target/arm: Handle AArch32 CP15 trapping via HSTR_EL2

HSTR_EL2 offers a way to trap ranges of CP15 system register
accesses to EL2, and it looks like this register is completely
ignored by QEMU.

To avoid adding extra .accessfn filters all over the place (which
would have a direct performance impact), let's add a new TB flag
that gets set whenever HSTR_EL2 is non-zero and that QEMU translates
a context where this trap has a chance to apply, and only generate
the extra access check if the hypervisor is actively using this feature.

Tested with a hand-crafted KVM guest accessing CBAR.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20191201122018.25808-5-maz@kernel.org
[PMM: use is_a64(); fix comment syntax]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 83a809d4bac45b0cdf7610decf43fb5151e7a599..cebb3511a518756de1d73a463604359b168817c1 100644 (file)
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -3215,6 +3215,8 @@ FIELD(TBFLAG_A32, NS, 6, 1)
 FIELD(TBFLAG_A32, VFPEN, 7, 1)          /* Partially cached, minus FPEXC. */
 FIELD(TBFLAG_A32, CONDEXEC, 8, 8)       /* Not cached. */
 FIELD(TBFLAG_A32, SCTLR_B, 16, 1)
+FIELD(TBFLAG_A32, HSTR_ACTIVE, 17, 1)
+
 /* For M profile only, set if FPCCR.LSPACT is set */
 FIELD(TBFLAG_A32, LSPACT, 18, 1)        /* Not cached. */
 /* For M profile only, set if we must create a new FP context */

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 93ecab27c0c1b4a9e5c20cf9732a1432063f6a1f..0ba08d550aa111073104355c9e2ae9d6223e85a4 100644 (file)
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -11283,6 +11283,12 @@ static uint32_t rebuild_hflags_a32(CPUARMState *env, int fp_el,
     if (arm_el_is_aa64(env, 1)) {
         flags = FIELD_DP32(flags, TBFLAG_A32, VFPEN, 1);
     }
+
+    if (arm_current_el(env) < 2 && env->cp15.hstr_el2 &&
+        (arm_hcr_el2_eff(env) & (HCR_E2H | HCR_TGE)) != (HCR_E2H | HCR_TGE)) {
+        flags = FIELD_DP32(flags, TBFLAG_A32, HSTR_ACTIVE, 1);
+    }
+
     return rebuild_hflags_common_32(env, fp_el, mmu_idx, flags);
 }
 

diff --git a/target/arm/op_helper.c b/target/arm/op_helper.c
index b529d6c1bf7eea82cc2c83ee37b1d45aa64fc546..e5a346cb87a30140d085361180422edd01d38d10 100644 (file)
--- a/target/arm/op_helper.c
+++ b/target/arm/op_helper.c
@@ -603,6 +603,27 @@ void HELPER(access_check_cp_reg)(CPUARMState *env, void *rip, uint32_t syndrome,
         raise_exception(env, EXCP_UDEF, syndrome, exception_target_el(env));
     }
 
+    /*
+     * Check for an EL2 trap due to HSTR_EL2. We expect EL0 accesses
+     * to sysregs non accessible at EL0 to have UNDEF-ed already.
+     */
+    if (!is_a64(env) && arm_current_el(env) < 2 && ri->cp == 15 &&
+        (arm_hcr_el2_eff(env) & (HCR_E2H | HCR_TGE)) != (HCR_E2H | HCR_TGE)) {
+        uint32_t mask = 1 << ri->crn;
+
+        if (ri->type & ARM_CP_64BIT) {
+            mask = 1 << ri->crm;
+        }
+
+        /* T4 and T14 are RES0 */
+        mask &= ~((1 << 4) | (1 << 14));
+
+        if (env->cp15.hstr_el2 & mask) {
+            target_el = 2;
+            goto exept;
+        }
+    }
+
     if (!ri->accessfn) {
         return;
     }
@@ -652,6 +673,7 @@ void HELPER(access_check_cp_reg)(CPUARMState *env, void *rip, uint32_t syndrome,
         g_assert_not_reached();
     }
 
+exept:
     raise_exception(env, EXCP_UDEF, syndrome, target_el);
 }
 

diff --git a/target/arm/translate.c b/target/arm/translate.c
index 4d5d4bd8886c138196cec746f0e78fcde1aaec28..f162be8434f1e68642db666a9e92040f1bf47819 100644 (file)
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -6897,7 +6897,7 @@ static int disas_coproc_insn(DisasContext *s, uint32_t insn)
             return 1;
         }
 
-        if (ri->accessfn ||
+        if (s->hstr_active || ri->accessfn ||
             (arm_dc_feature(s, ARM_FEATURE_XSCALE) && cpnum < 14)) {
             /* Emit code to perform further access permissions checks at
              * runtime; this may result in an exception.
@@ -10843,6 +10843,7 @@ static void arm_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
                                !arm_el_is_aa64(env, 3);
     dc->thumb = FIELD_EX32(tb_flags, TBFLAG_A32, THUMB);
     dc->sctlr_b = FIELD_EX32(tb_flags, TBFLAG_A32, SCTLR_B);
+    dc->hstr_active = FIELD_EX32(tb_flags, TBFLAG_A32, HSTR_ACTIVE);
     dc->be_data = FIELD_EX32(tb_flags, TBFLAG_ANY, BE_DATA) ? MO_BE : MO_LE;
     condexec = FIELD_EX32(tb_flags, TBFLAG_A32, CONDEXEC);
     dc->condexec_mask = (condexec & 0xf) << 1;

diff --git a/target/arm/translate.h b/target/arm/translate.h
index dd24f91f265e72cb6e978ed310d48138ebdaf4f4..b837b7fcbf10262d914e2282755a68e4e30f8b56 100644 (file)
--- a/target/arm/translate.h
+++ b/target/arm/translate.h
@@ -77,6 +77,8 @@ typedef struct DisasContext {
     bool pauth_active;
     /* True with v8.5-BTI and SCTLR_ELx.BT* set.  */
     bool bt;
+    /* True if any CP15 access is trapped by HSTR_EL2 */
+    bool hstr_active;
     /*
      * >= 0, a copy of PSTATE.BTYPE, which will be 0 without v8.5-BTI.
      *  < 0, set by the current instruction.