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Date: Mon, 10 May 2021 11:28:54 +0300
From: Maxim Levitsky <mlevitsk@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>,
Reiji Watanabe <reijiw@...gle.com>
Subject: Re: [PATCH 13/15] KVM: x86: Move uret MSR slot management to common
x86
On Tue, 2021-05-04 at 10:17 -0700, Sean Christopherson wrote:
> Now that SVM and VMX both probe MSRs before "defining" user return slots
> for them, consolidate the code for probe+define into common x86 and
> eliminate the odd behavior of having the vendor code define the slot for
> a given MSR.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
> arch/x86/include/asm/kvm_host.h | 3 +--
> arch/x86/kvm/svm/svm.c | 5 +----
> arch/x86/kvm/vmx/vmx.c | 19 ++++---------------
> arch/x86/kvm/x86.c | 19 +++++++++++--------
> 4 files changed, 17 insertions(+), 29 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 10663610f105..a4b912f7e427 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1778,9 +1778,8 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low,
> unsigned long ipi_bitmap_high, u32 min,
> unsigned long icr, int op_64_bit);
>
> -void kvm_define_user_return_msr(unsigned index, u32 msr);
> +int kvm_add_user_return_msr(u32 msr);
> int kvm_find_user_return_msr(u32 msr);
> -int kvm_probe_user_return_msr(u32 msr);
> int kvm_set_user_return_msr(unsigned index, u64 val, u64 mask);
>
> u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc);
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 231b9650d864..de921935e8de 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -959,10 +959,7 @@ static __init int svm_hardware_setup(void)
> kvm_tsc_scaling_ratio_frac_bits = 32;
> }
>
> - if (!kvm_probe_user_return_msr(MSR_TSC_AUX)) {
> - tsc_aux_uret_slot = 0;
> - kvm_define_user_return_msr(tsc_aux_uret_slot, MSR_TSC_AUX);
> - }
> + tsc_aux_uret_slot = kvm_add_user_return_msr(MSR_TSC_AUX);
>
> /* Check for pause filtering support */
> if (!boot_cpu_has(X86_FEATURE_PAUSEFILTER)) {
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 7a53568b34fc..26f82f302391 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -454,9 +454,6 @@ static inline void vmx_segment_cache_clear(struct vcpu_vmx *vmx)
>
> static unsigned long host_idt_base;
>
> -/* Number of user return MSRs that are actually supported in hardware. */
> -static int vmx_nr_uret_msrs;
> -
> #if IS_ENABLED(CONFIG_HYPERV)
> static bool __read_mostly enlightened_vmcs = true;
> module_param(enlightened_vmcs, bool, 0444);
> @@ -1218,7 +1215,7 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
> */
> if (!vmx->guest_uret_msrs_loaded) {
> vmx->guest_uret_msrs_loaded = true;
> - for (i = 0; i < vmx_nr_uret_msrs; ++i) {
> + for (i = 0; i < kvm_nr_uret_msrs; ++i) {
> if (!vmx->guest_uret_msrs[i].load_into_hardware)
> continue;
>
> @@ -6921,7 +6918,7 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu)
> goto free_vpid;
> }
>
> - for (i = 0; i < vmx_nr_uret_msrs; ++i) {
> + for (i = 0; i < kvm_nr_uret_msrs; ++i) {
> vmx->guest_uret_msrs[i].data = 0;
> vmx->guest_uret_msrs[i].mask = -1ull;
> }
> @@ -7810,20 +7807,12 @@ static __init void vmx_setup_user_return_msrs(void)
> MSR_EFER, MSR_TSC_AUX, MSR_STAR,
> MSR_IA32_TSX_CTRL,
> };
> - u32 msr;
> int i;
>
> BUILD_BUG_ON(ARRAY_SIZE(vmx_uret_msrs_list) != MAX_NR_USER_RETURN_MSRS);
>
> - for (i = 0; i < ARRAY_SIZE(vmx_uret_msrs_list); ++i) {
> - msr = vmx_uret_msrs_list[i];
> -
> - if (kvm_probe_user_return_msr(msr))
> - continue;
> -
> - kvm_define_user_return_msr(vmx_nr_uret_msrs, msr);
> - vmx_nr_uret_msrs++;
> - }
> + for (i = 0; i < ARRAY_SIZE(vmx_uret_msrs_list); ++i)
> + kvm_add_user_return_msr(vmx_uret_msrs_list[i]);
> }
>
> static __init int hardware_setup(void)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 2fd46e917666..adca491d3b4b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -336,7 +336,7 @@ static void kvm_on_user_return(struct user_return_notifier *urn)
> }
> }
>
> -int kvm_probe_user_return_msr(u32 msr)
> +static int kvm_probe_user_return_msr(u32 msr)
> {
> u64 val;
> int ret;
> @@ -350,16 +350,18 @@ int kvm_probe_user_return_msr(u32 msr)
> preempt_enable();
> return ret;
> }
> -EXPORT_SYMBOL_GPL(kvm_probe_user_return_msr);
>
> -void kvm_define_user_return_msr(unsigned slot, u32 msr)
> +int kvm_add_user_return_msr(u32 msr)
> {
> - BUG_ON(slot >= KVM_MAX_NR_USER_RETURN_MSRS);
> - kvm_uret_msrs_list[slot] = msr;
> - if (slot >= kvm_nr_uret_msrs)
> - kvm_nr_uret_msrs = slot + 1;
> + BUG_ON(kvm_nr_uret_msrs >= KVM_MAX_NR_USER_RETURN_MSRS);
> +
> + if (kvm_probe_user_return_msr(msr))
> + return -1;
> +
> + kvm_uret_msrs_list[kvm_nr_uret_msrs] = msr;
> + return kvm_nr_uret_msrs++;
> }
> -EXPORT_SYMBOL_GPL(kvm_define_user_return_msr);
> +EXPORT_SYMBOL_GPL(kvm_add_user_return_msr);
>
> int kvm_find_user_return_msr(u32 msr)
> {
> @@ -8169,6 +8171,7 @@ int kvm_arch_init(void *opaque)
> printk(KERN_ERR "kvm: failed to allocate percpu kvm_user_return_msrs\n");
> goto out_free_x86_emulator_cache;
> }
> + kvm_nr_uret_msrs = 0;
>
> r = kvm_mmu_module_init();
> if (r)
Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
Best regards,
Maxim Levitsky
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