[Xen-devel] [PATCH for-4.12 v4 2/4] xen/arm: vsysreg: Add wrapper to handle sysreg access trapped by HCR_EL2.TVM

[Julien Grall <julien.grall@xxxxxxx>]

A follow-up patch will require to emulate some accesses to system
registers trapped by HCR_EL2.TVM. When set, all NS EL1 writes to the
virtual memory control registers will be trapped to the hypervisor.

This patch adds the infrastructure to passthrough the access to the host
registers.

Note that HCR_EL2.TVM will be set in a follow-up patch dynamically.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

---
    Changes in v4:
        - Add Stefano's reviewed by

    Changes in v2:
        - Add missing include vreg.h
        - Update documentation reference to the lastest one
---
 xen/arch/arm/arm64/vsysreg.c | 58 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/xen/arch/arm/arm64/vsysreg.c b/xen/arch/arm/arm64/vsysreg.c
index 6e60824572..16ac9c344a 100644
--- a/xen/arch/arm/arm64/vsysreg.c
+++ b/xen/arch/arm/arm64/vsysreg.c
@@ -21,8 +21,49 @@
 #include <asm/current.h>
 #include <asm/regs.h>
 #include <asm/traps.h>
+#include <asm/vreg.h>
 #include <asm/vtimer.h>
 
+/*
+ * Macro to help generating helpers for registers trapped when
+ * HCR_EL2.TVM is set.
+ *
+ * Note that it only traps NS write access from EL1.
+ */
+#define TVM_REG(reg)                                                \
+static bool vreg_emulate_##reg(struct cpu_user_regs *regs,          \
+                               uint64_t *r, bool read)              \
+{                                                                   \
+    GUEST_BUG_ON(read);                                             \
+    WRITE_SYSREG64(*r, reg);                                        \
+                                                                    \
+    return true;                                                    \
+}
+
+/* Defining helpers for emulating sysreg registers. */
+TVM_REG(SCTLR_EL1)
+TVM_REG(TTBR0_EL1)
+TVM_REG(TTBR1_EL1)
+TVM_REG(TCR_EL1)
+TVM_REG(ESR_EL1)
+TVM_REG(FAR_EL1)
+TVM_REG(AFSR0_EL1)
+TVM_REG(AFSR1_EL1)
+TVM_REG(MAIR_EL1)
+TVM_REG(AMAIR_EL1)
+TVM_REG(CONTEXTIDR_EL1)
+
+/* Macro to generate easily case for co-processor emulation */
+#define GENERATE_CASE(reg)                                              \
+    case HSR_SYSREG_##reg:                                              \
+    {                                                                   \
+        bool res;                                                       \
+                                                                        \
+        res = vreg_emulate_sysreg64(regs, hsr, vreg_emulate_##reg);     \
+        ASSERT(res);                                                    \
+        break;                                                          \
+    }
+
 void do_sysreg(struct cpu_user_regs *regs,
                const union hsr hsr)
 {
@@ -44,6 +85,23 @@ void do_sysreg(struct cpu_user_regs *regs,
         break;
 
     /*
+     * HCR_EL2.TVM
+     *
+     * ARMv8 (DDI 0487D.a): Table D1-38
+     */
+    GENERATE_CASE(SCTLR_EL1)
+    GENERATE_CASE(TTBR0_EL1)
+    GENERATE_CASE(TTBR1_EL1)
+    GENERATE_CASE(TCR_EL1)
+    GENERATE_CASE(ESR_EL1)
+    GENERATE_CASE(FAR_EL1)
+    GENERATE_CASE(AFSR0_EL1)
+    GENERATE_CASE(AFSR1_EL1)
+    GENERATE_CASE(MAIR_EL1)
+    GENERATE_CASE(AMAIR_EL1)
+    GENERATE_CASE(CONTEXTIDR_EL1)
+
+    /*
      * MDCR_EL2.TDRA
      *
      * ARMv8 (DDI 0487A.d): D1-1508 Table D1-57
-- 
2.11.0


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