From: Michael Ellerman mpe@ellerman.id.au
[ Upstream commit dae581864609d36fb58855fd59880b4941ce9d14 ]
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: c1fe190c0672 ("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 --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index f9c7326672b95..c9c6619564ffa 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -2535,7 +2535,7 @@ hcall_real_table: .globl hcall_real_table_end hcall_real_table_end:
-_GLOBAL(kvmppc_h_set_xdabr) +_GLOBAL_TOC(kvmppc_h_set_xdabr) EXPORT_SYMBOL_GPL(kvmppc_h_set_xdabr) andi. r0, r5, DABRX_USER | DABRX_KERNEL beq 6f @@ -2545,7 +2545,7 @@ EXPORT_SYMBOL_GPL(kvmppc_h_set_xdabr) 6: li r3, H_PARAMETER blr
-_GLOBAL(kvmppc_h_set_dabr) +_GLOBAL_TOC(kvmppc_h_set_dabr) EXPORT_SYMBOL_GPL(kvmppc_h_set_dabr) li r5, DABRX_USER | DABRX_KERNEL 3: