diff mbox series

[v4,41/45] target/arm: Enable FEAT_CSV2_2 for -cpu max

Message ID 20220501055028.646596-42-richard.henderson@linaro.org
State Superseded
Headers show
Series target/arm: Cleanups, new features, new cpus | expand

Commit Message

Richard Henderson May 1, 2022, 5:50 a.m. UTC
There is no branch prediction in TCG, therefore there is no
need to actually include the context number into the predictor.
Therefore all we need to do is add the state for SCXTNUM_ELx.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v2: Update emulation.rst; clear CSV2_FRAC; use decimal; tidy access_scxtnum.
v3: Rely on EL3-no-EL2 squashing during registration.
---
 docs/system/arm/emulation.rst |  3 ++
 target/arm/cpu.h              | 16 +++++++++
 target/arm/cpu64.c            |  3 +-
 target/arm/helper.c           | 61 ++++++++++++++++++++++++++++++++++-
 4 files changed, 81 insertions(+), 2 deletions(-)

Comments

Peter Maydell May 3, 2022, 5:10 p.m. UTC | #1
On Sun, 1 May 2022 at 08:16, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> There is no branch prediction in TCG, therefore there is no
> need to actually include the context number into the predictor.
> Therefore all we need to do is add the state for SCXTNUM_ELx.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> v2: Update emulation.rst; clear CSV2_FRAC; use decimal; tidy access_scxtnum.
> v3: Rely on EL3-no-EL2 squashing during registration.
> ---
>  docs/system/arm/emulation.rst |  3 ++
>  target/arm/cpu.h              | 16 +++++++++
>  target/arm/cpu64.c            |  3 +-
>  target/arm/helper.c           | 61 ++++++++++++++++++++++++++++++++++-
>  4 files changed, 81 insertions(+), 2 deletions(-)

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

(The handling of SCXTNUM_EL0 should Just Work for user-mode-only,
right?)

thanks
-- PMM
Richard Henderson May 3, 2022, 7:33 p.m. UTC | #2
On 5/3/22 10:10, Peter Maydell wrote:
> On Sun, 1 May 2022 at 08:16, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>>
>> There is no branch prediction in TCG, therefore there is no
>> need to actually include the context number into the predictor.
>> Therefore all we need to do is add the state for SCXTNUM_ELx.
>>
>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>> v2: Update emulation.rst; clear CSV2_FRAC; use decimal; tidy access_scxtnum.
>> v3: Rely on EL3-no-EL2 squashing during registration.
>> ---
>>   docs/system/arm/emulation.rst |  3 ++
>>   target/arm/cpu.h              | 16 +++++++++
>>   target/arm/cpu64.c            |  3 +-
>>   target/arm/helper.c           | 61 ++++++++++++++++++++++++++++++++++-
>>   4 files changed, 81 insertions(+), 2 deletions(-)
> 
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> 
> (The handling of SCXTNUM_EL0 should Just Work for user-mode-only,
> right?)

Hmm, interesting.

The linux master does not support CSV2_1.2+.  This bit is supposed to be RES1 when the 
feature is not enabled, so when booted with TCG at EL1 access *should* be trapped, when 
the guest kernel is not buggy.  This falls into the

     /* ??? Lots of these bits are not implemented.  */


fixme in sctlr_write.  If the guest kernel is buggy... ya gets what ya gets.

We are particularly sloppy with SCTLR_EL1 with user-only; the res1 bits are not set,
which means that we'll expose the register at user-only.

Although context swapping is not an issue for user-only, I think we should not expose the 
value at this time.  It's plausible that the register will *never* be exposed to EL0.  We 
might get, for instance, a prctl to set a new thread/process-level random value instead.

Will provide a minimal user-only fix for v5, and work on sctlr_write another day.


r~
diff mbox series

Patch

diff --git a/docs/system/arm/emulation.rst b/docs/system/arm/emulation.rst
index b2a3e2a437..9765ee3eaf 100644
--- a/docs/system/arm/emulation.rst
+++ b/docs/system/arm/emulation.rst
@@ -13,6 +13,9 @@  the following architecture extensions:
 - FEAT_BF16 (AArch64 BFloat16 instructions)
 - FEAT_BTI (Branch Target Identification)
 - FEAT_CSV2 (Cache speculation variant 2)
+- FEAT_CSV2_1p1 (Cache speculation variant 2, version 1.1)
+- FEAT_CSV2_1p2 (Cache speculation variant 2, version 1.2)
+- FEAT_CSV2_2 (Cache speculation variant 2, version 2)
 - FEAT_DIT (Data Independent Timing instructions)
 - FEAT_DPB (DC CVAP instruction)
 - FEAT_Debugv8p2 (Debug changes for v8.2)
diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index aade9237bd..18ca61e8e2 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -688,6 +688,8 @@  typedef struct CPUArchState {
         ARMPACKey apdb;
         ARMPACKey apga;
     } keys;
+
+    uint64_t scxtnum_el[4];
 #endif
 
 #if defined(CONFIG_USER_ONLY)
@@ -1211,6 +1213,7 @@  void pmu_init(ARMCPU *cpu);
 #define SCTLR_WXN     (1U << 19)
 #define SCTLR_ST      (1U << 20) /* up to ??, RAZ in v6 */
 #define SCTLR_UWXN    (1U << 20) /* v7 onward, AArch32 only */
+#define SCTLR_TSCXT   (1U << 20) /* FEAT_CSV2_1p2, AArch64 only */
 #define SCTLR_FI      (1U << 21) /* up to v7, v8 RES0 */
 #define SCTLR_IESB    (1U << 21) /* v8.2-IESB, AArch64 only */
 #define SCTLR_U       (1U << 22) /* up to v6, RAO in v7 */
@@ -4022,6 +4025,19 @@  static inline bool isar_feature_aa64_dit(const ARMISARegisters *id)
     return FIELD_EX64(id->id_aa64pfr0, ID_AA64PFR0, DIT) != 0;
 }
 
+static inline bool isar_feature_aa64_scxtnum(const ARMISARegisters *id)
+{
+    int key = FIELD_EX64(id->id_aa64pfr0, ID_AA64PFR0, CSV2);
+    if (key >= 2) {
+        return true;      /* FEAT_CSV2_2 */
+    }
+    if (key == 1) {
+        key = FIELD_EX64(id->id_aa64pfr1, ID_AA64PFR1, CSV2_FRAC);
+        return key >= 2;  /* FEAT_CSV2_1p2 */
+    }
+    return false;
+}
+
 static inline bool isar_feature_aa64_ssbs(const ARMISARegisters *id)
 {
     return FIELD_EX64(id->id_aa64pfr1, ID_AA64PFR1, SSBS) != 0;
diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index 25fe74f928..07b44a62be 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -748,7 +748,7 @@  static void aarch64_max_initfn(Object *obj)
     t = FIELD_DP64(t, ID_AA64PFR0, SVE, 1);
     t = FIELD_DP64(t, ID_AA64PFR0, SEL2, 1);      /* FEAT_SEL2 */
     t = FIELD_DP64(t, ID_AA64PFR0, DIT, 1);       /* FEAT_DIT */
-    t = FIELD_DP64(t, ID_AA64PFR0, CSV2, 1);      /* FEAT_CSV2 */
+    t = FIELD_DP64(t, ID_AA64PFR0, CSV2, 2);      /* FEAT_CSV2_2 */
     cpu->isar.id_aa64pfr0 = t;
 
     t = cpu->isar.id_aa64pfr1;
@@ -760,6 +760,7 @@  static void aarch64_max_initfn(Object *obj)
      * we do for EL2 with the virtualization=on property.
      */
     t = FIELD_DP64(t, ID_AA64PFR1, MTE, 3);       /* FEAT_MTE3 */
+    t = FIELD_DP64(t, ID_AA64PFR1, CSV2_FRAC, 0); /* FEAT_CSV2_2 */
     cpu->isar.id_aa64pfr1 = t;
 
     t = cpu->isar.id_aa64mmfr0;
diff --git a/target/arm/helper.c b/target/arm/helper.c
index f62d16a456..7e31f11904 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -1770,6 +1770,9 @@  static void scr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value)
         if (cpu_isar_feature(aa64_mte, cpu)) {
             valid_mask |= SCR_ATA;
         }
+        if (cpu_isar_feature(aa64_scxtnum, cpu)) {
+            valid_mask |= SCR_ENSCXT;
+        }
     } else {
         valid_mask &= ~(SCR_RW | SCR_ST);
         if (cpu_isar_feature(aa32_ras, cpu)) {
@@ -5149,6 +5152,9 @@  static void do_hcr_write(CPUARMState *env, uint64_t value, uint64_t valid_mask)
         if (cpu_isar_feature(aa64_mte, cpu)) {
             valid_mask |= HCR_ATA | HCR_DCT | HCR_TID5;
         }
+        if (cpu_isar_feature(aa64_scxtnum, cpu)) {
+            valid_mask |= HCR_ENSCXT;
+        }
     }
 
     /* Clear RES0 bits.  */
@@ -5800,6 +5806,10 @@  static void define_arm_vh_e2h_redirects_aliases(ARMCPU *cpu)
         { K(3, 0,  5, 6, 0), K(3, 4,  5, 6, 0), K(3, 5, 5, 6, 0),
           "TFSR_EL1", "TFSR_EL2", "TFSR_EL12", isar_feature_aa64_mte },
 
+        { K(3, 0, 13, 0, 7), K(3, 4, 13, 0, 7), K(3, 5, 13, 0, 7),
+          "SCXTNUM_EL1", "SCXTNUM_EL2", "SCXTNUM_EL12",
+          isar_feature_aa64_scxtnum },
+
         /* TODO: ARMv8.2-SPE -- PMSCR_EL2 */
         /* TODO: ARMv8.4-Trace -- TRFCR_EL2 */
     };
@@ -7223,7 +7233,52 @@  static const ARMCPRegInfo mte_el0_cacheop_reginfo[] = {
     },
 };
 
-#endif
+static CPAccessResult access_scxtnum(CPUARMState *env, const ARMCPRegInfo *ri,
+                                     bool isread)
+{
+    uint64_t hcr = arm_hcr_el2_eff(env);
+    int el = arm_current_el(env);
+
+    if (el == 0 && !((hcr & HCR_E2H) && (hcr & HCR_TGE))) {
+        if (env->cp15.sctlr_el[1] & SCTLR_TSCXT) {
+            if (hcr & HCR_TGE) {
+                return CP_ACCESS_TRAP_EL2;
+            }
+            return CP_ACCESS_TRAP;
+        }
+    } else if (el < 2 && (env->cp15.sctlr_el[2] & SCTLR_TSCXT)) {
+        return CP_ACCESS_TRAP_EL2;
+    }
+    if (el < 2 && arm_is_el2_enabled(env) && !(hcr & HCR_ENSCXT)) {
+        return CP_ACCESS_TRAP_EL2;
+    }
+    if (el < 3
+        && arm_feature(env, ARM_FEATURE_EL3)
+        && !(env->cp15.scr_el3 & SCR_ENSCXT)) {
+        return CP_ACCESS_TRAP_EL3;
+    }
+    return CP_ACCESS_OK;
+}
+
+static const ARMCPRegInfo scxtnum_reginfo[] = {
+    { .name = "SCXTNUM_EL0", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 3, .crn = 13, .crm = 0, .opc2 = 7,
+      .access = PL0_RW, .accessfn = access_scxtnum,
+      .fieldoffset = offsetof(CPUARMState, scxtnum_el[0]) },
+    { .name = "SCXTNUM_EL1", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 0, .crn = 13, .crm = 0, .opc2 = 7,
+      .access = PL1_RW, .accessfn = access_scxtnum,
+      .fieldoffset = offsetof(CPUARMState, scxtnum_el[1]) },
+    { .name = "SCXTNUM_EL2", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 4, .crn = 13, .crm = 0, .opc2 = 7,
+      .access = PL2_RW, .accessfn = access_scxtnum,
+      .fieldoffset = offsetof(CPUARMState, scxtnum_el[2]) },
+    { .name = "SCXTNUM_EL3", .state = ARM_CP_STATE_AA64,
+      .opc0 = 3, .opc1 = 6, .crn = 13, .crm = 0, .opc2 = 7,
+      .access = PL3_RW,
+      .fieldoffset = offsetof(CPUARMState, scxtnum_el[3]) },
+};
+#endif /* TARGET_AARCH64 */
 
 static CPAccessResult access_predinv(CPUARMState *env, const ARMCPRegInfo *ri,
                                      bool isread)
@@ -8362,6 +8417,10 @@  void register_cp_regs_for_features(ARMCPU *cpu)
         define_arm_cp_regs(cpu, mte_tco_ro_reginfo);
         define_arm_cp_regs(cpu, mte_el0_cacheop_reginfo);
     }
+
+    if (cpu_isar_feature(aa64_scxtnum, cpu)) {
+        define_arm_cp_regs(cpu, scxtnum_reginfo);
+    }
 #endif
 
     if (cpu_isar_feature(any_predinv, cpu)) {