linux-kernel - [PATCH v7 0/4] KVM: nSVM: ondemand nested state allocation

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Message-Id: <20201001112954.6258-1-mlevitsk@redhat.com>
Date:   Thu,  1 Oct 2020 14:29:50 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Borislav Petkov <bp@...en8.de>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH v7 0/4] KVM: nSVM: ondemand nested state allocation

This is the next version of this patch series.

In V5 I adopted Sean Christopherson's suggestion to make .set_efer return
a negative error (-ENOMEM in this case) which in most cases in kvm
propagates to the userspace.

I noticed though that wrmsr emulation code doesn't do this and instead
it injects #GP to the guest on _any_ error.

So I fixed the wrmsr code to behave in a similar way to the rest
of the kvm code.
(#GP only on a positive error value, and forward the negative error to
the userspace)

I had to adjust one wrmsr handler (xen_hvm_config) to stop it from returning
negative values	so that new WRMSR emulation behavior doesn't break it.
This patch was only compile tested.

The memory allocation failure was tested by always returning -ENOMEM
from svm_allocate_nested.

The nested allocation itself was tested by countless attempts to run
nested guests, do nested migration on both my AMD and Intel machines.
I wasn't able to break it.

Changes from V5: addressed Sean Christopherson's review feedback.
Changes from V6: rebased the code on latest kvm/queue

Best regards,
	Maxim Levitsky

Maxim Levitsky (4):
  KVM: x86: xen_hvm_config: cleanup return values
  KVM: x86: report negative values from wrmsr emulation to userspace
  KVM: x86: allow kvm_x86_ops.set_efer to return an error value
  KVM: nSVM: implement on demand allocation of the nested state

 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/emulate.c          |  4 +--
 arch/x86/kvm/svm/nested.c       | 42 ++++++++++++++++++++++
 arch/x86/kvm/svm/svm.c          | 64 ++++++++++++++++++---------------
 arch/x86/kvm/svm/svm.h          | 10 +++++-
 arch/x86/kvm/vmx/vmx.c          |  6 ++--
 arch/x86/kvm/x86.c              | 39 ++++++++++----------
 7 files changed, 114 insertions(+), 53 deletions(-)

-- 
2.26.2