This is a note to let you know that I've just added the patch titled KVM: PPC: Book3S HV: Use GLOBAL_TOC for kvmppc_h_set_dabr/xdabr() to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-ppc-book3s-hv-use-global_toc-for-kvmppc_h_set_da.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 640babc6b55e1b48cd3920ce1c1f74b540c01590 Author: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Date: Fri Sep 24 01:10:31 2021 +1000 KVM: PPC: Book3S HV: Use GLOBAL_TOC for kvmppc_h_set_dabr/xdabr() [ 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@xxxxxxxxxxxxxx> Reviewed-by: Daniel Axtens <dja@xxxxxxxxxx> Link: https://lore.kernel.org/r/20210923151031.72408-1-mpe@xxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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: