• Marc Zyngier's avatar
    arm: KVM: force execution of HCPTR access on VM exit · 85e84ba3
    Marc Zyngier authored
    On VM entry, we disable access to the VFP registers in order to
    perform a lazy save/restore of these registers.
    
    On VM exit, we restore access, test if we did enable them before,
    and save/restore the guest/host registers if necessary. In this
    sequence, the FPEXC register is always accessed, irrespective
    of the trapping configuration.
    
    If the guest didn't touch the VFP registers, then the HCPTR access
    has now enabled such access, but we're missing a barrier to ensure
    architectural execution of the new HCPTR configuration. If the HCPTR
    access has been delayed/reordered, the subsequent access to FPEXC
    will cause a trap, which we aren't prepared to handle at all.
    
    The same condition exists when trapping to enable VFP for the guest.
    
    The fix is to introduce a barrier after enabling VFP access. In the
    vmexit case, it can be relaxed to only takes place if the guest hasn't
    accessed its view of the VFP registers, making the access to FPEXC safe.
    
    The set_hcptr macro is modified to deal with both vmenter/vmexit and
    vmtrap operations, and now takes an optional label that is branched to
    when the guest hasn't touched the VFP registers.
    Reported-by: default avatarVikram Sethi <vikrams@codeaurora.org>
    Cc: stable@kernel.org	# v3.9+
    Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
    85e84ba3
interrupts.S 13.2 KB