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[ Upstream commitdae5818646] kvmppc_h_set_dabr(), and kvmppc_h_set_xdabr() which jumps into it, need to use _GLOBAL_TOC to setup the kernel TOC pointer, because kvmppc_h_set_dabr() uses LOAD_REG_ADDR() to load dawr_force_enable. When called from hcall_try_real_mode() we have the kernel TOC in r2, established near the start of kvmppc_interrupt_hv(), so there is no issue. But they can also be called from kvmppc_pseries_do_hcall() which is module code, so the access ends up happening with the kvm-hv module's r2, which will not point at dawr_force_enable and could even cause a fault. With the current code layout and compilers we haven't observed a fault in practice, the load hits somewhere in kvm-hv.ko and silently returns some bogus value. Note that we we expect p8/p9 guests to use the DAWR, but SLOF uses h_set_dabr() to test if sc1 works correctly, see SLOF's lib/libhvcall/brokensc1.c. Fixes:c1fe190c06("powerpc: Add force enable of DAWR on P9 option") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Reviewed-by: Daniel Axtens <dja@axtens.net> Link: https://lore.kernel.org/r/20210923151031.72408-1-mpe@ellerman.id.au Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.