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)