blob: de3661e4f099fb30a147c8d9711ef6ef5a103f6b [file] [log] [blame]
From 56ee8ce78cb5501cb162bd3d3d13cd20321712bc Mon Sep 17 00:00:00 2001
From: Michael Roth <>
Date: Tue, 10 Mar 2020 16:11:28 -0500
Subject: [PATCH] KVM: PPC: Book3S HV: Fix H_CEDE return code for nested guests
commit 1f50cc1705350a4697923203fedd7d8fb1087fe2 upstream.
The h_cede_tm kvm-unit-test currently fails when run inside an L1 guest
via the guest/nested hypervisor.
./ -v
TESTNAME=h_cede_tm TIMEOUT=90s ACCEL= ./powerpc/run powerpc/tm.elf -smp 2,threads=2 -machine cap-htm=on -append "h_cede_tm"
FAIL h_cede_tm (2 tests, 1 unexpected failures)
While the test relates to transactional memory instructions, the actual
failure is due to the return code of the H_CEDE hypercall, which is
reported as 224 instead of 0. This happens even when no TM instructions
are issued.
224 is the value placed in r3 to execute a hypercall for H_CEDE, and r3
is where the caller expects the return code to be placed upon return.
In the case of guest running under a nested hypervisor, issuing H_CEDE
causes a return from H_ENTER_NESTED. In this case H_CEDE is
specially-handled immediately rather than later in
kvmppc_pseries_do_hcall() as with most other hcalls, but we forget to
set the return code for the caller, hence why kvm-unit-test sees the
224 return code and reports an error.
Guest kernels generally don't check the return value of H_CEDE, so
that likely explains why this hasn't caused issues outside of
kvm-unit-tests so far.
Fix this by setting r3 to 0 after we finish processing the H_CEDE.
RHBZ: 1778556
Fixes: 4bad77799fed ("KVM: PPC: Book3S HV: Handle hypercalls correctly when nested")
Cc: David Gibson <>
Cc: Paul Mackerras <>
Signed-off-by: Michael Roth <>
Reviewed-by: David Gibson <>
Signed-off-by: Paul Mackerras <>
Signed-off-by: Paul Gortmaker <>
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index a46f93045fea..cc4279bc6da6 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -3620,6 +3620,7 @@ int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
if (trap == BOOK3S_INTERRUPT_SYSCALL && !vcpu->arch.nested &&
kvmppc_get_gpr(vcpu, 3) == H_CEDE) {
+ kvmppc_set_gpr(vcpu, 3, 0);
trap = 0;
} else {