[PATCH v3 0/2] various aarch64 fixes for running Hyper-V on TCG

[PATCH v3 0/2] various aarch64 fixes for running Hyper-V on TCG

[Evgeny Iakovlev]

Small series of changes to aarch64 emulation to better support running
Hyper-V as a TCG guest wtih EL3 firmware.

v3:
* Replaced raw_write fn with raw_write instead of a manual function

v2:
* DBGCLAIM now implements a (trivial) raw_write handler
* Added comments around ignored external debug registers
* Patch 3 is dropped because it was manually picked into target-arm.next

Evgeny Iakovlev (2):
  target/arm: implement DBGCLAIM registers
  target/arm: provide stubs for more external debug registers

 target/arm/cpu.h          |  1 +
 target/arm/debug_helper.c | 54 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)

-- 
2.34.1

[PATCH v3 1/2] target/arm: implement DBGCLAIM registers

[Evgeny Iakovlev]

The architecture does not define any functionality for the CLAIM tag bits.
So we will just keep the raw bits, as per spec.

Signed-off-by: Evgeny Iakovlev <eiakovlev@linux.microsoft.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/arm/cpu.h          |  1 +
 target/arm/debug_helper.c | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index bf2bce046d..d1ad0939ca 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -495,6 +495,7 @@ typedef struct CPUArchState {
         uint64_t dbgbcr[16]; /* breakpoint control registers */
         uint64_t dbgwvr[16]; /* watchpoint value registers */
         uint64_t dbgwcr[16]; /* watchpoint control registers */
+        uint64_t dbgclaim;   /* DBGCLAIM bits */
         uint64_t mdscr_el1;
         uint64_t oslsr_el1; /* OS Lock Status */
         uint64_t osdlr_el1; /* OS DoubleLock status */
diff --git a/target/arm/debug_helper.c b/target/arm/debug_helper.c
index 2f6ddc0da5..f95a73329d 100644
--- a/target/arm/debug_helper.c
+++ b/target/arm/debug_helper.c
@@ -632,6 +632,24 @@ static void osdlr_write(CPUARMState *env, const ARMCPRegInfo *ri,
     }
 }
 
+static void dbgclaimset_write(CPUARMState *env, const ARMCPRegInfo *ri,
+                              uint64_t value)
+{
+    env->cp15.dbgclaim |= (value & 0xFF);
+}
+
+static uint64_t dbgclaimset_read(CPUARMState *env, const ARMCPRegInfo *ri)
+{
+    /* CLAIM bits are RAO */
+    return 0xFF;
+}
+
+static void dbgclaimclr_write(CPUARMState *env, const ARMCPRegInfo *ri,
+                              uint64_t value)
+{
+    env->cp15.dbgclaim &= ~(value & 0xFF);
+}
+
 static const ARMCPRegInfo debug_cp_reginfo[] = {
     /*
      * DBGDRAR, DBGDSAR: always RAZ since we don't implement memory mapped
@@ -715,6 +733,21 @@ static const ARMCPRegInfo debug_cp_reginfo[] = {
       .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 0, .crm = 2, .opc2 = 0,
       .access = PL1_RW, .accessfn = access_tda,
       .type = ARM_CP_NOP },
+    /*
+     * Dummy DBGCLAIM registers.
+     * "The architecture does not define any functionality for the CLAIM tag bits.",
+     * so we only keep the raw bits
+     */
+    { .name = "DBGCLAIMSET_EL1", .state = ARM_CP_STATE_BOTH,
+      .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 7, .crm = 8, .opc2 = 6,
+      .type = ARM_CP_ALIAS,
+      .access = PL1_RW, .accessfn = access_tda,
+      .writefn = dbgclaimset_write, .readfn = dbgclaimset_read },
+    { .name = "DBGCLAIMCLR_EL1", .state = ARM_CP_STATE_BOTH,
+      .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 7, .crm = 9, .opc2 = 6,
+      .access = PL1_RW, .accessfn = access_tda,
+      .writefn = dbgclaimclr_write, .raw_writefn = raw_write,
+      .fieldoffset = offsetof(CPUARMState, cp15.dbgclaim) },
 };
 
 static const ARMCPRegInfo debug_lpae_cp_reginfo[] = {
-- 
2.34.1

[PATCH v3 2/2] target/arm: provide stubs for more external debug registers

[Evgeny Iakovlev]

Qemu doesn't implement Debug Communication Channel, as well as the rest
of external debug interface. However, Microsoft Hyper-V in tries to
access some of those registers during an EL2 context switch.

Since there is no architectural way to not advertise support for external
debug, provide RAZ/WI stubs for OSDTRRX_EL1, OSDTRTX_EL1 and OSECCR_EL1
registers in the same way the rest of DCM is currently done. Do account
for access traps though with access_tda.

Signed-off-by: Evgeny Iakovlev <eiakovlev@linux.microsoft.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/debug_helper.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/target/arm/debug_helper.c b/target/arm/debug_helper.c
index f95a73329d..cced3f168d 100644
--- a/target/arm/debug_helper.c
+++ b/target/arm/debug_helper.c
@@ -682,6 +682,27 @@ static const ARMCPRegInfo debug_cp_reginfo[] = {
       .opc0 = 2, .opc1 = 3, .crn = 0, .crm = 1, .opc2 = 0,
       .access = PL0_R, .accessfn = access_tda,
       .type = ARM_CP_CONST, .resetvalue = 0 },
+    /*
+     * OSDTRRX_EL1/OSDTRTX_EL1 are used for save and restore of DBGDTRRX_EL0.
+     * It is a component of the Debug Communications Channel, which is not implemented.
+     */
+    { .name = "OSDTRRX_EL1", .state = ARM_CP_STATE_BOTH, .cp = 14,
+      .opc0 = 2, .opc1 = 0, .crn = 0, .crm = 0, .opc2 = 2,
+      .access = PL1_RW, .accessfn = access_tda,
+      .type = ARM_CP_CONST, .resetvalue = 0 },
+    { .name = "OSDTRTX_EL1", .state = ARM_CP_STATE_BOTH, .cp = 14,
+      .opc0 = 2, .opc1 = 0, .crn = 0, .crm = 3, .opc2 = 2,
+      .access = PL1_RW, .accessfn = access_tda,
+      .type = ARM_CP_CONST, .resetvalue = 0 },
+    /*
+     * OSECCR_EL1 provides a mechanism for an operating system
+     * to access the contents of EDECCR. EDECCR is not implemented though,
+     * as is the rest of external device mechanism.
+     */
+    { .name = "OSECCR_EL1", .state = ARM_CP_STATE_BOTH, .cp = 14,
+      .opc0 = 2, .opc1 = 0, .crn = 0, .crm = 6, .opc2 = 2,
+      .access = PL1_RW, .accessfn = access_tda,
+      .type = ARM_CP_CONST, .resetvalue = 0 },
     /*
      * DBGDSCRint[15,12,5:2] map to MDSCR_EL1[15,12,5:2].  Map all bits as
      * it is unlikely a guest will care.
-- 
2.34.1

Re: [PATCH v3 0/2] various aarch64 fixes for running Hyper-V on TCG

[Peter Maydell]

On Fri, 20 Jan 2023 at 15:59, Evgeny Iakovlev
<eiakovlev@linux.microsoft.com> wrote:
>
> Small series of changes to aarch64 emulation to better support running
> Hyper-V as a TCG guest wtih EL3 firmware.



Applied to target-arm.next, thanks.

-- PMM