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Re: [PULL 15/22] x86: Grant AMX permission for guest
From: |
Daniel P . Berrangé |
Subject: |
Re: [PULL 15/22] x86: Grant AMX permission for guest |
Date: |
Wed, 16 Mar 2022 16:05:01 +0000 |
User-agent: |
Mutt/2.1.5 (2021-12-30) |
On Wed, Mar 16, 2022 at 04:57:39PM +0100, Peter Krempa wrote:
> On Tue, Mar 08, 2022 at 12:34:38 +0100, Paolo Bonzini wrote:
> > From: Yang Zhong <yang.zhong@intel.com>
> >
> > Kernel allocates 4K xstate buffer by default. For XSAVE features
> > which require large state component (e.g. AMX), Linux kernel
> > dynamically expands the xstate buffer only after the process has
> > acquired the necessary permissions. Those are called dynamically-
> > enabled XSAVE features (or dynamic xfeatures).
> >
> > There are separate permissions for native tasks and guests.
> >
> > Qemu should request the guest permissions for dynamic xfeatures
> > which will be exposed to the guest. This only needs to be done
> > once before the first vcpu is created.
> >
> > KVM implemented one new ARCH_GET_XCOMP_SUPP system attribute API to
> > get host side supported_xcr0 and Qemu can decide if it can request
> > dynamically enabled XSAVE features permission.
> > https://lore.kernel.org/all/20220126152210.3044876-1-pbonzini@redhat.com/
> >
> > Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> > Signed-off-by: Yang Zhong <yang.zhong@intel.com>
> > Signed-off-by: Jing Liu <jing2.liu@intel.com>
> > Message-Id: <20220217060434.52460-4-yang.zhong@intel.com>
> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> > ---
> > target/i386/cpu.c | 7 +++++
> > target/i386/cpu.h | 4 +++
> > target/i386/kvm/kvm-cpu.c | 12 ++++----
> > target/i386/kvm/kvm.c | 57 ++++++++++++++++++++++++++++++++++++++
> > target/i386/kvm/kvm_i386.h | 1 +
> > 5 files changed, 75 insertions(+), 6 deletions(-)
>
> With this commit qemu crashes for me when invoking the following
> QMP command:
It is way worse than that even. If you remove '-S' you get an
immediate kaboom on startup on AMD hosts
$ ./build/qemu-system-x86_64 -accel kvm
Unable to init server: Could not connect: Connection refused
qemu-system-x86_64: ../target/i386/kvm/kvm-cpu.c:105: kvm_cpu_xsave_init:
Assertion `esa->size == eax' failed.
Aborted (core dumped)
With regards,
Daniel
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- [PULL 07/22] update meson-buildoptions.sh, (continued)
- [PULL 07/22] update meson-buildoptions.sh, Paolo Bonzini, 2022/03/08
- [PULL 08/22] kvm-irqchip: introduce new API to support route change, Paolo Bonzini, 2022/03/08
- [PULL 10/22] target/i386: only include bits in pg_mode if they are not ignored, Paolo Bonzini, 2022/03/08
- [PULL 09/22] kvm/msi: do explicit commit when adding msi routes, Paolo Bonzini, 2022/03/08
- [PULL 13/22] x86: Fix the 64-byte boundary enumeration for extended state, Paolo Bonzini, 2022/03/08
- [PULL 16/22] x86: Add XFD faulting bit for state components, Paolo Bonzini, 2022/03/08
- [PULL 18/22] x86: add support for KVM_CAP_XSAVE2 and AMX state migration, Paolo Bonzini, 2022/03/08
- [PULL 20/22] i386: Add Icelake-Server-v6 CPU model with 5-level EPT support, Paolo Bonzini, 2022/03/08
- [PULL 15/22] x86: Grant AMX permission for guest, Paolo Bonzini, 2022/03/08
- Re: [PULL 15/22] x86: Grant AMX permission for guest, Yang Zhong, 2022/03/17
- Re: [PULL 15/22] x86: Grant AMX permission for guest, Michal Prívozník, 2022/03/18
- Re: [PULL 15/22] x86: Grant AMX permission for guest, Yang Zhong, 2022/03/18
- Re: [PULL 15/22] x86: Grant AMX permission for guest, Yang Zhong, 2022/03/22
[PULL 11/22] target/i386: Throw a #SS when loading a non-canonical IST, Paolo Bonzini, 2022/03/08
[PULL 22/22] gitlab-ci: do not run tests with address sanitizer, Paolo Bonzini, 2022/03/08