[Xen-devel] [PATCH v1 03/15] arm: Placeholder for handling Group0/1 traps for Cavium Erratum 30115

[Manish Jaggi <manish.jaggi@xxxxxxxxxx>]

Since this is a SoC errata and trapping of certain group1 registers
should not affect the normal flow. A new file vgic-v3-sr.c is added.

Function vgic_v3_handle_cpuif_access is called from do_trap_guest_sync
if ARM64_WORKAROUND_CAVIUM_30115 capability is found.

A flag skip_hyp_tail is introduced in struct cpu_info. This flag
specifies
that leave_hypervisor_tail not to be called when handling group1 traps
under this errata. enter_hypervisor_head is not invoked when workaround
30115 is in place. enter_hypervisor_head and leave_hypervisor_tail are
invoked in sync, if one is not called other one should be skipped,
otherwise guest vGIC state be out-of-date.

Signed-off-by: Manish Jaggi <manish.jaggi@xxxxxxxxxx>

diff --git a/xen/arch/arm/arm64/Makefile b/xen/arch/arm/arm64/Makefile
index 718fe44455..02cc115239 100644
--- a/xen/arch/arm/arm64/Makefile
+++ b/xen/arch/arm/arm64/Makefile
@@ -11,3 +11,4 @@ obj-y += smpboot.o
 obj-y += traps.o
 obj-y += vfp.o
 obj-y += vsysreg.o
+obj-$(CONFIG_CAVIUM_ERRATUM_30115) += vgic-v3-sr.o
diff --git a/xen/arch/arm/arm64/vgic-v3-sr.c b/xen/arch/arm/arm64/vgic-v3-sr.c
new file mode 100644
index 0000000000..56b02fd45b
--- /dev/null
+++ b/xen/arch/arm/arm64/vgic-v3-sr.c
@@ -0,0 +1,56 @@
+/*
+ * xen/arch/arm/arm64/vgic-v3-sr.c
+ *
+ * Code to handle Cavium Erratum 30115
+ *
+ * Manish Jaggi <manish.jaggi@xxxxxxxxxx>
+ * Copyright (c) 2018 Cavium.
+ *
+ * Ths program is free software; you can redistribute it and/or
+ * modify it under the terms and conditions of the GNU General Public
+ * License, version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <asm/current.h>
+#include <asm/regs.h>
+#include <asm/traps.h>
+#include <asm/system.h>
+
+bool vgic_v3_handle_cpuif_access(struct cpu_user_regs *regs, const union hsr 
hsr)
+{
+    bool ret = true;
+
+    /* Disabling interrupts to prevent change in guest state */
+    local_irq_disable();
+    if ( hsr.ec != HSR_EC_SYSREG )
+    {
+        ret = false;
+        goto end;
+    }
+
+    switch ( hsr.bits & HSR_SYSREG_REGS_MASK )
+    {
+    default:
+        ret = false;
+        break;
+    }
+end:
+    local_irq_enable();
+
+    return ret;
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
+
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index f6f6de3691..25778018fb 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2103,6 +2103,27 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
 {
     const union hsr hsr = { .bits = regs->hsr };
 
+    if ( check_workaround_30115() )
+    {
+        bool ret;
+        ret  = vgic_v3_handle_cpuif_access(regs, hsr);
+        if ( ret )
+        {
+           /* if true, g0/g1 vgic register trap is emulated for errata
+            * so rest of handling of do_trap_guest_sync is not required.
+            */
+            advance_pc(regs, hsr);
+            /*
+             * enter_hypervisor_head is not invoked when workaround 30115
+             * is in place. enter_hypervisor_head and leave_hypervisor_tail
+             * are invoked in sync, if one is not called other one should be
+             * skipped, otherwise guest vGIC state be out-of-date.
+             */
+            get_cpu_info()->skip_hyp_tail = true;
+            return;
+        }
+    }
+
     enter_hypervisor_head(regs);
 
     switch (hsr.ec) {
@@ -2295,6 +2316,16 @@ void do_trap_fiq(struct cpu_user_regs *regs)
 
 void leave_hypervisor_tail(void)
 {
+    /*
+     * if skip_hyp_tail is set simply retrun;
+     */
+    if ( unlikely(get_cpu_info()->skip_hyp_tail) )
+    {
+        /* clear it */
+        get_cpu_info()->skip_hyp_tail = false;
+        return;
+    }
+
     while (1)
     {
         local_irq_disable();
diff --git a/xen/include/asm-arm/arm64/traps.h 
b/xen/include/asm-arm/arm64/traps.h
index 2379b578cb..45fe582abd 100644
--- a/xen/include/asm-arm/arm64/traps.h
+++ b/xen/include/asm-arm/arm64/traps.h
@@ -3,6 +3,9 @@
 
 void inject_undef64_exception(struct cpu_user_regs *regs, int instr_len);
 
+bool vgic_v3_handle_cpuif_access(struct cpu_user_regs *regs,
+                                const union hsr hsr);
+
 void do_sysreg(struct cpu_user_regs *regs,
                const union hsr hsr);
 
diff --git a/xen/include/asm-arm/current.h b/xen/include/asm-arm/current.h
index 7a0971fdea..d7b3f4ddb4 100644
--- a/xen/include/asm-arm/current.h
+++ b/xen/include/asm-arm/current.h
@@ -21,7 +21,8 @@ DECLARE_PER_CPU(struct vcpu *, curr_vcpu);
 struct cpu_info {
     struct cpu_user_regs guest_cpu_user_regs;
     unsigned long elr;
-    unsigned int pad;
+    unsigned int pad:31;
+    bool skip_hyp_tail:1;
 };
 
 static inline struct cpu_info *get_cpu_info(void)
-- 
2.14.1


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