After tilerelease instruction, AMX tiles are in INIT state. According to Intel SDM vol 1. 13.10: "If RFBM[i] = 1, XSTATE_BV[i] is set to the value of XINUSE[i].", XSTATE_BV[18] should be cleared after xsavec.
On the other hand, according to Intel SDM vol 1. 13.4.3: "If XCOMP_BV[i] = 1, state component i is located at a byte offset locationI from the base address of the XSAVE area". Since at the time of xsavec, XCR0[18] is set indicating AMX tile data component is still enabled, xcomp_bv[18] should be set.
Complete the checks by adding the assert to xcomp_bv[18] after xsavec.
Signed-off-by: Mingwei Zhang mizhang@google.com --- tools/testing/selftests/kvm/x86_64/amx_test.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/tools/testing/selftests/kvm/x86_64/amx_test.c b/tools/testing/selftests/kvm/x86_64/amx_test.c index 16c857c1052e..ba8c0afdbac8 100644 --- a/tools/testing/selftests/kvm/x86_64/amx_test.c +++ b/tools/testing/selftests/kvm/x86_64/amx_test.c @@ -197,6 +197,7 @@ static void __attribute__((__flatten__)) guest_code(struct tile_config *amx_cfg, xstate->header.xstate_bv = XFEATURE_MASK_XTILEDATA; __xsavec(xstate, XFEATURE_MASK_XTILEDATA); GUEST_ASSERT(!(xstate->header.xstate_bv & XFEATURE_MASK_XTILEDATA)); + GUEST_ASSERT((xstate->header.xcomp_bv & XFEATURE_MASK_XTILEDATA));
/* xfd=0x40000, disable amx tiledata */ wrmsr(MSR_IA32_XFD, XFEATURE_MASK_XTILEDATA);