linux-kernel - [PATCH 2/3] KVM: SVM: Make MSR permission bitmap offsets read-only after init

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Message-ID: <20221110013003.1421895-3-seanjc@google.com>
Date:   Thu, 10 Nov 2022 01:30:02 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] KVM: SVM: Make MSR permission bitmap offsets read-only
 after init

Tag the pre-computed offsets into the MSR permission bitmaps as read-only
after init, and similarly tag add_msr_offset() and init_msrpm_offsets()
as __init.  The bitmaps themselves are dynamically configured, but the
offsets, i.e. the set of MSRs that can be passed through to the guest, is
static for a given instance of KVM.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.c | 6 +++---
 arch/x86/kvm/svm/svm.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 527f18d8cc44..e96c808fa8d3 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -65,7 +65,7 @@ MODULE_DEVICE_TABLE(x86cpu, svm_cpu_id);
 
 static bool erratum_383_found __read_mostly;
 
-u32 msrpm_offsets[MSRPM_OFFSETS] __read_mostly;
+u32 msrpm_offsets[MSRPM_OFFSETS] __ro_after_init;
 
 /*
  * Set osvw_len to higher value when updated Revision Guides
@@ -860,7 +860,7 @@ static void svm_msr_filter_changed(struct kvm_vcpu *vcpu)
 	}
 }
 
-static void add_msr_offset(u32 offset)
+__init static void add_msr_offset(u32 offset)
 {
 	int i;
 
@@ -887,7 +887,7 @@ static void add_msr_offset(u32 offset)
 	BUG();
 }
 
-static void init_msrpm_offsets(void)
+__init static void init_msrpm_offsets(void)
 {
 	int i;
 
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 199a2ecef1ce..ca348e016729 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -31,7 +31,7 @@
 
 #define MAX_DIRECT_ACCESS_MSRS	46
 #define MSRPM_OFFSETS	32
-extern u32 msrpm_offsets[MSRPM_OFFSETS] __read_mostly;
+extern u32 msrpm_offsets[MSRPM_OFFSETS] __ro_after_init;
 extern bool npt_enabled;
 extern int vgif;
 extern bool intercept_smi;
-- 
2.38.1.431.g37b22c650d-goog