mirror of https://gitee.com/openkylin/linux.git
KVM: PPC: Book3S HV: Fix H_CEDE return code for nested guests
The h_cede_tm kvm-unit-test currently fails when run inside an L1 guest
via the guest/nested hypervisor.
./run-tests.sh -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: 4bad77799f
("KVM: PPC: Book3S HV: Handle hypercalls correctly when nested")
Cc: linuxppc-dev@ozlabs.org
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
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@ -3615,6 +3615,7 @@ int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
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if (trap == BOOK3S_INTERRUPT_SYSCALL && !vcpu->arch.nested &&
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if (trap == BOOK3S_INTERRUPT_SYSCALL && !vcpu->arch.nested &&
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kvmppc_get_gpr(vcpu, 3) == H_CEDE) {
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kvmppc_get_gpr(vcpu, 3) == H_CEDE) {
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kvmppc_nested_cede(vcpu);
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kvmppc_nested_cede(vcpu);
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kvmppc_set_gpr(vcpu, 3, 0);
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trap = 0;
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trap = 0;
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}
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}
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} else {
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} else {
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