[Qemu-devel] [PATCHv4] target-arm: Implement AArch64 OSLAR/OSLSR_EL1 sysregs

[Qemu-devel] [PATCHv4] target-arm: Implement AArch64 OSLAR/OSLSR_EL1 sysregs

[Davorin Mista]

Added oslar_write function to OSLAR_EL1 sysreg, using a status variable
in ARMCPUState.cp15 struct (oslsr_el1). This variable is also linked
to the newly added read-only OSLSR_EL1 register.

Linux reads from this register during its suspend/resume procedure.

Signed-off-by: Davorin Mista <davorin.mista@aggios.com>

---
Changed in v2:
-switched from using dummy registers to an actual register implementation
-implemented write function for OSLAR_EL1 sysreg
-added state variable to ARMCPUState struct

Changed in v3:
-renamed variable to oslsr_el1 and moved to cp15
-renamed write frunction to oslar_write
-support both 32bit and 64bit ARM in oslar_write
-moved resetvalue to the corresponding read-only register
-removed "dummy" comments above registers

Changed in v4:
-added type = ARM_CP_NO_RAW
-removed fieldOffset for OSLAR register
-tested with QEMU mainline (git.qemu.org/qemu.git)
---
 target-arm/cpu.h    |  1 +
 target-arm/helper.c | 22 ++++++++++++++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index cc1578c..9b80c26 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -378,6 +378,7 @@ typedef struct CPUARMState {
         uint64_t dbgwvr[16]; /* watchpoint value registers */
         uint64_t dbgwcr[16]; /* watchpoint control registers */
         uint64_t mdscr_el1;
+        uint64_t oslsr_el1; /* OS Lock Status */
         /* If the counter is enabled, this stores the last time the counter
          * was reset. Otherwise it stores the counter value
          */
diff --git a/target-arm/helper.c b/target-arm/helper.c
index 8367997..33a3e3f 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -3564,6 +3564,20 @@ static CPAccessResult ctr_el0_access(CPUARMState *env, const ARMCPRegInfo *ri)
     return CP_ACCESS_OK;
 }
 
+/* write to oslsr_el1 (OS lock status) state variable */
+static void oslar_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value)
+{
+    int oslock;
+
+    if (ri->state == ARM_CP_STATE_AA32) {
+        oslock = (value == 0xC5ACCE55);
+    } else {
+        oslock = value & 1;
+    }
+
+    env->cp15.oslsr_el1 = deposit32(env->cp15.oslsr_el1, 1, 1, oslock);
+}
+
 static const ARMCPRegInfo debug_cp_reginfo[] = {
     /* DBGDRAR, DBGDSAR: always RAZ since we don't implement memory mapped
      * debug components. The AArch64 version of DBGDRAR is named MDRAR_EL1;
@@ -3592,10 +3606,14 @@ static const ARMCPRegInfo debug_cp_reginfo[] = {
       .type = ARM_CP_ALIAS,
       .access = PL1_R,
       .fieldoffset = offsetof(CPUARMState, cp15.mdscr_el1), },
-    /* We define a dummy WI OSLAR_EL1, because Linux writes to it. */
     { .name = "OSLAR_EL1", .state = ARM_CP_STATE_BOTH,
       .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 1, .crm = 0, .opc2 = 4,
-      .access = PL1_W, .type = ARM_CP_NOP },
+      .access = PL1_W, .type = ARM_CP_NO_RAW,
+      .writefn = oslar_write },
+    { .name = "OSLSR_EL1", .state = ARM_CP_STATE_BOTH,
+      .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 1, .crm = 1, .opc2 = 4,
+      .access = PL1_R, .resetvalue = 10,
+      .fieldoffset = offsetof(CPUARMState, cp15.oslsr_el1) },
     /* Dummy OSDLR_EL1: 32-bit Linux will read this */
     { .name = "OSDLR_EL1", .state = ARM_CP_STATE_BOTH,
       .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 1, .crm = 3, .opc2 = 4,
-- 
2.6.0

Re: [Qemu-devel] [PATCHv4] target-arm: Implement AArch64 OSLAR/OSLSR_EL1 sysregs

[Peter Maydell]

On 6 October 2015 at 20:47, Davorin Mista <davorin.mista@aggios.com> wrote:
> Added oslar_write function to OSLAR_EL1 sysreg, using a status variable
> in ARMCPUState.cp15 struct (oslsr_el1). This variable is also linked
> to the newly added read-only OSLSR_EL1 register.
>
> Linux reads from this register during its suspend/resume procedure.
>
> Signed-off-by: Davorin Mista <davorin.mista@aggios.com>
>

Thanks. I folded a slightly overlong line and tweaked a comment,
and have applied this to target-arm.next.

-- PMM