linux-kernel - [PATCH] KVM: x86/cpuid: Exclude unpermitted xfeatures sizes at KVM_GET_SUPPORTED

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Date:   Mon, 24 Jan 2022 16:02:51 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Tian Kevin <kevin.tian@...el.com>,
        Jim Mattson <jmattson@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: x86/cpuid: Exclude unpermitted xfeatures sizes at KVM_GET_SUPPORTED_CPUID

From: Like Xu <likexu@...cent.com>

With the help of xstate_get_guest_group_perm(), KVM can exclude unpermitted
xfeatures in cpuid.0xd.0.eax, in which case the corresponding xfeatures
sizes should also be matched to the permitted xfeatures.

Fixing this inconsistency by introducing a local variable with the same
name also helps to fix cpuid.0xd.1.ebx and later leaf-by-leaf queries.

Fixes: 445ecdf79be0 ("kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED_CPUID")
Signed-off-by: Like Xu <likexu@...cent.com>
---
 arch/x86/kvm/cpuid.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 3902c28fb6cb..3dcd58a138a9 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -887,12 +887,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		}
 		break;
 	case 0xd: {
-		u64 guest_perm = xstate_get_guest_group_perm();
+		u64 supported_xcr0 = supported_xcr0 & xstate_get_guest_group_perm();
 
-		entry->eax &= supported_xcr0 & guest_perm;
+		entry->eax &= supported_xcr0;
 		entry->ebx = xstate_required_size(supported_xcr0, false);
 		entry->ecx = entry->ebx;
-		entry->edx &= (supported_xcr0 & guest_perm) >> 32;
+		entry->edx &= supported_xcr0 >> 32;
 		if (!supported_xcr0)
 			break;
 
-- 
2.33.1