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From: Sean Christopherson <firstname.lastname@example.org>
To: Brijesh Singh <email@example.com>
Cc: Mingwei Zhang <firstname.lastname@example.org>,
Paolo Bonzini <email@example.com>,
Tom Lendacky <firstname.lastname@example.org>,
John Allen <email@example.com>,
Vitaly Kuznetsov <firstname.lastname@example.org>,
Wanpeng Li <email@example.com>,
Jim Mattson <firstname.lastname@example.org>, Joerg Roedel <email@example.com>,
firstname.lastname@example.org, Alper Gun <email@example.com>,
Borislav Petkov <firstname.lastname@example.org>,
David Rienjes <email@example.com>,
Marc Orr <firstname.lastname@example.org>, Peter Gonda <email@example.com>,
Vipin Sharma <firstname.lastname@example.org>
Subject: Re: [PATCH v2 3/4] KVM: SVM: move sev_bind_asid to psp
Date: Thu, 9 Sep 2021 18:13:05 +0000 [thread overview]
Message-ID: <YTpOsUAqHjQ9DDLd@google.com> (raw)
On Thu, Sep 09, 2021, Brijesh Singh wrote:
> On 9/7/21 6:37 PM, Sean Christopherson wrote:
> > On Tue, Sep 07, 2021, Brijesh Singh wrote:
> > > I have no strong preference for either of the abstraction approaches. The
> > > sheer number of argument can also make some folks wonder whether such
> > > abstraction makes it easy to read. e.g send-start may need up to 11.
> > Yeah, that's brutal, but IMO having a few ugly functions is an acceptable cost if
> > it means the rest of the API is cleaner. E.g. KVM is not the right place to
> > implement sev_deactivate_lock, as any coincident DEACTIVATE will be problematic.
> > The current code "works" because KVM is the only in-tree user, but even that's a
> > bit of a grey area because sev_guest_deactivate() is exported.
> > If large param lists are problematic, one idea would be to reuse the sev_data_*
> > structs for the API. I still don't like the idea of exposing those structs
> > outside of the PSP driver, and the potential user vs. kernel pointer confusion
> > is more than a bit ugly. On the other hand it's not exactly secret info,
> > e.g. KVM's UAPI structs are already excrutiatingly close to sev_data_* structs.
> > For future ioctls(), KVM could even define UAPI structs that are bit-for-bit
> > compatible with the hardware structs. That would allow KVM to copy userspace's
> > data directly into a "struct sev_data_*" and simply require the handle and any
> > other KVM-defined params to be zero. KVM could then hand the whole struct over
> > to the PSP driver for processing.
> Most of the address field in the "struct sev_data_*" are physical
> addressess. The userspace will not be able to populate those fields.
Yeah, that's my biggest hesitation to using struct sev_data_* in the API, it's
both confusing and gross. But it's also why I think these helpers belong in the
PSP driver, KVM should not need to know the "on-the-wire" format for communicating
with the PSP.
> PSP or KVM may still need to assist filling the final hardware structure.
> Some of fields in hardware structure must be zero, so we need to add checks
> for it.
> I can try posting RFC post SNP series and we can see how it all looks.
I'm a bit torn. I completely understand the desire to get SNP support merged, but
at the same time KVM has accrued a fair bit of technical debt for SEV and SEV-ES,
and the lack of tests is also a concern. I don't exactly love the idea of kicking
those cans further down the road.
Paolo, any thoughts?
next prev parent reply other threads:[~2021-09-09 18:13 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-18 5:39 [PATCH v2 0/4] clean up interface between KVM and psp Mingwei Zhang
2021-08-18 5:39 ` [PATCH v2 1/4] KVM: SVM: fix missing sev_decommission in sev_receive_start Mingwei Zhang
2021-08-21 2:11 ` Marc Orr
2021-08-21 2:30 ` Marc Orr
2021-08-18 5:39 ` [PATCH v2 2/4] KVM: SVM: move sev_decommission to psp driver Mingwei Zhang
2021-08-18 5:39 ` [PATCH v2 3/4] KVM: SVM: move sev_bind_asid to psp Mingwei Zhang
2021-09-03 19:38 ` Sean Christopherson
2021-09-07 16:30 ` Brijesh Singh
2021-09-07 23:37 ` Sean Christopherson
2021-09-09 16:07 ` Brijesh Singh
2021-09-09 18:13 ` Sean Christopherson [this message]
2021-09-09 21:18 ` Mingwei Zhang
2021-09-09 22:25 ` Brijesh Singh
2021-09-10 1:18 ` Mingwei Zhang
2021-09-10 1:23 ` Marc Orr
2021-08-18 5:39 ` [PATCH v2 4/4] KVM: SVM: move sev_unbind_asid and DF_FLUSH logic into psp Mingwei Zhang
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