpe = x86_ldq_phys(cs, pdpe_addr) & me_mask;
             if (!(pdpe & PG_PRESENT_MASK))
                 return -1;
         }
 
         pde_addr = ((pdpe & PG_ADDRESS_MASK) +
                     (((addr >> 21) & 0x1ff) << 3)) & env->a20_mask;
-        pde = x86_ldq_phys(cs, pde_addr);
+        pde = x86_ldq_phys(cs, pde_addr) & me_mask;
         if (!(pde & PG_PRESENT_MASK)) {
             return -1;
         }
@@ -1075,7 +1097,7 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
             pte_addr = ((pde & PG_ADDRESS_MASK) +
                         (((addr >> 12) & 0x1ff) << 3)) & env->a20_mask;
             page_size = 4096;
-            pte = x86_ldq_phys(cs, pte_addr);
+            pte = x86_ldq_phys(cs, pte_addr) & me_mask;
         }
         if (!(pte & PG_PRESENT_MASK)) {
             return -1;
@@ -1085,7 +1107,7 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
 
         /* page directory entry */
         pde_addr = ((env->cr[3] & ~0xfff) + ((addr >> 20) & 0xffc)) & env->a20_mask;
-        pde = x86_ldl_phys(cs, pde_addr);
+        pde = x86_ldl_phys(cs, pde_addr) & me_mask;
         if (!(pde & PG_PRESENT_MASK))
             return -1;
         if ((pde & PG_PSE_MASK) && (env->cr[4] & CR4_PSE_MASK)) {
@@ -1094,7 +1116,7 @@ hwaddr x86_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
         } else {
             /* page directory entry */
             pte_addr = ((pde & ~0xfff) + ((addr >> 10) & 0xffc)) & env->a20_mask;
-            pte = x86_ldl_phys(cs, pte_addr);
+            pte = x86_ldl_phys(cs, pte_addr) & me_mask;
             if (!(pte & PG_PRESENT_MASK)) {
                 return -1;
             }
diff --git a/target-i386/monitor.c b/target-i386/monitor.c
index 47d3c2d..94e6c70 100644
--- a/target-i386/monitor.c
+++ b/target-i386/monitor.c
@@ -54,6 +54,22 @@ static void print_pte(Monitor *mon, hwaddr addr,
                    pte & PG_RW_MASK ? 'W' : '-');
 }
 
+static uint64_t get_me_mask(void)
+{
+    uint64_t me_mask = 0;
+
+    /* In SEV guest page tables addresses will have memory encryption bit set,
+     * C-bit should be cleared while doing the page table walk.
+     */
+    if (kvm_sev_enabled()) {
+        uint32_t pos;
+        pos = kvm_arch_get_supported_cpuid(kvm_state, 0x8000001f, 0, R_EBX);
+        me_mask = (1UL << pos);
+    }
+
+    return ~me_mask;
+}
+
 static void tlb_info_32(Monitor *mon, CPUArchState *env)
 {
     unsigned int l1, l2;
@@ -127,15 +143,21 @@ static void tlb_info_64(Monitor *mon, CPUArchState *env)
     uint64_t l1, l2, l3, l4;
     uint64_t pml4e, pdpe, pde, pte;
     uint64_t pml4_addr, pdp_addr, pd_addr, pt_addr;
+    uint64_t me_mask;
+
+    me_mask = get_me_mask();
 
     pml4_addr = env->cr[3] & 0x3fffffffff000ULL;
+    pml4_addr &= me_mask;
     for (l1 = 0; l1 < 512; l1++) {
         cpu_physical_memory_read_debug(pml4_addr + l1 * 8, &pml4e, 8);
+        pml4e &= me_mask;
         pml4e = le64_to_cpu(pml4e);
         if (pml4e & PG_PRESENT_MASK) {
             pdp_addr = pml4e & 0x3fffffffff000ULL;
             for (l2 = 0; l2 < 512; l2++) {
                 cpu_physical_memory_read_debug(pdp_addr + l2 * 8, &pdpe, 8);
+                pdpe &= me_mask;
                 pdpe = le64_to_cpu(pdpe);
                 if (pdpe & PG_PRESENT_MASK) {
                     if (pdpe & PG_PSE_MASK) {
@@ -147,6 +169,7 @@ static void tlb_info_64(Monitor *mon, CPUArchState *env)
                         for (l3 = 0; l3 < 512; l3++) {
                             cpu_physical_memory_read_debug(pd_addr + l3 * 8,
                                     &pde, 8);
+                            pde &= me_mask;
                             pde = le64_to_cpu(pde);
                             if (pde & PG_PRESENT_MASK) {
                                 if (pde & PG_PSE_MASK) {
@@ -160,6 +183,7 @@ static void tlb_info_64(Monitor *mon, CPUArchState *env)
                                         cpu_physical_memory_read_debug(pt_addr
                                                                  + l4 * 8,
                                                                  &pte, 8);
+                                        pte &= me_mask;
                                         pte = le64_to_cpu(pte);
                                         if (pte & PG_PRESENT_MASK) {
                                             print_pte(mon, (l1 << 39) +
@@ -331,18 +355,24 @@ static void mem_info_64(Monitor *mon, CPUArchState *env)
     uint64_t l1, l2, l3, l4;
     uint64_t pml4e, pdpe, pde, pte;
     uint64_t pml4_addr, pdp_addr, pd_addr, pt_addr, start, end;
+    uint64_t me_mask;
+
+    me_mask = get_me_mask();
 
     pml4_addr = env->cr[3] & 0x3fffffffff000ULL;
+    pml4_addr &= me_mask;
     last_prot = 0;
     start = -1;
     for (l1 = 0; l1 < 512; l1++) {
         cpu_physical_memory_read_debug(pml4_addr + l1 * 8, &pml4e, 8);
+        pml4e &= me_mask;
         pml4e = le64_to_cpu(pml4e);
         end = l1 << 39;
         if (pml4e & PG_PRESENT_MASK) {
             pdp_addr = pml4e & 0x3fffffffff000ULL;
             for (l2 = 0; l2 < 512; l2++) {
                 cpu_physical_memory_read_debug(pdp_addr + l2 * 8, &pdpe, 8);
+                pdpe &= me_mask;
                 pdpe = le64_to_cpu(pdpe);
                 end = (l1 << 39) + (l2 << 30);
                 if (pdpe & PG_PRESENT_MASK) {
@@ -356,6 +386,7 @@ static void mem_info_64(Monitor *mon, CPUArchState *env)
                         for (l3 = 0; l3 < 512; l3++) {
                             cpu_physical_memory_read_debug(pd_addr + l3 * 8,
                                     &pde, 8);
+                            pde &= me_mask;
                             pde = le64_to_cpu(pde);
                             end = (l1 << 39) + (l2 << 30) + (l3 << 21);
                             if (pde & PG_PRESENT_MASK) {
@@ -370,6 +401,7 @@ static void mem_info_64(Monitor *mon, CPUArchState *env)
                                         cpu_physical_memory_read_debug(pt_addr
                                                                  + l4 * 8,
                                                                  &pte, 8);
+                                        pte &= me_mask;
                                         pte = le64_to_cpu(pte);
                                         end = (l1 << 39) + (l2 << 30) +
                                             (l3 << 21) + (l4 << 12);