[xen staging] xen/arm: io: Abstract sign-extension

[patchbot@xxxxxxx]

commit 56608aecfb41a54aca85e11147e1c73903f38acf
Author:     Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
AuthorDate: Fri Jan 29 03:48:47 2021 +0200
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Fri Jan 29 16:55:41 2021 +0000

    xen/arm: io: Abstract sign-extension
    
    In order to avoid code duplication (both handle_read() and
    handle_ioserv() contain the same code for the sign-extension)
    put this code to a common helper to be used for both.
    
    Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
    CC: Julien Grall <julien.grall@xxxxxxx>
    Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
    [On Arm only]
    Tested-by: Wei Chen <Wei.Chen@xxxxxxx>
---
 xen/arch/arm/io.c           | 18 ++----------------
 xen/arch/arm/ioreq.c        | 17 +----------------
 xen/include/asm-arm/traps.h | 24 ++++++++++++++++++++++++
 3 files changed, 27 insertions(+), 32 deletions(-)

diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
index 7ac03037ea..729287e37c 100644
--- a/xen/arch/arm/io.c
+++ b/xen/arch/arm/io.c
@@ -25,6 +25,7 @@
 #include <asm/current.h>
 #include <asm/ioreq.h>
 #include <asm/mmio.h>
+#include <asm/traps.h>
 
 #include "decode.h"
 
@@ -40,26 +41,11 @@ static enum io_state handle_read(const struct mmio_handler 
*handler,
      * setting r).
      */
     register_t r = 0;
-    uint8_t size = (1 << dabt.size) * 8;
 
     if ( !handler->ops->read(v, info, &r, handler->priv) )
         return IO_ABORT;
 
-    /*
-     * Sign extend if required.
-     * Note that we expect the read handler to have zeroed the bits
-     * outside the requested access size.
-     */
-    if ( dabt.sign && (r & (1UL << (size - 1))) )
-    {
-        /*
-         * We are relying on register_t using the same as
-         * an unsigned long in order to keep the 32-bit assembly
-         * code smaller.
-         */
-        BUILD_BUG_ON(sizeof(register_t) != sizeof(unsigned long));
-        r |= (~0UL) << size;
-    }
+    r = sign_extend(dabt, r);
 
     set_user_reg(regs, dabt.reg, r);
 
diff --git a/xen/arch/arm/ioreq.c b/xen/arch/arm/ioreq.c
index 43f5d6b782..308650b400 100644
--- a/xen/arch/arm/ioreq.c
+++ b/xen/arch/arm/ioreq.c
@@ -28,7 +28,6 @@ enum io_state handle_ioserv(struct cpu_user_regs *regs, 
struct vcpu *v)
     const union hsr hsr = { .bits = regs->hsr };
     const struct hsr_dabt dabt = hsr.dabt;
     /* Code is similar to handle_read */
-    uint8_t size = (1 << dabt.size) * 8;
     register_t r = v->io.req.data;
 
     /* We are done with the IO */
@@ -37,21 +36,7 @@ enum io_state handle_ioserv(struct cpu_user_regs *regs, 
struct vcpu *v)
     if ( dabt.write )
         return IO_HANDLED;
 
-    /*
-     * Sign extend if required.
-     * Note that we expect the read handler to have zeroed the bits
-     * outside the requested access size.
-     */
-    if ( dabt.sign && (r & (1UL << (size - 1))) )
-    {
-        /*
-         * We are relying on register_t using the same as
-         * an unsigned long in order to keep the 32-bit assembly
-         * code smaller.
-         */
-        BUILD_BUG_ON(sizeof(register_t) != sizeof(unsigned long));
-        r |= (~0UL) << size;
-    }
+    r = sign_extend(dabt, r);
 
     set_user_reg(regs, dabt.reg, r);
 
diff --git a/xen/include/asm-arm/traps.h b/xen/include/asm-arm/traps.h
index c4a3d0fb1b..c6b3cc75ca 100644
--- a/xen/include/asm-arm/traps.h
+++ b/xen/include/asm-arm/traps.h
@@ -84,6 +84,30 @@ static inline bool VABORT_GEN_BY_GUEST(const struct 
cpu_user_regs *regs)
         (unsigned long)abort_guest_exit_end == regs->pc;
 }
 
+/* Check whether the sign extension is required and perform it */
+static inline register_t sign_extend(const struct hsr_dabt dabt, register_t r)
+{
+    uint8_t size = (1 << dabt.size) * 8;
+
+    /*
+     * Sign extend if required.
+     * Note that we expect the read handler to have zeroed the bits
+     * outside the requested access size.
+     */
+    if ( dabt.sign && (r & (1UL << (size - 1))) )
+    {
+        /*
+         * We are relying on register_t using the same as
+         * an unsigned long in order to keep the 32-bit assembly
+         * code smaller.
+         */
+        BUILD_BUG_ON(sizeof(register_t) != sizeof(unsigned long));
+        r |= (~0UL) << size;
+    }
+
+    return r;
+}
+
 #endif /* __ASM_ARM_TRAPS__ */
 /*
  * Local variables:
--
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