forked from Minki/linux
8563bf52d5
The DABRX (DABR extension) register on POWER7 processors provides finer control over which accesses cause a data breakpoint interrupt. It contains 3 bits which indicate whether to enable accesses in user, kernel and hypervisor modes respectively to cause data breakpoint interrupts, plus one bit that enables both real mode and virtual mode accesses to cause interrupts. Currently, KVM sets DABRX to allow both kernel and user accesses to cause interrupts while in the guest. This adds support for the guest to specify other values for DABRX. PAPR defines a H_SET_XDABR hcall to allow the guest to set both DABR and DABRX with one call. This adds a real-mode implementation of H_SET_XDABR, which shares most of its code with the existing H_SET_DABR implementation. To support this, we add a per-vcpu field to store the DABRX value plus code to get and set it via the ONE_REG interface. For Linux guests to use this new hcall, userspace needs to add "hcall-xdabr" to the set of strings in the /chosen/hypertas-functions property in the device tree. If userspace does this and then migrates the guest to a host where the kernel doesn't include this patch, then userspace will need to implement H_SET_XDABR by writing the specified DABR value to the DABR using the ONE_REG interface. In that case, the old kernel will set DABRX to DABRX_USER | DABRX_KERNEL. That should still work correctly, at least for Linux guests, since Linux guests cope with getting data breakpoint interrupts in modes that weren't requested by just ignoring the interrupt, and Linux guests never set DABRX_BTI. The other thing this does is to make H_SET_DABR and H_SET_XDABR work on POWER8, which has the DAWR and DAWRX instead of DABR/X. Guests that know about POWER8 should use H_SET_MODE rather than H_SET_[X]DABR, but guests running in POWER7 compatibility mode will still use H_SET_[X]DABR. For them, this adds the logic to convert DABR/X values into DAWR/X values on POWER8. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Alexander Graf <agraf@suse.de> |
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