[PATCH 4/4] KVM: selftests: x86: Repeat the checking of xheader when IA32_XFD[18] is set in amx_test

[Mingwei Zhang]

Repeat the checking of AMX component in xheader after xsavec when
IA32_XFD[18] is set. This check calibrates the functionality scope of
IA32_XFD: it does not intercept the XSAVE state management. Regardless of
the values in IA32_XFD, AMX component state will still be managed by XSAVE*
and XRSTOR* as long as XCR[18:17] are set.

Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
---
 tools/testing/selftests/kvm/x86_64/amx_test.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86_64/amx_test.c b/tools/testing/selftests/kvm/x86_64/amx_test.c
index 18203e399e9d..9a80a59b64e6 100644
--- a/tools/testing/selftests/kvm/x86_64/amx_test.c
+++ b/tools/testing/selftests/kvm/x86_64/amx_test.c
@@ -235,6 +235,16 @@ static void __attribute__((__flatten__)) guest_code(struct tile_config *amx_cfg,
 
 	/* xfd=0x40000, disable amx tiledata */
 	wrmsr(MSR_IA32_XFD, XFEATURE_MASK_XTILEDATA);
+
+	/*
+	 * Bit 18 is cleared in XSTATE_BV but set in XCOMP_BV, this property
+	 * remains the same even when IA32_XFD disables amx tiledata.
+	 */
+	set_xstatebv(xsave_data, XFEATURE_MASK_XTILEDATA);
+	__xsavec(xsave_data, XFEATURE_MASK_XTILEDATA);
+	GUEST_ASSERT((get_xstatebv(xsave_data) & XFEATURE_MASK_XTILEDATA) == 0);
+	GUEST_ASSERT((get_xcompbv(xsave_data) & XFEATURE_MASK_XTILEDATA) == XFEATURE_MASK_XTILEDATA);
+
 	GUEST_SYNC(6);
 	GUEST_ASSERT(rdmsr(MSR_IA32_XFD) == XFEATURE_MASK_XTILEDATA);
 	set_tilecfg(amx_cfg);
-- 
2.39.0.314.g84b9a713c41-goog