KVM: x86: Restrict get_mt_mask() to a u8, use KVM_X86_OP_OPTIONAL_RET0

Restrict get_mt_mask() to a u8 and reintroduce using a RET0 static_call
for the SVM implementation.  EPT stores the memtype information in the
lower 8 bits (bits 6:3 to be precise), and even returns a shifted u8
without an explicit cast to a larger type; there's no need to return a
full u64.

Note, RET0 doesn't play nice with a u64 return on 32-bit kernels, see
commit 24449ae33b30 ("KVM: x86: do not use KVM_X86_OP_OPTIONAL_RET0 for
get_mt_mask").

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220714153707.3239119-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 6f2f1affbb7828e33a0bb76675420856f30ebd3d..51f7770715848968da6ece4c5cb95ec18f089c10 100644 (file)
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -88,7 +88,7 @@ KVM_X86_OP(deliver_interrupt)
 KVM_X86_OP_OPTIONAL(sync_pir_to_irr)
 KVM_X86_OP_OPTIONAL_RET0(set_tss_addr)
 KVM_X86_OP_OPTIONAL_RET0(set_identity_map_addr)
-KVM_X86_OP(get_mt_mask)
+KVM_X86_OP_OPTIONAL_RET0(get_mt_mask)
 KVM_X86_OP(load_mmu_pgd)
 KVM_X86_OP(has_wbinvd_exit)
 KVM_X86_OP(get_l2_tsc_offset)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d4ece7bf2124f2ee33baec17a6b767a868a5ab4e..e8281d64a4315a0643ec22ca6df8c4f51e6c32cd 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1545,7 +1545,7 @@ struct kvm_x86_ops {
        int (*sync_pir_to_irr)(struct kvm_vcpu *vcpu);
        int (*set_tss_addr)(struct kvm *kvm, unsigned int addr);
        int (*set_identity_map_addr)(struct kvm *kvm, u64 ident_addr);
-       u64 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
+       u8 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
 
        void (*load_mmu_pgd)(struct kvm_vcpu *vcpu, hpa_t root_hpa,
                             int root_level);

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 84414eafcd0dd425be19ff77ae70956124ec0613..ba81a7e58f751dba5feae948ceb015a9a7fdd5c8 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4159,11 +4159,6 @@ static bool svm_has_emulated_msr(struct kvm *kvm, u32 index)
        return true;
 }
 
-static u64 svm_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
-{
-       return 0;
-}
-
 static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
@@ -4815,7 +4810,6 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
        .check_apicv_inhibit_reasons = avic_check_apicv_inhibit_reasons,
        .apicv_post_state_restore = avic_apicv_post_state_restore,
 
-       .get_mt_mask = svm_get_mt_mask,
        .get_exit_info = svm_get_exit_info,
 
        .vcpu_after_set_cpuid = svm_vcpu_after_set_cpuid,

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e6ab2c2c4d3bd5484d877c1e177c653e3b653d51..b0cc911a8f6f803795c4a72e177ed90427baed19 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7354,7 +7354,7 @@ static int __init vmx_check_processor_compat(void)
        return 0;
 }
 
-static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
+static u8 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
 {
        u8 cache;