Merge branch kvm-arm64/s1ptw-write-fault into kvmarm-master/fixes

* kvm-arm64/s1ptw-write-fault:
  : .
  : Fix S1PTW fault handling that was until then always taken
  : as a write. From the cover letter:
  :
  : `Recent developments on the EFI front have resulted in guests that
  : simply won't boot if the page tables are in a read-only memslot and
  : that you're a bit unlucky in the way S2 gets paged in... The core
  : issue is related to the fact that we treat a S1PTW as a write, which
  : is close enough to what needs to be done. Until to get to RO memslots.
  :
  : The first patch fixes this and is definitely a stable candidate. It
  : splits the faulting of page tables in two steps (RO translation fault,
  : followed by a writable permission fault -- should it even happen).
  : The second one documents the slightly odd behaviour of PTW writes to
  : RO memslot, which do not result in a KVM_MMIO exit. The last patch is
  : totally optional, only tangentially related, and randomly repainting
  : stuff (maybe that's contagious, who knows)."
  :
  : .
  KVM: arm64: Convert FSC_* over to ESR_ELx_FSC_*
  KVM: arm64: Document the behaviour of S1PTW faults on RO memslots
  KVM: arm64: Fix S1PTW handling on RO memslots

Signed-off-by: Marc Zyngier <maz@kernel.org>

3 files changed, 39 insertions, 27 deletions

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 15b34fbfca66..206de10524e3 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -114,6 +114,15 @@
 #define ESR_ELx_FSC_ACCESS	(0x08)
 #define ESR_ELx_FSC_FAULT	(0x04)
 #define ESR_ELx_FSC_PERM	(0x0C)
+#define ESR_ELx_FSC_SEA_TTW0	(0x14)
+#define ESR_ELx_FSC_SEA_TTW1	(0x15)
+#define ESR_ELx_FSC_SEA_TTW2	(0x16)
+#define ESR_ELx_FSC_SEA_TTW3	(0x17)
+#define ESR_ELx_FSC_SECC	(0x18)
+#define ESR_ELx_FSC_SECC_TTW0	(0x1c)
+#define ESR_ELx_FSC_SECC_TTW1	(0x1d)
+#define ESR_ELx_FSC_SECC_TTW2	(0x1e)
+#define ESR_ELx_FSC_SECC_TTW3	(0x1f)
 
 /* ISS field definitions for Data Aborts */
 #define ESR_ELx_ISV_SHIFT	(24)
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 0df3fc3a0173..26b0c97df986 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -319,21 +319,6 @@
 				 BIT(18) |		\
 				 GENMASK(16, 15))
 
-/* For compatibility with fault code shared with 32-bit */
-#define FSC_FAULT	ESR_ELx_FSC_FAULT
-#define FSC_ACCESS	ESR_ELx_FSC_ACCESS
-#define FSC_PERM	ESR_ELx_FSC_PERM
-#define FSC_SEA		ESR_ELx_FSC_EXTABT
-#define FSC_SEA_TTW0	(0x14)
-#define FSC_SEA_TTW1	(0x15)
-#define FSC_SEA_TTW2	(0x16)
-#define FSC_SEA_TTW3	(0x17)
-#define FSC_SECC	(0x18)
-#define FSC_SECC_TTW0	(0x1c)
-#define FSC_SECC_TTW1	(0x1d)
-#define FSC_SECC_TTW2	(0x1e)
-#define FSC_SECC_TTW3	(0x1f)
-
 /* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */
 #define HPFAR_MASK	(~UL(0xf))
 /*
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 9bdba47f7e14..193583df2d9c 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -349,16 +349,16 @@ static __always_inline u8 kvm_vcpu_trap_get_fault_level(const struct kvm_vcpu *v
 static __always_inline bool kvm_vcpu_abt_issea(const struct kvm_vcpu *vcpu)
 {
 	switch (kvm_vcpu_trap_get_fault(vcpu)) {
-	case FSC_SEA:
-	case FSC_SEA_TTW0:
-	case FSC_SEA_TTW1:
-	case FSC_SEA_TTW2:
-	case FSC_SEA_TTW3:
-	case FSC_SECC:
-	case FSC_SECC_TTW0:
-	case FSC_SECC_TTW1:
-	case FSC_SECC_TTW2:
-	case FSC_SECC_TTW3:
+	case ESR_ELx_FSC_EXTABT:
+	case ESR_ELx_FSC_SEA_TTW0:
+	case ESR_ELx_FSC_SEA_TTW1:
+	case ESR_ELx_FSC_SEA_TTW2:
+	case ESR_ELx_FSC_SEA_TTW3:
+	case ESR_ELx_FSC_SECC:
+	case ESR_ELx_FSC_SECC_TTW0:
+	case ESR_ELx_FSC_SECC_TTW1:
+	case ESR_ELx_FSC_SECC_TTW2:
+	case ESR_ELx_FSC_SECC_TTW3:
 		return true;
 	default:
 		return false;
@@ -373,8 +373,26 @@ static __always_inline int kvm_vcpu_sys_get_rt(struct kvm_vcpu *vcpu)
 
 static inline bool kvm_is_write_fault(struct kvm_vcpu *vcpu)
 {
-	if (kvm_vcpu_abt_iss1tw(vcpu))
-		return true;
+	if (kvm_vcpu_abt_iss1tw(vcpu)) {
+		/*
+		 * Only a permission fault on a S1PTW should be
+		 * considered as a write. Otherwise, page tables baked
+		 * in a read-only memslot will result in an exception
+		 * being delivered in the guest.
+		 *
+		 * The drawback is that we end-up faulting twice if the
+		 * guest is using any of HW AF/DB: a translation fault
+		 * to map the page containing the PT (read only at
+		 * first), then a permission fault to allow the flags
+		 * to be set.
+		 */
+		switch (kvm_vcpu_trap_get_fault_type(vcpu)) {
+		case ESR_ELx_FSC_PERM:
+			return true;
+		default:
+			return false;
+		}
+	}
 
 	if (kvm_vcpu_trap_is_iabt(vcpu))
 		return false;