[PATCH v3 16/20] KVM: arm64: Save/Restore guest DISR_EL1

[james.morse@arm.com (James Morse)]

If we deliver a virtual SError to the guest, the guest may defer it
with an ESB instruction. The guest reads the deferred value via DISR_EL1,
but the guests view of DISR_EL1 is re-mapped to VDISR_EL2 when HCR_EL2.AMO
is set.

Add the KVM code to save/restore VDISR_EL2, and make it accessible to
userspace as DISR_EL1.

Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/arm64/include/asm/kvm_host.h | 1 +
 arch/arm64/include/asm/sysreg.h   | 1 +
 arch/arm64/kvm/hyp/sysreg-sr.c    | 6 ++++++
 arch/arm64/kvm/sys_regs.c         | 1 +
 4 files changed, 9 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 0af35e71fedb..9564e6d56b79 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -120,6 +120,7 @@ enum vcpu_sysreg {
 	PAR_EL1,	/* Physical Address Register */
 	MDSCR_EL1,	/* Monitor Debug System Control Register */
 	MDCCINT_EL1,	/* Monitor Debug Comms Channel Interrupt Enable Reg */
+	DISR_EL1,	/* Deferred Interrupt Status Register */
 
 	/* Performance Monitors Registers */
 	PMCR_EL0,	/* Control Register */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index a493e93de296..1b8b9012234d 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -256,6 +256,7 @@
 #define SYS_VSESR_EL2			sys_reg(3, 4, 5, 2, 3)
 #define SYS_FPEXC32_EL2			sys_reg(3, 4, 5, 3, 0)
 
+#define SYS_VDISR_EL2			sys_reg(3, 4, 12, 1,  1)
 #define __SYS__AP0Rx_EL2(x)		sys_reg(3, 4, 12, 8, x)
 #define SYS_ICH_AP0R0_EL2		__SYS__AP0Rx_EL2(0)
 #define SYS_ICH_AP0R1_EL2		__SYS__AP0Rx_EL2(1)
diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
index 934137647837..f4d604803b29 100644
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -66,6 +66,9 @@ static void __hyp_text __sysreg_save_state(struct kvm_cpu_context *ctxt)
 	ctxt->gp_regs.sp_el1		= read_sysreg(sp_el1);
 	ctxt->gp_regs.elr_el1		= read_sysreg_el1(elr);
 	ctxt->gp_regs.spsr[KVM_SPSR_EL1]= read_sysreg_el1(spsr);
+
+	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN))
+		ctxt->sys_regs[DISR_EL1] = read_sysreg_s(SYS_VDISR_EL2);
 }
 
 static hyp_alternate_select(__sysreg_call_save_host_state,
@@ -119,6 +122,9 @@ static void __hyp_text __sysreg_restore_state(struct kvm_cpu_context *ctxt)
 	write_sysreg(ctxt->gp_regs.sp_el1,		sp_el1);
 	write_sysreg_el1(ctxt->gp_regs.elr_el1,		elr);
 	write_sysreg_el1(ctxt->gp_regs.spsr[KVM_SPSR_EL1],spsr);
+
+	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN))
+		write_sysreg_s(ctxt->sys_regs[DISR_EL1], SYS_VDISR_EL2);
 }
 
 static hyp_alternate_select(__sysreg_call_restore_host_state,
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 2e070d3baf9f..713275b501ce 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -963,6 +963,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_AMAIR_EL1), access_vm_reg, reset_amair_el1, AMAIR_EL1 },
 
 	{ SYS_DESC(SYS_VBAR_EL1), NULL, reset_val, VBAR_EL1, 0 },
+	{ SYS_DESC(SYS_DISR_EL1), NULL, reset_val, DISR_EL1, 0 },
 
 	{ SYS_DESC(SYS_ICC_IAR0_EL1), write_to_read_only },
 	{ SYS_DESC(SYS_ICC_EOIR0_EL1), read_from_write_only },
-- 
2.13.3