arm/arm64: KVM: add guest SEA support

Currently external aborts are unsupported by the guest abort
handling. Add handling for SEAs so that the host kernel reports
SEAs which occur in the guest kernel.

When an SEA occurs in the guest kernel, the guest exits and is
routed to kvm_handle_guest_abort(). Prior to this patch, a print
message of an unsupported FSC would be printed and nothing else
would happen. With this patch, the code gets routed to the APEI
handling of SEAs in the host kernel to report the SEA information.
Signed-off-by: Tyler Baicar <tbaicar@codeaurora.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm/include/asm/kvm_arm.h

@@ -187,6 +187,16 @@
 #define FSC_FAULT	(0x04)
 #define FSC_ACCESS	(0x08)
 #define FSC_PERM	(0x0c)
+#define FSC_SEA		(0x10)
+#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	(~0xf)

arch/arm/include/asm/system_misc.h

@@ -22,6 +22,11 @@ extern void (*arm_pm_idle)(void);
 
 extern unsigned int user_debug;
 
+static inline int handle_guest_sea(phys_addr_t addr, unsigned int esr)
+{
+	return -1;
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_ARM_SYSTEM_MISC_H */

arch/arm64/include/asm/kvm_arm.h

@@ -204,6 +204,16 @@
 #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))

arch/arm64/include/asm/system_misc.h

@@ -56,6 +56,8 @@ extern void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
 	__show_ratelimited;						\
 })
 
+int handle_guest_sea(phys_addr_t addr, unsigned int esr);
+
 #endif	/* __ASSEMBLY__ */
 
 #endif	/* __ASM_SYSTEM_MISC_H */

arch/arm64/mm/fault.c

@@ -532,6 +532,7 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
 {
 	struct siginfo info;
 	const struct fault_info *inf;
+	int ret = 0;
 
 	inf = esr_to_fault_info(esr);
 	pr_err("Synchronous External Abort: %s (0x%08x) at 0x%016lx\n",
@@ -546,7 +547,7 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
 		if (interrupts_enabled(regs))
 			nmi_enter();
 
-		ghes_notify_sea();
+		ret = ghes_notify_sea();
 
 		if (interrupts_enabled(regs))
 			nmi_exit();
@@ -561,7 +562,7 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
 		info.si_addr  = (void __user *)addr;
 	arm64_notify_die("", regs, &info, esr);
 
-	return 0;
+	return ret;
 }
 
 static const struct fault_info fault_info[] = {
@@ -631,6 +632,23 @@ static const struct fault_info fault_info[] = {
 	{ do_bad,		SIGBUS,  0,		"unknown 63"			},
 };
 
+/*
+ * Handle Synchronous External Aborts that occur in a guest kernel.
+ *
+ * The return value will be zero if the SEA was successfully handled
+ * and non-zero if there was an error processing the error or there was
+ * no error to process.
+ */
+int handle_guest_sea(phys_addr_t addr, unsigned int esr)
+{
+	int ret = -ENOENT;
+
+	if (IS_ENABLED(CONFIG_ACPI_APEI_SEA))
+		ret = ghes_notify_sea();
+
+	return ret;
+}
+
 /*
  * Dispatch a data abort to the relevant handler.
  */

drivers/acpi/apei/ghes.c

@@ -816,17 +816,22 @@ static struct notifier_block ghes_notifier_sci = {
 #ifdef CONFIG_ACPI_APEI_SEA
 static LIST_HEAD(ghes_sea);
 
-void ghes_notify_sea(void)
+/*
+ * Return 0 only if one of the SEA error sources successfully reported an error
+ * record sent from the firmware.
+ */
+int ghes_notify_sea(void)
 {
 	struct ghes *ghes;
+	int ret = -ENOENT;
 
-	/*
-	 * synchronize_rcu() will wait for nmi_exit(), so no need to
-	 * rcu_read_lock().
-	 */
+	rcu_read_lock();
 	list_for_each_entry_rcu(ghes, &ghes_sea, list) {
-		ghes_proc(ghes);
+		if (!ghes_proc(ghes))
+			ret = 0;
 	}
+	rcu_read_unlock();
+	return ret;
 }
 
 static void ghes_sea_add(struct ghes *ghes)

include/acpi/ghes.h

@@ -113,6 +113,6 @@ static inline void *acpi_hest_get_next(struct acpi_hest_generic_data *gdata)
 	return (void *)(gdata) + acpi_hest_get_record_size(gdata);
 }
 
-void ghes_notify_sea(void);
+int ghes_notify_sea(void);
 
 #endif /* GHES_H */

virt/kvm/arm/mmu.c

@@ -29,6 +29,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_emulate.h>
 #include <asm/virt.h>
+#include <asm/system_misc.h>
 
 #include "trace.h"
 
@@ -1427,6 +1428,25 @@ static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
 		kvm_set_pfn_accessed(pfn);
 }
 
+static bool is_abort_sea(unsigned long fault_status)
+{
+	switch (fault_status) {
+	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:
+		return true;
+	default:
+		return false;
+	}
+}
+
 /**
  * kvm_handle_guest_abort - handles all 2nd stage aborts
  * @vcpu:	the VCPU pointer
@@ -1449,19 +1469,29 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	gfn_t gfn;
 	int ret, idx;
 
+	fault_status = kvm_vcpu_trap_get_fault_type(vcpu);
+
+	fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
+
+	/*
+	 * The host kernel will handle the synchronous external abort. There
+	 * is no need to pass the error into the guest.
+	 */
+	if (is_abort_sea(fault_status)) {
+		if (!handle_guest_sea(fault_ipa, kvm_vcpu_get_hsr(vcpu)))
+			return 1;
+	}
+
 	is_iabt = kvm_vcpu_trap_is_iabt(vcpu);
 	if (unlikely(!is_iabt && kvm_vcpu_dabt_isextabt(vcpu))) {
 		kvm_inject_vabt(vcpu);
 		return 1;
 	}
 
-	fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
-
 	trace_kvm_guest_fault(*vcpu_pc(vcpu), kvm_vcpu_get_hsr(vcpu),
 			      kvm_vcpu_get_hfar(vcpu), fault_ipa);
 
 	/* Check the stage-2 fault is trans. fault or write fault */
-	fault_status = kvm_vcpu_trap_get_fault_type(vcpu);
 	if (fault_status != FSC_FAULT && fault_status != FSC_PERM &&
 	    fault_status != FSC_ACCESS) {
 		kvm_err("Unsupported FSC: EC=%#x xFSC=%#lx ESR_EL2=%#lx\n",