Commit 9bf5da1c authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: selftests: Add coverage for 'b' (byte) sized fastops emulation 

Extend the fastops test to cover instructions that operate on 8-bit data.
Support for 8-bit instructions was omitted from the original commit purely
due to complications with BT not having a r/m8 variant.  To keep the
RFLAGS.CF behavior deterministic and not heavily biased to '0' or '1',
continue using BT, but cast and load the to-be-tested value into a
dedicated 32-bit constraint.

Supporting 8-bit operations will allow using guest_test_fastops() as-is to
provide full coverage for DIV and IDIV.  For divide operations, covering
all operand sizes _is_ interesting, because KVM needs provide exception
fixup for each size (failure to handle a #DE could panic the host).

Link: https://lore.kernel.org/all/aIF7ZhWZxlkcpm4y@google.com
Link: https://lore.kernel.org/r/20250909202835.333554-3-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 7b39b6c7

tools/testing/selftests/kvm/x86/fastops_test.c

+13 −7
Original line number Diff line number Diff line
@@ -10,12 +10,13 @@ 
 */

#define guest_execute_fastop_1(FEP, insn, __val, __flags)				\

({											\

	__asm__ __volatile__("bt $0, %[val]\n\t"					\

	__asm__ __volatile__("bt $0, %[ro_val]\n\t"					\

			     FEP insn " %[val]\n\t"					\

			     "pushfq\n\t"						\

			     "pop %[flags]\n\t"						\

			     : [val]"+r"(__val), [flags]"=r"(__flags)			\

			     : : "cc", "memory");					\

			     : [ro_val]"rm"((uint32_t)__val)				\

			     : "cc", "memory");						\

})



#define guest_test_fastop_1(insn, type_t, __val)					\
@@ -36,12 +37,13 @@ 


#define guest_execute_fastop_2(FEP, insn, __input, __output, __flags)			\

({											\

	__asm__ __volatile__("bt $0, %[output]\n\t"					\

	__asm__ __volatile__("bt $0, %[ro_val]\n\t"					\

			     FEP insn " %[input], %[output]\n\t"			\

			     "pushfq\n\t"						\

			     "pop %[flags]\n\t"						\

			     : [output]"+r"(__output), [flags]"=r"(__flags)		\

			     : [input]"r"(__input) : "cc", "memory");			\

			     : [input]"r"(__input), [ro_val]"rm"((uint32_t)__output)	\

			     : "cc", "memory");						\

})



#define guest_test_fastop_2(insn, type_t, __val1, __val2)				\
@@ -63,12 +65,13 @@ 


#define guest_execute_fastop_cl(FEP, insn, __shift, __output, __flags)			\

({											\

	__asm__ __volatile__("bt $0, %[output]\n\t"					\

	__asm__ __volatile__("bt $0, %[ro_val]\n\t"					\

			     FEP insn " %%cl, %[output]\n\t"				\

			     "pushfq\n\t"						\

			     "pop %[flags]\n\t"						\

			     : [output]"+r"(__output), [flags]"=r"(__flags)		\

			     : "c"(__shift) : "cc", "memory");				\

			     : "c"(__shift), [ro_val]"rm"((uint32_t)__output)		\

			     : "cc", "memory");						\

})



#define guest_test_fastop_cl(insn, type_t, __val1, __val2)				\
@@ -115,14 +118,16 @@ do { \ 
			guest_test_fastop_2("add" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("adc" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("and" suffix, type_t, vals[i], vals[j]);	\

if (sizeof(type_t) != 1) {							\

			guest_test_fastop_2("bsf" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("bsr" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("bt" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("btc" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("btr" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("bts" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("cmp" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("imul" suffix, type_t, vals[i], vals[j]);	\

}											\

			guest_test_fastop_2("cmp" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("or" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("sbb" suffix, type_t, vals[i], vals[j]);	\

			guest_test_fastop_2("sub" suffix, type_t, vals[i], vals[j]);	\
@@ -142,6 +147,7 @@ do { \ 


static void guest_code(void)

{

	guest_test_fastops(uint8_t, "b");

	guest_test_fastops(uint16_t, "w");

	guest_test_fastops(uint32_t, "l");

	guest_test_fastops(uint64_t, "q");