[PATCH 3/3] KVM: arm64: Handle SCXTNUM_ELx traps

[Marc Zyngier <maz@kernel.org>]

As the kernel never sets HCR_EL2.EnSCXT, accesses to SCXTNUM_ELx
will trap to EL2. Let's handle that as gracefully as possible
by injecting an UNDEF exception into the guest. This is consistent
with the guest's view of ID_AA64PFR0_EL1.CSV2 being at most 1.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201110141308.451654-4-maz@kernel.org
---
 arch/arm64/include/asm/sysreg.h | 4 ++++
 arch/arm64/kvm/sys_regs.c       | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index d52c1b3ce589..a427a5653369 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -372,6 +372,8 @@
 #define SYS_CONTEXTIDR_EL1		sys_reg(3, 0, 13, 0, 1)
 #define SYS_TPIDR_EL1			sys_reg(3, 0, 13, 0, 4)
 
+#define SYS_SCXTNUM_EL1			sys_reg(3, 0, 13, 0, 7)
+
 #define SYS_CNTKCTL_EL1			sys_reg(3, 0, 14, 1, 0)
 
 #define SYS_CCSIDR_EL1			sys_reg(3, 1, 0, 0, 0)
@@ -404,6 +406,8 @@
 #define SYS_TPIDR_EL0			sys_reg(3, 3, 13, 0, 2)
 #define SYS_TPIDRRO_EL0			sys_reg(3, 3, 13, 0, 3)
 
+#define SYS_SCXTNUM_EL0			sys_reg(3, 3, 13, 0, 7)
+
 /* Definitions for system register interface to AMU for ARMv8.4 onwards */
 #define SYS_AM_EL0(crm, op2)		sys_reg(3, 3, 13, (crm), (op2))
 #define SYS_AMCR_EL0			SYS_AM_EL0(2, 0)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index b0022f37c8f1..c1726fb7f3d9 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1598,6 +1598,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_CONTEXTIDR_EL1), access_vm_reg, reset_val, CONTEXTIDR_EL1, 0 },
 	{ SYS_DESC(SYS_TPIDR_EL1), NULL, reset_unknown, TPIDR_EL1 },
 
+	{ SYS_DESC(SYS_SCXTNUM_EL1), undef_access },
+
 	{ SYS_DESC(SYS_CNTKCTL_EL1), NULL, reset_val, CNTKCTL_EL1, 0},
 
 	{ SYS_DESC(SYS_CCSIDR_EL1), access_ccsidr },
@@ -1626,6 +1628,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_TPIDR_EL0), NULL, reset_unknown, TPIDR_EL0 },
 	{ SYS_DESC(SYS_TPIDRRO_EL0), NULL, reset_unknown, TPIDRRO_EL0 },
 
+	{ SYS_DESC(SYS_SCXTNUM_EL0), undef_access },
+
 	{ SYS_DESC(SYS_AMCR_EL0), undef_access },
 	{ SYS_DESC(SYS_AMCFGR_EL0), undef_access },
 	{ SYS_DESC(SYS_AMCGCR_EL0), undef_access },
-- 
2.28.0

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