From: Laurent Dufour <ldufour@linux.ibm.com>
To: bharata@linux.ibm.com
Cc: linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 2/2] KVM: PPC: Book3S HV: H_SVM_INIT_START must call UV_RETURN
Date: Fri, 20 Mar 2020 15:36:05 +0100 [thread overview]
Message-ID: <f6a71da6-6363-8cba-8215-78b23a046443@linux.ibm.com> (raw)
In-Reply-To: <20200320112403.GG26049@in.ibm.com>
Le 20/03/2020 à 12:24, Bharata B Rao a écrit :
> On Fri, Mar 20, 2020 at 11:26:43AM +0100, Laurent Dufour wrote:
>> When the call to UV_REGISTER_MEM_SLOT is failing, for instance because
>> there is not enough free secured memory, the Hypervisor (HV) has to call
>> UV_RETURN to report the error to the Ultravisor (UV). Then the UV will call
>> H_SVM_INIT_ABORT to abort the securing phase and go back to the calling VM.
>>
>> If the kvm->arch.secure_guest is not set, in the return path rfid is called
>> but there is no valid context to get back to the SVM since the Hcall has
>> been routed by the Ultravisor.
>>
>> Move the setting of kvm->arch.secure_guest earlier in
>> kvmppc_h_svm_init_start() so in the return path, UV_RETURN will be called
>> instead of rfid.
>>
>> Cc: Bharata B Rao <bharata@linux.ibm.com>
>> Cc: Paul Mackerras <paulus@ozlabs.org>
>> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>> Cc: Michael Ellerman <mpe@ellerman.id.au>
>> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
>> ---
>> arch/powerpc/kvm/book3s_hv_uvmem.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
>> index 79b1202b1c62..68dff151315c 100644
>> --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
>> +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
>> @@ -209,6 +209,8 @@ unsigned long kvmppc_h_svm_init_start(struct kvm *kvm)
>> int ret = H_SUCCESS;
>> int srcu_idx;
>>
>> + kvm->arch.secure_guest = KVMPPC_SECURE_INIT_START;
>> +
>> if (!kvmppc_uvmem_bitmap)
>> return H_UNSUPPORTED;
>>
>> @@ -233,7 +235,6 @@ unsigned long kvmppc_h_svm_init_start(struct kvm *kvm)
>> goto out;
>> }
>> }
>> - kvm->arch.secure_guest |= KVMPPC_SECURE_INIT_START;
>
> There is an assumption that memory slots would have been registered with UV
> if KVMPPC_SECURE_INIT_START has been done. KVM_PPC_SVM_OFF ioctl will skip
> unregistration and other steps during reboot if KVMPPC_SECURE_INIT_START
> hasn't been done.
>
> Have you checked if that path isn't affected by this change?
I checked that and didn't find any issue there.
My only concern was that block:
kvm_for_each_vcpu(i, vcpu, kvm) {
spin_lock(&vcpu->arch.vpa_update_lock);
unpin_vpa_reset(kvm, &vcpu->arch.dtl);
unpin_vpa_reset(kvm, &vcpu->arch.slb_shadow);
unpin_vpa_reset(kvm, &vcpu->arch.vpa);
spin_unlock(&vcpu->arch.vpa_update_lock);
}
But that seems to be safe.
However I'm not a familiar with the KVM's code, do you think an additional
KVMPPC_SECURE_INIT_* value needed here?
Thanks,
Laurent.
next prev parent reply other threads:[~2020-03-20 14:45 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 10:26 [PATCH 0/2] Fix SVM hang at startup Laurent Dufour
2020-03-20 10:26 ` [PATCH 1/2] KVM: PPC: Book3S HV: check caller of H_SVM_* Hcalls Laurent Dufour
2020-03-20 12:22 ` Greg Kurz
2020-03-20 14:43 ` Laurent Dufour
2020-03-23 23:43 ` Paul Mackerras
2020-03-24 12:00 ` Greg Kurz
2020-03-24 13:13 ` Laurent Dufour
2020-03-21 0:40 ` Ram Pai
2020-03-20 10:26 ` [PATCH 2/2] KVM: PPC: Book3S HV: H_SVM_INIT_START must call UV_RETURN Laurent Dufour
2020-03-20 11:24 ` Bharata B Rao
2020-03-20 14:36 ` Laurent Dufour [this message]
2020-03-23 4:21 ` Bharata B Rao
2020-03-21 0:47 ` Ram Pai
2020-03-23 14:09 ` Fabiano Rosas
2020-03-24 2:54 ` [PATCH 0/2] Fix SVM hang at startup Paul Mackerras
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f6a71da6-6363-8cba-8215-78b23a046443@linux.ibm.com \
--to=ldufour@linux.ibm.com \
--cc=bharata@linux.ibm.com \
--cc=kvm-ppc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).