[Xen-devel] [RFC 1/6] xen/arm: Re-enable interrupt later in the trap path

[Andrii Anisov <andrii.anisov@gmail.com>]

From: Julien Grall <julien.grall@arm.com>

This makes function enter_hypervisor_head() being executed with
irqs locked.

Signed-off-by: Julien Grall <julien.grall@arm.com>
[Andrii: add a justification commit message]
Signed-off-by: Andrii Anisov <andrii_anisov@epam.com>
---
 xen/arch/arm/arm64/entry.S | 11 +++++------
 xen/arch/arm/traps.c       |  6 ++++++
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/arm64/entry.S b/xen/arch/arm/arm64/entry.S
index 97b05f5..8f28789 100644
--- a/xen/arch/arm/arm64/entry.S
+++ b/xen/arch/arm/arm64/entry.S
@@ -195,7 +195,6 @@ hyp_error_invalid:
 
 hyp_error:
         entry   hyp=1
-        msr     daifclr, #2
         mov     x0, sp
         bl      do_trap_hyp_serror
         exit    hyp=1
@@ -203,7 +202,7 @@ hyp_error:
 /* Traps taken in Current EL with SP_ELx */
 hyp_sync:
         entry   hyp=1
-        msr     daifclr, #6
+        msr     daifclr, #4
         mov     x0, sp
         bl      do_trap_hyp_sync
         exit    hyp=1
@@ -304,7 +303,7 @@ guest_sync_slowpath:
         ALTERNATIVE("bl check_pending_vserror; cbnz x0, 1f",
                     "nop; nop",
                     SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT)
-        msr     daifclr, #6
+        msr     daifclr, #4
         mov     x0, sp
         bl      do_trap_guest_sync
 1:
@@ -332,7 +331,7 @@ guest_fiq_invalid:
 
 guest_error:
         entry   hyp=0, compat=0
-        msr     daifclr, #6
+        msr     daifclr, #4
         mov     x0, sp
         bl      do_trap_guest_serror
         exit    hyp=0, compat=0
@@ -347,7 +346,7 @@ guest_sync_compat:
         ALTERNATIVE("bl check_pending_vserror; cbnz x0, 1f",
                     "nop; nop",
                     SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT)
-        msr     daifclr, #6
+        msr     daifclr, #4
         mov     x0, sp
         bl      do_trap_guest_sync
 1:
@@ -375,7 +374,7 @@ guest_fiq_invalid_compat:
 
 guest_error_compat:
         entry   hyp=0, compat=1
-        msr     daifclr, #6
+        msr     daifclr, #4
         mov     x0, sp
         bl      do_trap_guest_serror
         exit    hyp=0, compat=1
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 3103620..5a9dc66 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2017,6 +2017,8 @@ static void enter_hypervisor_head(struct cpu_user_regs *regs)
     {
         struct vcpu *v = current;
 
+        ASSERT(!local_irq_is_enabled());
+
         /* If the guest has disabled the workaround, bring it back on. */
         if ( needs_ssbd_flip(v) )
             arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_2_FID, 1, NULL);
@@ -2051,6 +2053,7 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
     const union hsr hsr = { .bits = regs->hsr };
 
     enter_hypervisor_head(regs);
+    local_irq_enable();
 
     switch ( hsr.ec )
     {
@@ -2186,6 +2189,7 @@ void do_trap_hyp_sync(struct cpu_user_regs *regs)
     const union hsr hsr = { .bits = regs->hsr };
 
     enter_hypervisor_head(regs);
+    local_irq_enable();
 
     switch ( hsr.ec )
     {
@@ -2224,6 +2228,7 @@ void do_trap_hyp_sync(struct cpu_user_regs *regs)
 void do_trap_hyp_serror(struct cpu_user_regs *regs)
 {
     enter_hypervisor_head(regs);
+    local_irq_enable();
 
     __do_trap_serror(regs, VABORT_GEN_BY_GUEST(regs));
 }
@@ -2231,6 +2236,7 @@ void do_trap_hyp_serror(struct cpu_user_regs *regs)
 void do_trap_guest_serror(struct cpu_user_regs *regs)
 {
     enter_hypervisor_head(regs);
+    local_irq_enable();
 
     __do_trap_serror(regs, true);
 }
-- 
2.7.4


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