From dae581864609d36fb58855fd59880b4941ce9d14 Mon Sep 17 00:00:00 2001

From: Michael Ellerman <mpe@ellerman.id.au>

Date: Fri, 24 Sep 2021 01:10:31 +1000

Subject: [PATCH] KVM: PPC: Book3S HV: Use GLOBAL_TOC for

 kvmppc_h_set_dabr/xdabr()

References: bsc#1156395

Patch-mainline: v5.16-rc2

Git-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

Acked-by: Michal Suchanek <msuchanek@suse.de>

---

 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 eb776d0c5d8e..32a4b4d412b9 100644

--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S

+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S

@@ -2005,7 +2005,7 @@ 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

@@ -2015,7 +2015,7 @@ 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:

-- 

2.35.3