From: Richard Henderson <richard.henderson@linaro.org>

If translation is enabled, and the PTE memory type is Device,
enable checking alignment via TLB_CHECK_ALIGNMENT.  While the
check is done later than it should be per the ARM, it's better
than not performing the check at all.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240301204110.656742-7-richard.henderson@linaro.org
[PMM: tweaks to comment text]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/ptw.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/target/arm/ptw.c b/target/arm/ptw.c
index ba1a27ca2b5..31ae43f60ed 100644
--- a/target/arm/ptw.c
+++ b/target/arm/ptw.c
@@ -471,6 +471,16 @@ static bool granule_protection_check(CPUARMState *env, uint64_t paddress,
     return false;
 }
 
+static bool S1_attrs_are_device(uint8_t attrs)
+{
+    /*
+     * This slightly under-decodes the MAIR_ELx field:
+     * 0b0000dd01 is Device with FEAT_XS, otherwise UNPREDICTABLE;
+     * 0b0000dd1x is UNPREDICTABLE.
+     */
+    return (attrs & 0xf0) == 0;
+}
+
 static bool S2_attrs_are_device(uint64_t hcr, uint8_t attrs)
 {
     /*
@@ -1684,6 +1694,7 @@ static bool get_phys_addr_lpae(CPUARMState *env, S1Translate *ptw,
     bool aarch64 = arm_el_is_aa64(env, el);
     uint64_t descriptor, new_descriptor;
     ARMSecuritySpace out_space;
+    bool device;
 
     /* TODO: This code does not support shareability levels. */
     if (aarch64) {
@@ -2106,6 +2117,12 @@ static bool get_phys_addr_lpae(CPUARMState *env, S1Translate *ptw,
     if (regime_is_stage2(mmu_idx)) {
         result->cacheattrs.is_s2_format = true;
         result->cacheattrs.attrs = extract32(attrs, 2, 4);
+        /*
+         * Security state does not really affect HCR_EL2.FWB;
+         * we only need to filter FWB for aa32 or other FEAT.
+         */
+        device = S2_attrs_are_device(arm_hcr_el2_eff(env),
+                                     result->cacheattrs.attrs);
     } else {
         /* Index into MAIR registers for cache attributes */
         uint8_t attrindx = extract32(attrs, 2, 3);
@@ -2118,6 +2135,28 @@ static bool get_phys_addr_lpae(CPUARMState *env, S1Translate *ptw,
         if (aarch64 && cpu_isar_feature(aa64_bti, cpu)) {
             result->f.extra.arm.guarded = extract64(attrs, 50, 1); /* GP */
         }
+        device = S1_attrs_are_device(result->cacheattrs.attrs);
+    }
+
+    /*
+     * Enable alignment checks on Device memory.
+     *
+     * Per R_XCHFJ, this check is mis-ordered. The correct ordering
+     * for alignment, permission, and stage 2 faults should be:
+     *    - Alignment fault caused by the memory type
+     *    - Permission fault
+     *    - A stage 2 fault on the memory access
+     * but due to the way the TCG softmmu TLB operates, we will have
+     * implicitly done the permission check and the stage2 lookup in
+     * finding the TLB entry, so the alignment check cannot be done sooner.
+     *
+     * In v7, for a CPU without the Virtualization Extensions this
+     * access is UNPREDICTABLE; we choose to make it take the alignment
+     * fault as is required for a v7VE CPU. (QEMU doesn't emulate any
+     * CPUs with ARM_FEATURE_LPAE but not ARM_FEATURE_V7VE anyway.)
+     */
+    if (device) {
+        result->f.tlb_fill_flags |= TLB_CHECK_ALIGNED;
     }
 
     /*
-- 
2.34.1