linux-kernel - [PATCH v6 15/21] kvm: x86: Add XCR0 support for Intel AMX

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Message-Id: <20220107185512.25321-16-pbonzini@redhat.com>
Date:   Fri,  7 Jan 2022 13:55:06 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     guang.zeng@...el.com, jing2.liu@...el.com, kevin.tian@...el.com,
        seanjc@...gle.com, tglx@...utronix.de, wei.w.wang@...el.com,
        yang.zhong@...el.com
Subject: [PATCH v6 15/21] kvm: x86: Add XCR0 support for Intel AMX

From: Jing Liu <jing2.liu@...el.com>

Two XCR0 bits are defined for AMX to support XSAVE mechanism. Bit 17
is for tilecfg and bit 18 is for tiledata.

The value of XCR0[17:18] is always either 00b or 11b. Also, SDM
recommends that only 64-bit operating systems enable Intel AMX by
setting XCR0[18:17]. 32-bit host kernel never sets the tile bits in
vcpu->arch.guest_supported_xcr0.

Signed-off-by: Jing Liu <jing2.liu@...el.com>
Signed-off-by: Kevin Tian <kevin.tian@...el.com>
Signed-off-by: Yang Zhong <yang.zhong@...el.com>
Message-Id: <20220105123532.12586-16-yang.zhong@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/x86.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2475b64cb762..993eee6451ea 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -211,7 +211,7 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
 #define KVM_SUPPORTED_XCR0     (XFEATURE_MASK_FP | XFEATURE_MASK_SSE \
 				| XFEATURE_MASK_YMM | XFEATURE_MASK_BNDREGS \
 				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
-				| XFEATURE_MASK_PKRU)
+				| XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)
 
 u64 __read_mostly host_efer;
 EXPORT_SYMBOL_GPL(host_efer);
@@ -1010,6 +1010,11 @@ static int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
 		if ((xcr0 & XFEATURE_MASK_AVX512) != XFEATURE_MASK_AVX512)
 			return 1;
 	}
+
+	if ((xcr0 & XFEATURE_MASK_XTILE) &&
+	    ((xcr0 & XFEATURE_MASK_XTILE) != XFEATURE_MASK_XTILE))
+		return 1;
+
 	vcpu->arch.xcr0 = xcr0;
 
 	if ((xcr0 ^ old_xcr0) & XFEATURE_MASK_EXTEND)
-- 
2.31.1