ArmVirtPkg/ArmPlatformLibQemu: Enable early ID map on EL2+VHE

When booting at EL2, enable VHE if available so that the early ID map can be enabled as well. This gets rid of any memory accesses (reads or writes) before the MMU and caches are enabled. Signed-off-by: Ard Biesheuvel <[email protected]>
tianocore · Dec 5, 2024 · 47e28a6 · 47e28a6
1 parent 793f4d2
commit 47e28a6
Showing 1 changed file with 13 additions and 1 deletion.
diff --git a/ArmVirtPkg/Library/ArmPlatformLibQemu/AArch64/ArmPlatformHelper.S b/ArmVirtPkg/Library/ArmPlatformLibQemu/AArch64/ArmPlatformHelper.S
@@ -40,6 +40,9 @@
  .set    sctlrval, SCTLR_ELx_M | SCTLR_ELx_C | SCTLR_ELx_SA | SCTLR_EL1_ITD | SCTLR_EL1_SED
  .set    sctlrval, sctlrval | SCTLR_ELx_I | SCTLR_EL1_SPAN | SCTLR_EL1_RES1
 
+ .set    ID_AA64MMFR1_VH_MASK,  0xf << 8
+ .set    HCR_EL2_E2H,           0x1 << 34
+
 
 ASM_FUNC(ArmPlatformPeiBootAction)
 #ifdef CAVIUM_ERRATUM_27456
@@ -58,8 +61,17 @@ ASM_FUNC(ArmPlatformPeiBootAction)
   b.eq   0f
 #endif
   mrs    x0, CurrentEL           // check current exception level
-  tbnz   x0, #3, 0f              // omit early ID map if above EL1
+  tbz    x0, #3, .Learly_idmap   // use early ID map if at EL1
+  mrs    x0, id_aa64mmfr1_el1    // otherwise, check for VHE support
+  tst    x0, #ID_AA64MMFR1_VH_MASK
+  b.eq   0f
+
+  mrs    x0, hcr_el2             // Enable VHE support
+  orr    x0, x0, #HCR_EL2_E2H
+  msr    hcr_el2, x0
+  isb
 
+.Learly_idmap:
   mov_i  x0, mairval
   mov_i  x1, tcrval
   adrp   x2, idmap