linux-kernel - Re: [PATCH 7/7] KVM: TDX: Add TSX_CTRL msr into uret

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Message-ID: <Zz/6NBmZIcRUFvLQ@intel.com>
Date: Fri, 22 Nov 2024 11:27:48 +0800
From: Chao Gao <chao.gao@...el.com>
To: Adrian Hunter <adrian.hunter@...el.com>
CC: <pbonzini@...hat.com>, <seanjc@...gle.com>, <kvm@...r.kernel.org>,
	<dave.hansen@...ux.intel.com>, <rick.p.edgecombe@...el.com>,
	<kai.huang@...el.com>, <reinette.chatre@...el.com>, <xiaoyao.li@...el.com>,
	<tony.lindgren@...ux.intel.com>, <binbin.wu@...ux.intel.com>,
	<dmatlack@...gle.com>, <isaku.yamahata@...el.com>, <nik.borisov@...e.com>,
	<linux-kernel@...r.kernel.org>, <x86@...nel.org>, <yan.y.zhao@...el.com>,
	<weijiang.yang@...el.com>
Subject: Re: [PATCH 7/7] KVM: TDX: Add TSX_CTRL msr into uret_msrs list

>+static bool tdparams_tsx_supported(struct kvm_cpuid2 *cpuid)
>+{
>+	const struct kvm_cpuid_entry2 *entry;
>+	u64 mask;
>+	u32 ebx;
>+
>+	entry = kvm_find_cpuid_entry2(cpuid->entries, cpuid->nent, 0x7, 0);
>+	if (entry)
>+		ebx = entry->ebx;
>+	else
>+		ebx = 0;
>+
>+	mask = __feature_bit(X86_FEATURE_HLE) | __feature_bit(X86_FEATURE_RTM);
>+	return ebx & mask;
>+}
>+
> static int setup_tdparams(struct kvm *kvm, struct td_params *td_params,
> 			struct kvm_tdx_init_vm *init_vm)
> {
>@@ -1299,6 +1322,7 @@ static int setup_tdparams(struct kvm *kvm, struct td_params *td_params,
> 	MEMCPY_SAME_SIZE(td_params->mrowner, init_vm->mrowner);
> 	MEMCPY_SAME_SIZE(td_params->mrownerconfig, init_vm->mrownerconfig);
> 
>+	to_kvm_tdx(kvm)->tsx_supported = tdparams_tsx_supported(cpuid);
> 	return 0;
> }
> 
>@@ -2272,6 +2296,11 @@ static int __init __tdx_bringup(void)
> 			return -EIO;
> 		}
> 	}
>+	tdx_uret_tsx_ctrl_slot = kvm_find_user_return_msr(MSR_IA32_TSX_CTRL);
>+	if (tdx_uret_tsx_ctrl_slot == -1 && boot_cpu_has(X86_FEATURE_MSR_TSX_CTRL)) {
>+		pr_err("MSR_IA32_TSX_CTRL isn't included by kvm_find_user_return_msr\n");
>+		return -EIO;
>+	}
> 
> 	/*
> 	 * Enabling TDX requires enabling hardware virtualization first,
>diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
>index 48cf0a1abfcc..815ff6bdbc7e 100644
>--- a/arch/x86/kvm/vmx/tdx.h
>+++ b/arch/x86/kvm/vmx/tdx.h
>@@ -29,6 +29,14 @@ struct kvm_tdx {
> 	u8 nr_tdcs_pages;
> 	u8 nr_vcpu_tdcx_pages;
> 
>+	/*
>+	 * Used on each TD-exit, see tdx_user_return_msr_update_cache().
>+	 * TSX_CTRL value on TD exit
>+	 * - set 0     if guest TSX enabled
>+	 * - preserved if guest TSX disabled
>+	 */
>+	bool tsx_supported;

Is it possible to drop this boolean and tdparams_tsx_supported()? I think we
can use the guest_can_use() framework instead.

>+
> 	u64 tsc_offset;
> 
> 	enum kvm_tdx_state state;
>-- 
>2.43.0
>