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:
