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

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Message-ID: <0e34f9d0-0927-4ac8-b1cb-ef8500b8d877@intel.com>
Date: Wed, 4 Dec 2024 08:18:32 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Chao Gao <chao.gao@...el.com>
Cc: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
 "seanjc@...gle.com" <seanjc@...gle.com>,
 "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
 "Li, Xiaoyao" <xiaoyao.li@...el.com>, "Huang, Kai" <kai.huang@...el.com>,
 "Zhao, Yan Y" <yan.y.zhao@...el.com>,
 "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "Yang, Weijiang" <weijiang.yang@...el.com>,
 "binbin.wu@...ux.intel.com" <binbin.wu@...ux.intel.com>,
 "dmatlack@...gle.com" <dmatlack@...gle.com>,
 "pbonzini@...hat.com" <pbonzini@...hat.com>,
 "Yamahata, Isaku" <isaku.yamahata@...el.com>,
 "tony.lindgren@...ux.intel.com" <tony.lindgren@...ux.intel.com>,
 "nik.borisov@...e.com" <nik.borisov@...e.com>,
 "Chatre, Reinette" <reinette.chatre@...el.com>,
 "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 7/7] KVM: TDX: Add TSX_CTRL msr into uret_msrs list

On 4/12/24 03:25, Chao Gao wrote:
>> +#define TDX_FEATURE_TSX (__feature_bit(X86_FEATURE_HLE) | __feature_bit(X86_FEATURE_RTM))
>> +
>> +static bool has_tsx(const struct kvm_cpuid_entry2 *entry)
>> +{
>> +	return entry->function == 7 && entry->index == 0 &&
>> +	       (entry->ebx & TDX_FEATURE_TSX);
>> +}
>> +
>> +static void clear_tsx(struct kvm_cpuid_entry2 *entry)
>> +{
>> +	entry->ebx &= ~TDX_FEATURE_TSX;
>> +}
>> +
>> +static bool has_waitpkg(const struct kvm_cpuid_entry2 *entry)
>> +{
>> +	return entry->function == 7 && entry->index == 0 &&
>> +	       (entry->ecx & __feature_bit(X86_FEATURE_WAITPKG));
>> +}
>> +
>> +static void clear_waitpkg(struct kvm_cpuid_entry2 *entry)
>> +{
>> +	entry->ecx &= ~__feature_bit(X86_FEATURE_WAITPKG);
>> +}
>> +
>> +static void tdx_clear_unsupported_cpuid(struct kvm_cpuid_entry2 *entry)
>> +{
>> +	if (has_tsx(entry))
>> +		clear_tsx(entry);
>> +
>> +	if (has_waitpkg(entry))
>> +		clear_waitpkg(entry);
>> +}
>> +
>> +static bool tdx_unsupported_cpuid(const struct kvm_cpuid_entry2 *entry)
>> +{
>> +	return has_tsx(entry) || has_waitpkg(entry);
>> +}
> 
> No need to check TSX/WAITPKG explicitly because setup_tdparams_cpuids() already
> ensures that unconfigurable bits are not set by userspace.

Aren't they configurable?

> 
>> +
>> #define KVM_TDX_CPUID_NO_SUBLEAF	((__u32)-1)
>>
>> static void td_init_cpuid_entry2(struct kvm_cpuid_entry2 *entry, unsigned char idx)
>> @@ -124,6 +162,8 @@ static void td_init_cpuid_entry2(struct kvm_cpuid_entry2 *entry, unsigned char i
>> 	/* Work around missing support on old TDX modules */
>> 	if (entry->function == 0x80000008)
>> 		entry->eax = tdx_set_guest_phys_addr_bits(entry->eax, 0xff);
>> +
>> +	tdx_clear_unsupported_cpuid(entry);
>> }
>>
>> static int init_kvm_tdx_caps(const struct tdx_sys_info_td_conf *td_conf,
>> @@ -1235,6 +1275,9 @@ static int setup_tdparams_cpuids(struct kvm_cpuid2 *cpuid,
>> 		if (!entry)
>> 			continue;
>>
>> +		if (tdx_unsupported_cpuid(entry))
>> +			return -EINVAL;
>> +
>> 		copy_cnt++;
>>
>> 		value = &td_params->cpuid_values[i];
>> -- 
>> 2.43.0
>>