linux-kernel - [PATCH v2 7/7] KVM: selftests: x86: Repeat the checking of xheader when IA32_XFD[XTILEDATA] is set in amx

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Message-ID: <20230214184606.510551-8-mizhang@google.com>
Date:   Tue, 14 Feb 2023 18:46:06 +0000
From:   Mingwei Zhang <mizhang@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mingwei Zhang <mizhang@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Venkatesh Srinivas <venkateshs@...gle.com>,
        Aaron Lewis <aaronlewis@...gle.com>,
        "Chang S. Bae" <chang.seok.bae@...el.com>
Subject: [PATCH v2 7/7] KVM: selftests: x86: Repeat the checking of xheader
 when IA32_XFD[XTILEDATA] is set in amx_test

Repeat the checking of AMX component in xheader after XSAVEC when
IA32_XFD[XTILEDATA] 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 the corresponding bits are set XCR0.

Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
---
 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 0e4c65f9e2f2..d991a473dc11 100644
--- a/tools/testing/selftests/kvm/x86_64/amx_test.c
+++ b/tools/testing/selftests/kvm/x86_64/amx_test.c
@@ -201,6 +201,16 @@ static void __attribute__((__flatten__)) guest_code(struct tile_config *amx_cfg,
 
 	/* xfd=0x40000, disable amx tiledata */
 	wrmsr(MSR_IA32_XFD, XFEATURE_MASK_XTILEDATA);
+
+	/*
+	 * XTILEDATA is cleared in xstate_bv but set in xcomp_bv, this property
+	 * remains the same even when amx tiledata is disabled by IA32_XFD.
+	 */
+	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));
+
 	GUEST_SYNC(6);
 	GUEST_ASSERT(rdmsr(MSR_IA32_XFD) == XFEATURE_MASK_XTILEDATA);
 	set_tilecfg(amx_cfg);
-- 
2.39.1.581.gbfd45094c4-goog