xen/arm: do_trap_hypervisor: Separate hypervisor and guest traps

The function do_trap_hypervisor is currently handling both trap coming
from the hypervisor and the guest. This makes difficult to get specific
behavior when a trap is coming from either the guest or the hypervisor.

Split the function into two parts:
    - do_trap_guest_sync to handle guest traps
    - do_trap_hyp_sync to handle hypervisor traps

On AArch32, the Hyp Trap Exception provides the standard mechanism for
trapping Guest OS functions to the hypervisor (see B1.14.1 in ARM DDI
0406C.c). It cannot be generated when generated when the processor is in
Hyp Mode, instead other exception will be used. So it is fine to replace
the call to do_trap_hypervisor by do_trap_guest_sync.

For AArch64, there are two distincts exception depending whether the
exception was taken from the current level (hypervisor) or lower level
(guest).

Note that the unknown traps from guests will lead to panic Xen. This is
already behavior and is left unchanged for simplicy. A follow-up patch
will address that.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

diff --git a/xen/arch/arm/arm32/entry.S b/xen/arch/arm/arm32/entry.S
index 05733089f746a9aa758fc6c6d4e25f8978cb2560..120922e64e15b7c69f6e4fd0e83440d7653635b9 100644 (file)
--- a/xen/arch/arm/arm32/entry.S
+++ b/xen/arch/arm/arm32/entry.S
@@ -152,14 +152,14 @@ GLOBAL(hyp_traps_vector)
         b trap_hypervisor_call          /* 0x08 - Hypervisor Call */
         b trap_prefetch_abort           /* 0x0c - Prefetch Abort */
         b trap_data_abort               /* 0x10 - Data Abort */
-        b trap_hypervisor               /* 0x14 - Hypervisor */
+        b trap_guest_sync               /* 0x14 - Hypervisor */
         b trap_irq                      /* 0x18 - IRQ */
         b trap_fiq                      /* 0x1c - FIQ */
 
 DEFINE_TRAP_ENTRY(undefined_instruction)
 DEFINE_TRAP_ENTRY(hypervisor_call)
 DEFINE_TRAP_ENTRY(prefetch_abort)
-DEFINE_TRAP_ENTRY(hypervisor)
+DEFINE_TRAP_ENTRY(guest_sync)
 DEFINE_TRAP_ENTRY_NOIRQ(irq)
 DEFINE_TRAP_ENTRY_NOIRQ(fiq)
 DEFINE_TRAP_ENTRY_NOABORT(data_abort)

diff --git a/xen/arch/arm/arm64/entry.S b/xen/arch/arm/arm64/entry.S
index 137e67c674b09a5de45d213198597a2f1b82959f..06afc8a4e4b86111be40deebb03646266268114c 100644 (file)
--- a/xen/arch/arm/arm64/entry.S
+++ b/xen/arch/arm/arm64/entry.S
@@ -189,7 +189,7 @@ hyp_sync:
         entry   hyp=1
         msr     daifclr, #6
         mov     x0, sp
-        bl      do_trap_hypervisor
+        bl      do_trap_hyp_sync
         exit    hyp=1
 
 hyp_irq:
@@ -211,7 +211,7 @@ guest_sync:
                     SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT)
         msr     daifclr, #6
         mov     x0, sp
-        bl      do_trap_hypervisor
+        bl      do_trap_guest_sync
 1:
         exit    hyp=0, compat=0
 
@@ -254,7 +254,7 @@ guest_sync_compat:
                     SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT)
         msr     daifclr, #6
         mov     x0, sp
-        bl      do_trap_hypervisor
+        bl      do_trap_guest_sync
 1:
         exit    hyp=0, compat=1
 

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 6010c96c5469868f802fa26028f36d93201cc12e..645812210d55f0735be2ce80aeef272bfa876d26 100644 (file)
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2805,7 +2805,7 @@ static void enter_hypervisor_head(struct cpu_user_regs *regs)
     }
 }
 
-asmlinkage void do_trap_hypervisor(struct cpu_user_regs *regs)
+asmlinkage void do_trap_guest_sync(struct cpu_user_regs *regs)
 {
     const union hsr hsr = { .bits = regs->hsr };
 
@@ -2925,6 +2925,21 @@ asmlinkage void do_trap_hypervisor(struct cpu_user_regs *regs)
         do_trap_data_abort_guest(regs, hsr);
         break;
 
+    default:
+        printk("Unknown Guest Trap. HSR=0x%x EC=0x%x IL=%x Syndrome=0x%"PRIx32"\n",
+               hsr.bits, hsr.ec, hsr.len, hsr.iss);
+        do_unexpected_trap("Guest", regs);
+    }
+}
+
+asmlinkage void do_trap_hyp_sync(struct cpu_user_regs *regs)
+{
+    const union hsr hsr = { .bits = regs->hsr };
+
+    enter_hypervisor_head(regs);
+
+    switch ( hsr.ec )
+    {
 #ifdef CONFIG_ARM_64
     case HSR_EC_BRK:
         do_trap_brk(regs, hsr);