linux-kernel - KVM: x86: Pass additional FPU bits to the guest

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Message-Id: <20190925213721.21245-1-bigeasy@linutronix.de>
Date:   Wed, 25 Sep 2019 23:37:19 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: KVM: x86: Pass additional FPU bits to the guest

While testing my FPU patches on AMD's ZEN platform I noticed that the
XSAVES feature flag was never used in the guest while it was present in
the host. Patch #1 seemed to work but I holded on to it because I could
explain why the guest did report ´fxsave_leak' while the host did not.
It turns out that I need #2 _and_ tell qemu not to mask this information
away.

Sebastian