system/xen: XSA 199-201 update.

Signed-off-by: Mario Preksavec <mario@slackware.hr>

11 files changed, 613 insertions, 6 deletions

diff --git a/system/xen/dom0/config-4.4.29-xen.i486 b/system/xen/dom0/config-4.4.38-xen.i686
index 3af4f7cd41..cfbfe0d202 100644
--- a/system/xen/dom0/config-4.4.29-xen.i486
+++ b/system/xen/dom0/config-4.4.38-xen.i686
@@ -1,6 +1,6 @@
 #
 # Automatically generated file; DO NOT EDIT.
-# Linux/x86 4.4.29 Kernel Configuration
+# Linux/x86 4.4.38 Kernel Configuration
 #
 # CONFIG_64BIT is not set
 CONFIG_X86_32=y
diff --git a/system/xen/dom0/config-4.4.29-xen.x86_64 b/system/xen/dom0/config-4.4.38-xen.x86_64
index 7b4e532ab2..db5c9e8c51 100644
--- a/system/xen/dom0/config-4.4.29-xen.x86_64
+++ b/system/xen/dom0/config-4.4.38-xen.x86_64
@@ -1,6 +1,6 @@
 #
 # Automatically generated file; DO NOT EDIT.
-# Linux/x86 4.4.29 Kernel Configuration
+# Linux/x86 4.4.38 Kernel Configuration
 #
 CONFIG_64BIT=y
 CONFIG_X86_64=y
diff --git a/system/xen/dom0/kernel-xen.sh b/system/xen/dom0/kernel-xen.sh
index b84513786e..07d1a1f8b1 100644
--- a/system/xen/dom0/kernel-xen.sh
+++ b/system/xen/dom0/kernel-xen.sh
@@ -5,7 +5,7 @@
 # Written by Chris Abela <chris.abela@maltats.com>, 20100515
 # Modified by Mario Preksavec <mario@slackware.hr>
 
-KERNEL=${KERNEL:-4.4.29}
+KERNEL=${KERNEL:-4.4.38}
 XEN=${XEN:-4.7.1}
 BOOTLOADER=${BOOTLOADER:-lilo}
 
@@ -15,7 +15,7 @@ ROOTDEV=${ROOTDEV:-/dev/sda2}
 
 if [ -z "$ARCH" ]; then
   case "$( uname -m )" in
-      i?86) ARCH=i486 ;;
+      i?86) ARCH=i686 ;;
     x86_64) ARCH=x86_64 ;;
          *) echo "Unsupported architecture detected ($ARCH)"; exit ;;
   esac
diff --git a/system/xen/domU/domU.sh b/system/xen/domU/domU.sh
index 1cd3e0d92c..6d61485b32 100644
--- a/system/xen/domU/domU.sh
+++ b/system/xen/domU/domU.sh
@@ -7,7 +7,7 @@
 
 set -e
 
-KERNEL=${KERNEL:-4.4.29}
+KERNEL=${KERNEL:-4.4.38}
 
 # Build an image for the root file system and another for the swap
 # Default values : 8GB and 500MB resepectively.
diff --git a/system/xen/xen.SlackBuild b/system/xen/xen.SlackBuild
index 088d87b259..e4eabedb97 100644
--- a/system/xen/xen.SlackBuild
+++ b/system/xen/xen.SlackBuild
@@ -24,7 +24,7 @@
 
 PRGNAM=xen
 VERSION=${VERSION:-4.7.1}
-BUILD=${BUILD:-2}
+BUILD=${BUILD:-3}
 TAG=${TAG:-_SBo}
 
 SEABIOS=${SEABIOS:-1.9.2}
diff --git a/system/xen/xsa/xsa199-qemut.patch b/system/xen/xsa/xsa199-qemut.patch
new file mode 100644
index 0000000000..50a7eb6c92
--- /dev/null
+++ b/system/xen/xsa/xsa199-qemut.patch
@@ -0,0 +1,89 @@
+From b73bd1edc05d1bad5c018228146930d79315a5da Mon Sep 17 00:00:00 2001
+From: Ian Jackson <ian.jackson@eu.citrix.com>
+Date: Mon, 14 Nov 2016 17:19:46 +0000
+Subject: [PATCH] qemu: ioport_read, ioport_write: be defensive about 32-bit
+ addresses
+
+On x86, ioport addresses are 16-bit.  That these functions take 32-bit
+arguments is a mistake.  Changing the argument type to 16-bit will
+discard the top bits of any erroneous values from elsewhere in qemu.
+
+Also, check just before use that the value is in range.  (This turns
+an ill-advised change to MAX_IOPORTS into a possible guest crash
+rather than a privilege escalation vulnerability.)
+
+And, in the Xen ioreq processor, clamp incoming ioport addresses to
+16-bit values.  Xen will never write >16-bit values but the guest may
+have access to the ioreq ring.  We want to defend the rest of the qemu
+code from wrong values.
+
+This is XSA-199.
+
+Reported-by: yanghongke <yanghongke@huawei.com>
+Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
+---
+ i386-dm/helper2.c | 2 ++
+ vl.c              | 9 +++++++--
+ 2 files changed, 9 insertions(+), 2 deletions(-)
+
+diff --git a/i386-dm/helper2.c b/i386-dm/helper2.c
+index 2706f2e..5d276bb 100644
+--- a/i386-dm/helper2.c
++++ b/i386-dm/helper2.c
+@@ -375,6 +375,8 @@ static void cpu_ioreq_pio(CPUState *env, ioreq_t *req)
+ {
+     uint32_t i;
+ 
++    req->addr &= 0x0ffffU;
++
+     if (req->dir == IOREQ_READ) {
+         if (!req->data_is_ptr) {
+             req->data = do_inp(env, req->addr, req->size);
+diff --git a/vl.c b/vl.c
+index f9c4d7e..c3c5d63 100644
+--- a/vl.c
++++ b/vl.c
+@@ -52,6 +52,7 @@
+ 
+ #include <xen/hvm/hvm_info_table.h>
+ 
++#include <assert.h>
+ #include <unistd.h>
+ #include <fcntl.h>
+ #include <signal.h>
+@@ -290,26 +291,30 @@ PicState2 *isa_pic;
+ static IOPortReadFunc default_ioport_readb, default_ioport_readw, default_ioport_readl;
+ static IOPortWriteFunc default_ioport_writeb, default_ioport_writew, default_ioport_writel;
+ 
+-static uint32_t ioport_read(int index, uint32_t address)
++static uint32_t ioport_read(int index, uint16_t address)
+ {
+     static IOPortReadFunc *default_func[3] = {
+         default_ioport_readb,
+         default_ioport_readw,
+         default_ioport_readl
+     };
++    if (address >= MAX_IOPORTS)
++        abort();
+     IOPortReadFunc *func = ioport_read_table[index][address];
+     if (!func)
+         func = default_func[index];
+     return func(ioport_opaque[address], address);
+ }
+ 
+-static void ioport_write(int index, uint32_t address, uint32_t data)
++static void ioport_write(int index, uint16_t address, uint32_t data)
+ {
+     static IOPortWriteFunc *default_func[3] = {
+         default_ioport_writeb,
+         default_ioport_writew,
+         default_ioport_writel
+     };
++    if (address >= MAX_IOPORTS)
++        abort();
+     IOPortWriteFunc *func = ioport_write_table[index][address];
+     if (!func)
+         func = default_func[index];
+-- 
+2.1.4
+
diff --git a/system/xen/xsa/xsa200-4.7.patch b/system/xen/xsa/xsa200-4.7.patch
new file mode 100644
index 0000000000..69608f6fc3
--- /dev/null
+++ b/system/xen/xsa/xsa200-4.7.patch
@@ -0,0 +1,55 @@
+From: Jan Beulich <jbeulich@suse.com>
+Subject: x86emul: CMPXCHG8B ignores operand size prefix
+
+Otherwise besides mis-handling the instruction, the comparison failure
+case would result in uninitialized stack data being handed back to the
+guest in rDX:rAX (32 bits leaked for 32-bit guests, 96 bits for 64-bit
+ones).
+
+This is XSA-200.
+
+Signed-off-by: Jan Beulich <jbeulich@suse.com>
+
+--- a/tools/tests/x86_emulator/test_x86_emulator.c
++++ b/tools/tests/x86_emulator/test_x86_emulator.c
+@@ -435,6 +435,24 @@ int main(int argc, char **argv)
+         goto fail;
+     printf("okay\n");
+ 
++    printf("%-40s", "Testing cmpxchg8b (%edi) [opsize]...");
++    instr[0] = 0x66; instr[1] = 0x0f; instr[2] = 0xc7; instr[3] = 0x0f;
++    res[0]      = 0x12345678;
++    res[1]      = 0x87654321;
++    regs.eflags = 0x200;
++    regs.eip    = (unsigned long)&instr[0];
++    regs.edi    = (unsigned long)res;
++    rc = x86_emulate(&ctxt, &emulops);
++    if ( (rc != X86EMUL_OKAY) ||
++         (res[0] != 0x12345678) ||
++         (res[1] != 0x87654321) ||
++         (regs.eax != 0x12345678) ||
++         (regs.edx != 0x87654321) ||
++         ((regs.eflags&0x240) != 0x200) ||
++         (regs.eip != (unsigned long)&instr[4]) )
++        goto fail;
++    printf("okay\n");
++
+     printf("%-40s", "Testing movsxbd (%%eax),%%ecx...");
+     instr[0] = 0x0f; instr[1] = 0xbe; instr[2] = 0x08;
+     regs.eflags = 0x200;
+--- a/xen/arch/x86/x86_emulate/x86_emulate.c
++++ b/xen/arch/x86/x86_emulate/x86_emulate.c
+@@ -4775,8 +4775,12 @@ x86_emulate(
+         generate_exception_if((modrm_reg & 7) != 1, EXC_UD, -1);
+         generate_exception_if(ea.type != OP_MEM, EXC_UD, -1);
+         if ( op_bytes == 8 )
++        {
+             host_and_vcpu_must_have(cx16);
+-        op_bytes *= 2;
++            op_bytes = 16;
++        }
++        else
++            op_bytes = 8;
+ 
+         /* Get actual old value. */
+         if ( (rc = ops->read(ea.mem.seg, ea.mem.off, old, op_bytes,
diff --git a/system/xen/xsa/xsa201-1.patch b/system/xen/xsa/xsa201-1.patch
new file mode 100644
index 0000000000..50983b852f
--- /dev/null
+++ b/system/xen/xsa/xsa201-1.patch
@@ -0,0 +1,87 @@
+From: Wei Chen <Wei.Chen@arm.com>
+Subject: arm64: handle guest-generated EL1 asynchronous abort
+
+In current code, when the hypervisor receives an asynchronous abort
+from a guest, the hypervisor will do panic, the host will be down.
+We have to prevent such security issue, so, in this patch we crash
+the guest, when the hypervisor receives an asynchronous abort from
+the guest.
+
+This is CVE-2016-9815, part of XSA-201.
+
+Signed-off-by: Wei Chen <Wei.Chen@arm.com>
+Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
+Reviewed-by: Steve Capper <steve.capper@arm.com>
+Reviewed-by: Julien Grall <Julien.Grall@arm.com>
+
+--- a/xen/arch/arm/arm64/entry.S
++++ b/xen/arch/arm/arm64/entry.S
+@@ -204,9 +204,12 @@ guest_fiq_invalid:
+         entry   hyp=0, compat=0
+         invalid BAD_FIQ
+
+-guest_error_invalid:
++guest_error:
+         entry   hyp=0, compat=0
+-        invalid BAD_ERROR
++        msr     daifclr, #2
++        mov     x0, sp
++        bl      do_trap_guest_error
++        exit    hyp=0, compat=0
+
+ guest_sync_compat:
+         entry   hyp=0, compat=1
+@@ -225,9 +228,12 @@ guest_fiq_invalid_compat:
+         entry   hyp=0, compat=1
+         invalid BAD_FIQ
+
+-guest_error_invalid_compat:
++guest_error_compat:
+         entry   hyp=0, compat=1
+-        invalid BAD_ERROR
++        msr     daifclr, #2
++        mov     x0, sp
++        bl      do_trap_guest_error
++        exit    hyp=0, compat=1
+
+ ENTRY(return_to_new_vcpu32)
+         exit    hyp=0, compat=1
+@@ -286,12 +292,12 @@ ENTRY(hyp_traps_vector)
+         ventry  guest_sync                      // Synchronous 64-bit EL0/EL1
+         ventry  guest_irq                       // IRQ 64-bit EL0/EL1
+         ventry  guest_fiq_invalid               // FIQ 64-bit EL0/EL1
+-        ventry  guest_error_invalid             // Error 64-bit EL0/EL1
++        ventry  guest_error                     // Error 64-bit EL0/EL1
+
+         ventry  guest_sync_compat               // Synchronous 32-bit EL0/EL1
+         ventry  guest_irq_compat                // IRQ 32-bit EL0/EL1
+         ventry  guest_fiq_invalid_compat        // FIQ 32-bit EL0/EL1
+-        ventry  guest_error_invalid_compat      // Error 32-bit EL0/EL1
++        ventry  guest_error_compat              // Error 32-bit EL0/EL1
+
+ /*
+  * struct vcpu *__context_switch(struct vcpu *prev, struct vcpu *next)
+--- a/xen/arch/arm/traps.c
++++ b/xen/arch/arm/traps.c
+@@ -2723,6 +2723,21 @@ asmlinkage void do_trap_hypervisor(struct cpu_user_regs *regs)
+     }
+ }
+
++asmlinkage void do_trap_guest_error(struct cpu_user_regs *regs)
++{
++    enter_hypervisor_head(regs);
++
++    /*
++     * Currently, to ensure hypervisor safety, when we received a
++     * guest-generated vSerror/vAbort, we just crash the guest to protect
++     * the hypervisor. In future we can better handle this by injecting
++     * a vSerror/vAbort to the guest.
++     */
++    gdprintk(XENLOG_WARNING, "Guest(Dom-%u) will be crashed by vSError\n",
++             current->domain->domain_id);
++    domain_crash_synchronous();
++}
++
+ asmlinkage void do_trap_irq(struct cpu_user_regs *regs)
+ {
+     enter_hypervisor_head(regs);
diff --git a/system/xen/xsa/xsa201-2.patch b/system/xen/xsa/xsa201-2.patch
new file mode 100644
index 0000000000..9bd1f8f89d
--- /dev/null
+++ b/system/xen/xsa/xsa201-2.patch
@@ -0,0 +1,199 @@
+From: Wei Chen <Wei.Chen@arm.com>
+Subject: arm64: handle async aborts delivered while at EL2
+
+If EL1 generates an asynchronous abort and then traps into EL2
+(by HVC or IRQ) before the abort has been delivered, the hypervisor
+could not catch it, because the PSTATE.A bit is masked all the time
+in hypervisor. So this asynchronous abort may be slipped to next
+running guest with PSTATE.A bit unmasked.
+
+In order to avoid this, it is necessary to take the abort at EL2, by
+clearing the PSTATE.A bit. In this patch, we unmask the PSTATE.A bit
+to open a window to catch guest-generated asynchronous abort in all
+EL1 -> EL2 swich paths. If we catched such asynchronous abort in
+checking window, the hyp_error exception will be triggered and the
+abort source guest will be crashed.
+
+This is CVE-2016-9816, part of XSA-201.
+
+Signed-off-by: Wei Chen <Wei.Chen@arm.com>
+Reviewed-by: Julien Grall <julien.grall@arm.com>
+
+--- a/xen/arch/arm/arm64/entry.S
++++ b/xen/arch/arm/arm64/entry.S
+@@ -173,6 +173,43 @@ hyp_error_invalid:
+         entry   hyp=1
+         invalid BAD_ERROR
+
++hyp_error:
++        /*
++         * Only two possibilities:
++         * 1) Either we come from the exit path, having just unmasked
++         *    PSTATE.A: change the return code to an EL2 fault, and
++         *    carry on, as we're already in a sane state to handle it.
++         * 2) Or we come from anywhere else, and that's a bug: we panic.
++         */
++        entry   hyp=1
++        msr     daifclr, #2
++
++        /*
++         * The ELR_EL2 may be modified by an interrupt, so we have to use the
++         * saved value in cpu_user_regs to check whether we come from 1) or
++         * not.
++         */
++        ldr     x0, [sp, #UREGS_PC]
++        adr     x1, abort_guest_exit_start
++        cmp     x0, x1
++        adr     x1, abort_guest_exit_end
++        ccmp    x0, x1, #4, ne
++        mov     x0, sp
++        mov     x1, #BAD_ERROR
++
++        /*
++         * Not equal, the exception come from 2). It's a bug, we have to
++         * panic the hypervisor.
++         */
++        b.ne    do_bad_mode
++
++        /*
++         * Otherwise, the exception come from 1). It happened because of
++         * the guest. Crash this guest.
++         */
++        bl      do_trap_guest_error
++        exit    hyp=1
++
+ /* Traps taken in Current EL with SP_ELx */
+ hyp_sync:
+         entry   hyp=1
+@@ -189,15 +226,29 @@ hyp_irq:
+
+ guest_sync:
+         entry   hyp=0, compat=0
++        bl      check_pending_vserror
++        /*
++         * If x0 is Non-zero, a vSError took place, the initial exception
++         * doesn't have any significance to be handled. Exit ASAP
++         */
++        cbnz    x0, 1f
+         msr     daifclr, #2
+         mov     x0, sp
+         bl      do_trap_hypervisor
++1:
+         exit    hyp=0, compat=0
+
+ guest_irq:
+         entry   hyp=0, compat=0
++        bl      check_pending_vserror
++        /*
++         * If x0 is Non-zero, a vSError took place, the initial exception
++         * doesn't have any significance to be handled. Exit ASAP
++         */
++        cbnz    x0, 1f
+         mov     x0, sp
+         bl      do_trap_irq
++1:
+         exit    hyp=0, compat=0
+
+ guest_fiq_invalid:
+@@ -213,15 +264,29 @@ guest_error:
+
+ guest_sync_compat:
+         entry   hyp=0, compat=1
++        bl      check_pending_vserror
++        /*
++         * If x0 is Non-zero, a vSError took place, the initial exception
++         * doesn't have any significance to be handled. Exit ASAP
++         */
++        cbnz    x0, 1f
+         msr     daifclr, #2
+         mov     x0, sp
+         bl      do_trap_hypervisor
++1:
+         exit    hyp=0, compat=1
+
+ guest_irq_compat:
+         entry   hyp=0, compat=1
++        bl      check_pending_vserror
++        /*
++         * If x0 is Non-zero, a vSError took place, the initial exception
++         * doesn't have any significance to be handled. Exit ASAP
++         */
++        cbnz    x0, 1f
+         mov     x0, sp
+         bl      do_trap_irq
++1:
+         exit    hyp=0, compat=1
+
+ guest_fiq_invalid_compat:
+@@ -270,6 +335,62 @@ return_from_trap:
+         eret
+
+ /*
++ * This function is used to check pending virtual SError in the gap of
++ * EL1 -> EL2 world switch.
++ * The x0 register will be used to indicate the results of detection.
++ * x0 -- Non-zero indicates a pending virtual SError took place.
++ * x0 -- Zero indicates no pending virtual SError took place.
++ */
++check_pending_vserror:
++        /*
++         * Save elr_el2 to check whether the pending SError exception takes
++         * place while we are doing this sync exception.
++         */
++        mrs     x0, elr_el2
++
++        /* Synchronize against in-flight ld/st */
++        dsb     sy
++
++        /*
++         * Unmask PSTATE asynchronous abort bit. If there is a pending
++         * SError, the EL2 error exception will happen after PSTATE.A
++         * is cleared.
++         */
++        msr     daifclr, #4
++
++        /*
++         * This is our single instruction exception window. A pending
++         * SError is guaranteed to occur at the earliest when we unmask
++         * it, and at the latest just after the ISB.
++         *
++         * If a pending SError occurs, the program will jump to EL2 error
++         * exception handler, and the elr_el2 will be set to
++         * abort_guest_exit_start or abort_guest_exit_end.
++         */
++abort_guest_exit_start:
++
++        isb
++
++abort_guest_exit_end:
++        /* Mask PSTATE asynchronous abort bit, close the checking window. */
++        msr     daifset, #4
++
++        /*
++         * Compare elr_el2 and the saved value to check whether we are
++         * returning from a valid exception caused by pending SError.
++         */
++        mrs     x1, elr_el2
++        cmp     x0, x1
++
++        /*
++         * Not equal, the pending SError exception took place, set
++         * x0 to non-zero.
++         */
++        cset    x0, ne
++
++        ret
++
++/*
+  * Exception vectors.
+  */
+         .macro  ventry  label
+@@ -287,7 +408,7 @@ ENTRY(hyp_traps_vector)
+         ventry  hyp_sync                        // Synchronous EL2h
+         ventry  hyp_irq                         // IRQ EL2h
+         ventry  hyp_fiq_invalid                 // FIQ EL2h
+-        ventry  hyp_error_invalid               // Error EL2h
++        ventry  hyp_error                       // Error EL2h
+
+         ventry  guest_sync                      // Synchronous 64-bit EL0/EL1
+         ventry  guest_irq                       // IRQ 64-bit EL0/EL1
diff --git a/system/xen/xsa/xsa201-3-4.7.patch b/system/xen/xsa/xsa201-3-4.7.patch
new file mode 100644
index 0000000000..af7fc3703e
--- /dev/null
+++ b/system/xen/xsa/xsa201-3-4.7.patch
@@ -0,0 +1,47 @@
+From: Wei Chen <Wei.Chen@arm.com>
+Subject: arm: crash the guest when it traps on external abort
+
+If we spot a data or prefetch abort bearing the ESR_EL2.EA bit set, we
+know that this is an external abort, and that should crash the guest.
+
+This is CVE-2016-9817, part of XSA-201.
+
+Signed-off-by: Wei Chen <Wei.Chen@arm.com>
+Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
+Reviewed-by: Steve Capper <steve.capper@arm.com>
+Reviewed-by: Julien Grall <Julien.Grall@arm.com>
+
+--- a/xen/arch/arm/traps.c
++++ b/xen/arch/arm/traps.c
+@@ -2383,6 +2383,15 @@ static void do_trap_instr_abort_guest(struct cpu_user_regs *regs,
+     int rc;
+     register_t gva = READ_SYSREG(FAR_EL2);
+ 
++    /*
++     * If this bit has been set, it means that this instruction abort is caused
++     * by a guest external abort. Currently we crash the guest to protect the
++     * hypervisor. In future one can better handle this by injecting a virtual
++     * abort to the guest.
++     */
++    if ( hsr.iabt.eat )
++        domain_crash_synchronous();
++
+     switch ( hsr.iabt.ifsc & 0x3f )
+     {
+     case FSC_FLT_PERM ... FSC_FLT_PERM + 3:
+@@ -2437,6 +2446,15 @@ static void do_trap_data_abort_guest(struct cpu_user_regs *regs,
+         return;
+     }
+ 
++    /*
++     * If this bit has been set, it means that this data abort is caused
++     * by a guest external abort. Currently we crash the guest to protect the
++     * hypervisor. In future one can better handle this by injecting a virtual
++     * abort to the guest.
++     */
++    if ( dabt.eat )
++        domain_crash_synchronous();
++
+     info.dabt = dabt;
+ #ifdef CONFIG_ARM_32
+     info.gva = READ_CP32(HDFAR);
diff --git a/system/xen/xsa/xsa201-4.patch b/system/xen/xsa/xsa201-4.patch
new file mode 100644
index 0000000000..8060a5be13
--- /dev/null
+++ b/system/xen/xsa/xsa201-4.patch
@@ -0,0 +1,130 @@
+From: Wei Chen <Wei.Chen@arm.com>
+Subject: arm32: handle async aborts delivered while at HYP
+
+If guest generates an asynchronous abort and then traps into HYP
+(by HVC or IRQ) before the abort has been delivered, the hypervisor
+could not catch it, because the PSTATE.A bit is masked all the time
+in hypervisor. So this asynchronous abort may be slipped to next
+running guest with PSTATE.A bit unmasked.
+
+In order to avoid this, it is necessary to take the abort at HYP, by
+clearing the PSTATE.A bit. In this patch, we unmask the PSTATE.A bit
+to open a window to catch guest-generated asynchronous abort in all
+Guest -> HYP switch paths. If we caught such asynchronous abort in
+checking window, the HYP data abort exception will be triggered and
+the abort source guest will be crashed.
+
+This is CVE-2016-9818, part of XSA-201.
+
+Signed-off-by: Wei Chen <Wei.Chen@arm.com>
+Reviewed-by: Julien Grall <julien.grall@arm.com>
+
+--- a/xen/arch/arm/arm32/entry.S
++++ b/xen/arch/arm/arm32/entry.S
+@@ -42,6 +42,61 @@ save_guest_regs:
+         SAVE_BANKED(fiq)
+         SAVE_ONE_BANKED(R8_fiq); SAVE_ONE_BANKED(R9_fiq); SAVE_ONE_BANKED(R10_fiq)
+         SAVE_ONE_BANKED(R11_fiq); SAVE_ONE_BANKED(R12_fiq);
++        /*
++         * Start to check pending virtual abort in the gap of Guest -> HYP
++         * world switch.
++         *
++         * Save ELR_hyp to check whether the pending virtual abort exception
++         * takes place while we are doing this trap exception.
++         */
++        mrs r1, ELR_hyp
++
++        /*
++         * Force loads and stores to complete before unmasking asynchronous
++         * aborts and forcing the delivery of the exception.
++         */
++        dsb sy
++
++        /*
++         * Unmask asynchronous abort bit. If there is a pending asynchronous
++         * abort, the data_abort exception will happen after A bit is cleared.
++         */
++        cpsie a
++
++        /*
++         * This is our single instruction exception window. A pending
++         * asynchronous abort is guaranteed to occur at the earliest when we
++         * unmask it, and at the latest just after the ISB.
++         *
++         * If a pending abort occurs, the program will jump to data_abort
++         * exception handler, and the ELR_hyp will be set to
++         * abort_guest_exit_start or abort_guest_exit_end.
++         */
++        .global abort_guest_exit_start
++abort_guest_exit_start:
++
++        isb
++
++        .global abort_guest_exit_end
++abort_guest_exit_end:
++        /* Mask CPSR asynchronous abort bit, close the checking window. */
++        cpsid a
++
++        /*
++         * Compare ELR_hyp and the saved value to check whether we are
++         * returning from a valid exception caused by pending virtual
++         * abort.
++         */
++        mrs r2, ELR_hyp
++        cmp r1, r2
++
++        /*
++         * Not equal, the pending virtual abort exception took place, the
++         * initial exception does not have any significance to be handled.
++         * Exit ASAP.
++         */
++        bne return_from_trap
++
+         mov pc, lr
+
+ #define DEFINE_TRAP_ENTRY(trap)                                         \
+--- a/xen/arch/arm/arm32/traps.c
++++ b/xen/arch/arm/arm32/traps.c
+@@ -63,7 +63,10 @@ asmlinkage void do_trap_prefetch_abort(struct cpu_user_regs *regs)
+
+ asmlinkage void do_trap_data_abort(struct cpu_user_regs *regs)
+ {
+-    do_unexpected_trap("Data Abort", regs);
++    if ( VABORT_GEN_BY_GUEST(regs) )
++        do_trap_guest_error(regs);
++    else
++        do_unexpected_trap("Data Abort", regs);
+ }
+
+ /*
+--- a/xen/include/asm-arm/arm32/processor.h
++++ b/xen/include/asm-arm/arm32/processor.h
+@@ -55,6 +55,17 @@ struct cpu_user_regs
+
+     uint32_t pad1; /* Doubleword-align the user half of the frame */
+ };
++
++/* Functions for pending virtual abort checking window. */
++void abort_guest_exit_start(void);
++void abort_guest_exit_end(void);
++
++#define VABORT_GEN_BY_GUEST(r)  \
++( \
++    ( (unsigned long)abort_guest_exit_start == (r)->pc ) || \
++    ( (unsigned long)abort_guest_exit_end == (r)->pc ) \
++)
++
+ #endif
+
+ /* Layout as used in assembly, with src/dest registers mixed in */
+--- a/xen/include/asm-arm/processor.h
++++ b/xen/include/asm-arm/processor.h
+@@ -690,6 +690,8 @@ void vcpu_regs_user_to_hyp(struct vcpu *vcpu,
+ int call_smc(register_t function_id, register_t arg0, register_t arg1,
+              register_t arg2);
+
++void do_trap_guest_error(struct cpu_user_regs *regs);
++
+ #endif /* __ASSEMBLY__ */
+ #endif /* __ASM_ARM_PROCESSOR_H */
+ /*