From: "José Pekkarinen" <jose.pekkarinen@foxhound.fi>
To: Peter Gonda <pgonda@google.com>
Cc: x86@kernel.org, hpa@zytor.com, kvm@vger.kernel.org,
seanjc@google.com, dave.hansen@linux.intel.com,
linux-kernel@vger.kernel.org, mingo@redhat.com, bp@alien8.de,
pbonzini@redhat.com, tglx@linutronix.de,
linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [PATCH] kvm/sev: make SEV/SEV-ES asids configurable
Date: Tue, 10 Oct 2023 21:03:38 +0300 [thread overview]
Message-ID: <8fd78d002d84f3164eb5a9337e694fa1@foxhound.fi> (raw)
In-Reply-To: <CAMkAt6o7urak_kAjxEU4wtXv-mGOnyOYdcyhCRMfAG3MAOip0g@mail.gmail.com>
On 2023-10-10 19:49, Peter Gonda wrote:
> On Tue, Oct 10, 2023 at 5:22 AM José Pekkarinen
> <jose.pekkarinen@foxhound.fi> wrote:
>>
>> There are bioses that doesn't allow to configure the
>> number of asids allocated for SEV/SEV-ES, for those
>> cases, the default behaviour allocates all the asids
>> for SEV, leaving no room for SEV-ES to have some fun.
>> If the user request SEV-ES to be enabled, it will
>> find the kernel just run out of resources and ignored
>> user request. This following patch will address this
>> issue by making the number of asids for SEV/SEV-ES
>> configurable over kernel module parameters.
>>
>
> All this patch does is introduce an error case right? Because if the
> BIOS hasn't actually configured those SEV-ES asids and KVM tries to
> use an SEV as an SEV-ES asid commands to the ASP will fail, right?
>
> What happens when you try to create an SEV-ES VM with this patch, when
> the BIOS hasn't allocated any SEV-ES asids?
It still doesn't enable SEV-ES since the cpu exposes
min_sev_asids as 1, and there is a check to bail out in
the hardware setup function, so definitely this is not
fixing anything. I may not being understanding something
here though, since my BIOS doesn't seem to have any options
nor hints about SEV-ES, so I'm not quite sure it really
does something to provide the functionality. For the records
it is a Supermicro H11SSL-NC.
Thanks!
José.
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WARNING: multiple messages have this Message-ID (diff)
From: "José Pekkarinen" <jose.pekkarinen@foxhound.fi>
To: Peter Gonda <pgonda@google.com>
Cc: seanjc@google.com, pbonzini@redhat.com,
skhan@linuxfoundation.org, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org,
hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [PATCH] kvm/sev: make SEV/SEV-ES asids configurable
Date: Tue, 10 Oct 2023 21:03:38 +0300 [thread overview]
Message-ID: <8fd78d002d84f3164eb5a9337e694fa1@foxhound.fi> (raw)
In-Reply-To: <CAMkAt6o7urak_kAjxEU4wtXv-mGOnyOYdcyhCRMfAG3MAOip0g@mail.gmail.com>
On 2023-10-10 19:49, Peter Gonda wrote:
> On Tue, Oct 10, 2023 at 5:22 AM José Pekkarinen
> <jose.pekkarinen@foxhound.fi> wrote:
>>
>> There are bioses that doesn't allow to configure the
>> number of asids allocated for SEV/SEV-ES, for those
>> cases, the default behaviour allocates all the asids
>> for SEV, leaving no room for SEV-ES to have some fun.
>> If the user request SEV-ES to be enabled, it will
>> find the kernel just run out of resources and ignored
>> user request. This following patch will address this
>> issue by making the number of asids for SEV/SEV-ES
>> configurable over kernel module parameters.
>>
>
> All this patch does is introduce an error case right? Because if the
> BIOS hasn't actually configured those SEV-ES asids and KVM tries to
> use an SEV as an SEV-ES asid commands to the ASP will fail, right?
>
> What happens when you try to create an SEV-ES VM with this patch, when
> the BIOS hasn't allocated any SEV-ES asids?
It still doesn't enable SEV-ES since the cpu exposes
min_sev_asids as 1, and there is a check to bail out in
the hardware setup function, so definitely this is not
fixing anything. I may not being understanding something
here though, since my BIOS doesn't seem to have any options
nor hints about SEV-ES, so I'm not quite sure it really
does something to provide the functionality. For the records
it is a Supermicro H11SSL-NC.
Thanks!
José.
next prev parent reply other threads:[~2023-10-10 18:11 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-10 10:04 [PATCH] kvm/sev: make SEV/SEV-ES asids configurable José Pekkarinen
2023-10-10 10:04 ` José Pekkarinen
2023-10-10 11:35 ` Greg KH
2023-10-10 11:35 ` Greg KH
2023-10-10 11:40 ` Paolo Bonzini
2023-10-10 11:40 ` Paolo Bonzini
2023-10-10 12:20 ` José Pekkarinen
2023-10-10 12:20 ` José Pekkarinen
2023-10-10 12:01 ` José Pekkarinen
2023-10-10 12:01 ` José Pekkarinen
2023-10-10 16:49 ` Peter Gonda via Linux-kernel-mentees
2023-10-10 16:49 ` Peter Gonda
2023-10-10 18:03 ` José Pekkarinen [this message]
2023-10-10 18:03 ` José Pekkarinen
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