* [PATCH] KVM: PPC: Book3S HV: Fix H_CEDE return code for nested guests
@ 2020-03-10 21:11 ` Michael Roth
0 siblings, 0 replies; 6+ messages in thread
From: Michael Roth @ 2020-03-10 21:11 UTC (permalink / raw)
To: kvm-ppc; +Cc: linuxppc-dev, David Gibson
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: 4bad77799fed ("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>
---
arch/powerpc/kvm/book3s_hv.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 2cefd071b848..c0c43a733830 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -3616,6 +3616,7 @@ 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_nested_cede(vcpu);
+ kvmppc_set_gpr(vcpu, 3, 0);
trap = 0;
}
} else {
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH] KVM: PPC: Book3S HV: Fix H_CEDE return code for nested guests
@ 2020-03-10 21:11 ` Michael Roth
0 siblings, 0 replies; 6+ messages in thread
From: Michael Roth @ 2020-03-10 21:11 UTC (permalink / raw)
To: kvm-ppc; +Cc: linuxppc-dev, David Gibson
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 TIMEOUTês 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: 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>
---
arch/powerpc/kvm/book3s_hv.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 2cefd071b848..c0c43a733830 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -3616,6 +3616,7 @@ 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_nested_cede(vcpu);
+ kvmppc_set_gpr(vcpu, 3, 0);
trap = 0;
}
} else {
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: PPC: Book3S HV: Fix H_CEDE return code for nested guests
2020-03-10 21:11 ` Michael Roth
@ 2020-03-10 23:05 ` David Gibson
-1 siblings, 0 replies; 6+ messages in thread
From: David Gibson @ 2020-03-10 23:05 UTC (permalink / raw)
To: Michael Roth; +Cc: linuxppc-dev, kvm-ppc
[-- Attachment #1: Type: text/plain, Size: 2547 bytes --]
On Tue, Mar 10, 2020 at 04:11:28PM -0500, Michael Roth wrote:
> 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: 4bad77799fed ("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>
> ---
> arch/powerpc/kvm/book3s_hv.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 2cefd071b848..c0c43a733830 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -3616,6 +3616,7 @@ 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_nested_cede(vcpu);
> + kvmppc_set_gpr(vcpu, 3, 0);
> trap = 0;
> }
> } else {
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: PPC: Book3S HV: Fix H_CEDE return code for nested guests
@ 2020-03-10 23:05 ` David Gibson
0 siblings, 0 replies; 6+ messages in thread
From: David Gibson @ 2020-03-10 23:05 UTC (permalink / raw)
To: Michael Roth; +Cc: linuxppc-dev, kvm-ppc
[-- Attachment #1: Type: text/plain, Size: 2547 bytes --]
On Tue, Mar 10, 2020 at 04:11:28PM -0500, Michael Roth wrote:
> 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: 4bad77799fed ("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>
> ---
> arch/powerpc/kvm/book3s_hv.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 2cefd071b848..c0c43a733830 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -3616,6 +3616,7 @@ 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_nested_cede(vcpu);
> + kvmppc_set_gpr(vcpu, 3, 0);
> trap = 0;
> }
> } else {
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: PPC: Book3S HV: Fix H_CEDE return code for nested guests
2020-03-10 21:11 ` Michael Roth
@ 2020-03-19 23:32 ` Paul Mackerras
-1 siblings, 0 replies; 6+ messages in thread
From: Paul Mackerras @ 2020-03-19 23:32 UTC (permalink / raw)
To: Michael Roth; +Cc: linuxppc-dev, kvm-ppc, David Gibson
On Tue, Mar 10, 2020 at 04:11:28PM -0500, Michael Roth wrote:
> 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: 4bad77799fed ("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>
Thanks, applied to my kvm-ppc-next branch.
Paul.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] KVM: PPC: Book3S HV: Fix H_CEDE return code for nested guests
@ 2020-03-19 23:32 ` Paul Mackerras
0 siblings, 0 replies; 6+ messages in thread
From: Paul Mackerras @ 2020-03-19 23:32 UTC (permalink / raw)
To: Michael Roth; +Cc: linuxppc-dev, kvm-ppc, David Gibson
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="windows-1252", Size: 1752 bytes --]
On Tue, Mar 10, 2020 at 04:11:28PM -0500, Michael Roth wrote:
> 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 TIMEOUTs 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: 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>
Thanks, applied to my kvm-ppc-next branch.
Paul.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-03-19 23:39 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2020-03-10 21:11 [PATCH] KVM: PPC: Book3S HV: Fix H_CEDE return code for nested guests Michael Roth
2020-03-10 21:11 ` Michael Roth
2020-03-10 23:05 ` David Gibson
2020-03-10 23:05 ` David Gibson
2020-03-19 23:32 ` Paul Mackerras
2020-03-19 23:32 ` Paul Mackerras
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