KVM: selftests: Add support for DIV and IDIV in the fastops test

Extend the fastops test coverage to DIV and IDIV, specifically to provide
coverage for #DE (divide error) exceptions, as #DE is the only exception
that can occur in KVM's fastops path, i.e. that requires exception fixup.

Link: https://lore.kernel.org/r/20250909202835.333554-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/x86/fastops_test.c b/tools/testing/selftests/kvm/x86/fastops_test.c
index 26a381c8303ac2ff4c438ac793fd697418c4aa6d..8926cfe0e2099950e9525fd72cbbc4219ead9661 100644 (file)
--- a/tools/testing/selftests/kvm/x86/fastops_test.c
+++ b/tools/testing/selftests/kvm/x86/fastops_test.c
@@ -92,6 +92,42 @@
                        ex_flags, insn, shift, (uint64_t)input, flags);                 \
 })
 
+#define guest_execute_fastop_div(__KVM_ASM_SAFE, insn, __a, __d, __rm, __flags)                \
+({                                                                                     \
+       uint64_t ign_error_code;                                                        \
+       uint8_t vector;                                                                 \
+                                                                                       \
+       __asm__ __volatile__(fastop(__KVM_ASM_SAFE(insn " %[denom]"))                   \
+                            : "+a"(__a), "+d"(__d), flags_constraint(__flags),         \
+                              KVM_ASM_SAFE_OUTPUTS(vector, ign_error_code)             \
+                            : [denom]"rm"(__rm), bt_constraint(__rm)                   \
+                            : "cc", "memory", KVM_ASM_SAFE_CLOBBERS);                  \
+       vector;                                                                         \
+})
+
+#define guest_test_fastop_div(insn, type_t, __val1, __val2)                            \
+({                                                                                     \
+       type_t _a = __val1, _d = __val1, rm = __val2;                                   \
+       type_t a = _a, d = _d, ex_a = _a, ex_d = _d;                                    \
+       uint64_t flags, ex_flags;                                                       \
+       uint8_t v, ex_v;                                                                \
+                                                                                       \
+       ex_v = guest_execute_fastop_div(KVM_ASM_SAFE, insn, ex_a, ex_d, rm, ex_flags);  \
+       v = guest_execute_fastop_div(KVM_ASM_SAFE_FEP, insn, a, d, rm, flags);          \
+                                                                                       \
+       GUEST_ASSERT_EQ(v, ex_v);                                                       \
+       __GUEST_ASSERT(v == ex_v,                                                       \
+                      "Wanted vector 0x%x for '%s 0x%lx:0x%lx/0x%lx', got 0x%x",       \
+                      ex_v, insn, (uint64_t)_a, (uint64_t)_d, (uint64_t)rm, v);        \
+       __GUEST_ASSERT(a == ex_a && d == ex_d,                                          \
+                      "Wanted 0x%lx:0x%lx for '%s 0x%lx:0x%lx/0x%lx', got 0x%lx:0x%lx",\
+                      (uint64_t)ex_a, (uint64_t)ex_d, insn, (uint64_t)_a,              \
+                      (uint64_t)_d, (uint64_t)rm, (uint64_t)a, (uint64_t)d);           \
+       __GUEST_ASSERT(v || ex_v || (flags == ex_flags),                                \
+                       "Wanted flags 0x%lx for '%s  0x%lx:0x%lx/0x%lx', got 0x%lx",    \
+                       ex_flags, insn, (uint64_t)_a, (uint64_t)_d, (uint64_t)rm, flags);\
+})
+
 static const uint64_t vals[] = {
        0,
        1,
@@ -141,6 +177,8 @@ if (sizeof(type_t) != 1) {                                                  \
                        guest_test_fastop_cl("sar" suffix, type_t, vals[i], vals[j]);   \
                        guest_test_fastop_cl("shl" suffix, type_t, vals[i], vals[j]);   \
                        guest_test_fastop_cl("shr" suffix, type_t, vals[i], vals[j]);   \
+                                                                                       \
+                       guest_test_fastop_div("div" suffix, type_t, vals[i], vals[j]);  \
                }                                                                       \
        }                                                                               \
 } while (0)