From: Wen Pu <puwen@hygon.cn>
To: Tom Lendacky <thomas.lendacky@amd.com>,
"x86@kernel.org" <x86@kernel.org>
Cc: "joro@8bytes.org" <joro@8bytes.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>, "bp@suse.de" <bp@suse.de>,
"hpa@zytor.com" <hpa@zytor.com>,
"jroedel@suse.de" <jroedel@suse.de>,
"sashal@kernel.org" <sashal@kernel.org>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] x86/sev: Check whether SEV or SME is supported first
Date: Wed, 2 Jun 2021 06:55:05 +0000 [thread overview]
Message-ID: <8e1d7510-563a-3b54-6037-8c0904998123@hygon.cn> (raw)
In-Reply-To: <dc69a9bb-a4a0-d82b-2e9c-cf6336ab8252@amd.com>
On 2021/6/2 2:30, Tom Lendacky wrote:
> On 5/26/21 2:24 AM, Pu Wen wrote:
>> The first two bits of the CPUID leaf 0x8000001F EAX indicate whether
>> SEV or SME is supported respectively. It's better to check whether
>> SEV or SME is supported before checking the SEV MSR(0xc0010131) to
>> see whether SEV or SME is enabled.
>>
>> This also avoid the MSR reading failure on the first generation Hygon
>> Dhyana CPU which does not support SEV or SME.
>>
>> Fixes: eab696d8e8b9 ("x86/sev: Do not require Hypervisor CPUID bit for SEV guests")
>> Cc: <stable@vger.kernel.org> # v5.10+
>> Signed-off-by: Pu Wen <puwen@hygon.cn>
>
> I think the commit message needs to be expanded to clarify the situations
> and provide more detail.
Okay.
> This is both a bare-metal issue and a guest/VM issue. Since Hygon doesn't
> support the MSR_AMD64_SEV MSR, reading that MSR results in a #GP - either
> directly from hardware in the bare-metal case or via the hypervisor
> (because the RDMSR is actually intercepted) in the guest/VM case,
> resulting in a failed boot. And since this is very early in the boot
> phase, rdmsrl_safe()/native_read_msr_safe() can't be used.
The description is good, will add this.
> So by checking the CPUID information before attempting the RDMSR, this
> goes back to the behavior before the patch identified in the Fixes: tag.
>
> With an improved commit message:
>
> Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Thanks, will send patch v2 with improved commit messages.
--
Regards,
Pu Wen
>> ---
>> arch/x86/mm/mem_encrypt_identity.c | 11 ++++++-----
>> 1 file changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
>> index a9639f663d25..470b20208430 100644
>> --- a/arch/x86/mm/mem_encrypt_identity.c
>> +++ b/arch/x86/mm/mem_encrypt_identity.c
>> @@ -504,10 +504,6 @@ void __init sme_enable(struct boot_params *bp)
>> #define AMD_SME_BIT BIT(0)
>> #define AMD_SEV_BIT BIT(1)
>>
>> - /* Check the SEV MSR whether SEV or SME is enabled */
>> - sev_status = __rdmsr(MSR_AMD64_SEV);
>> - feature_mask = (sev_status & MSR_AMD64_SEV_ENABLED) ? AMD_SEV_BIT : AMD_SME_BIT;
>> -
>> /*
>> * Check for the SME/SEV feature:
>> * CPUID Fn8000_001F[EAX]
>> @@ -519,11 +515,16 @@ void __init sme_enable(struct boot_params *bp)
>> eax = 0x8000001f;
>> ecx = 0;
>> native_cpuid(&eax, &ebx, &ecx, &edx);
>> - if (!(eax & feature_mask))
>> + /* Check whether SEV or SME is supported */
>> + if (!(eax & (AMD_SEV_BIT | AMD_SME_BIT)))
>> return;
>>
>> me_mask = 1UL << (ebx & 0x3f);
>>
>> + /* Check the SEV MSR whether SEV or SME is enabled */
>> + sev_status = __rdmsr(MSR_AMD64_SEV);
>> + feature_mask = (sev_status & MSR_AMD64_SEV_ENABLED) ? AMD_SEV_BIT : AMD_SME_BIT;
>> +
>> /* Check if memory encryption is enabled */
>> if (feature_mask == AMD_SME_BIT) {
>> /*
>>
prev parent reply other threads:[~2021-06-02 6:57 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-26 7:24 [PATCH] x86/sev: Check whether SEV or SME is supported first Pu Wen
2021-05-26 17:27 ` Sean Christopherson
2021-05-27 15:08 ` Pu Wen
2021-05-31 9:37 ` Joerg Roedel
2021-05-31 14:56 ` Pu Wen
2021-06-01 14:39 ` Borislav Petkov
2021-06-01 16:14 ` Sean Christopherson
2021-06-01 16:36 ` Tom Lendacky
2021-06-01 16:59 ` Borislav Petkov
2021-06-01 17:16 ` Sean Christopherson
2021-06-01 17:48 ` Borislav Petkov
2021-06-01 18:08 ` Sean Christopherson
2021-06-01 18:24 ` Borislav Petkov
2021-06-01 17:09 ` Sean Christopherson
2021-06-01 18:30 ` Tom Lendacky
2021-06-02 6:55 ` Wen Pu [this message]
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