[PATCH V3 2/2] KVM: PPC: Implement H_SVM_INIT_ABORT hcall
Ram Pai
linuxram at us.ibm.com
Fri Jan 3 11:18:14 AEDT 2020
On Sat, Dec 14, 2019 at 06:12:08PM -0800, Sukadev Bhattiprolu wrote:
>
> Implement the H_SVM_INIT_ABORT hcall which the Ultravisor can use to
> abort an SVM after it has issued the H_SVM_INIT_START and before the
> H_SVM_INIT_DONE hcalls. This hcall could be used when Ultravisor
> encounters security violations or other errors when starting an SVM.
>
> Note that this hcall is different from UV_SVM_TERMINATE ucall which
> is used by HV to terminate/cleanup an VM that has becore secure.
>
> The H_SVM_INIT_ABORT should basically undo operations that were done
> since the H_SVM_INIT_START hcall - i.e page-out all the VM pages back
> to normal memory, and terminate the SVM.
>
> (If we do not bring the pages back to normal memory, the text/data
> of the VM would be stuck in secure memory and since the SVM did not
> go secure, its MSR_S bit will be clear and the VM wont be able to
> access its pages even to do a clean exit).
>
> Based on patches and discussion with Paul Mackerras, Ram Pai and
> Bharata Rao.
>
> Signed-off-by: Ram Pai <linuxram at linux.ibm.com>
> Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.ibm.com>
> Signed-off-by: Bharata B Rao <bharata at linux.ibm.com>
> ---
> Changelog[v3]:
> - Rather than pass the NIP/MSR as parameters, load them into
> SRR0/SRR1 (like we do with other registers) and terminate
> the VM after paging out pages
> - Move the code to add a skip_page_out parameter into a
> separate patch.
>
> Changelog[v2]:
> [Paul Mackerras] avoid returning to UV "one last time" after
> the state is cleaned up. So, we now have H_SVM_INIT_ABORT:
> - take the VM's NIP/MSR register states as parameters
> - inherit the state of other registers as at UV_ESM call.
> After cleaning up the partial state, HV uses these to return
> directly to the VM with a failed UV_ESM call.
> ---
> Documentation/powerpc/ultravisor.rst | 57 +++++++++++++++++++++
> arch/powerpc/include/asm/hvcall.h | 1 +
> arch/powerpc/include/asm/kvm_book3s_uvmem.h | 6 +++
> arch/powerpc/include/asm/kvm_host.h | 1 +
> arch/powerpc/kvm/book3s_hv.c | 3 ++
> arch/powerpc/kvm/book3s_hv_uvmem.c | 24 +++++++++
> 6 files changed, 92 insertions(+)
>
> diff --git a/Documentation/powerpc/ultravisor.rst b/Documentation/powerpc/ultravisor.rst
> index 730854f73830..8c114c071bfa 100644
> --- a/Documentation/powerpc/ultravisor.rst
> +++ b/Documentation/powerpc/ultravisor.rst
> @@ -948,6 +948,63 @@ Use cases
> up its internal state for this virtual machine.
>
>
> +H_SVM_INIT_ABORT
> +----------------
> +
> + Abort the process of securing an SVM.
> +
> +Syntax
> +~~~~~~
> +
> +.. code-block:: c
> +
> + uint64_t hypercall(const uint64_t H_SVM_INIT_ABORT)
> +
> +Return values
> +~~~~~~~~~~~~~
> +
> + One of the following values:
> +
> + * H_PARAMETER on successfully cleaning up the state,
> + Hypervisor will return this value to the
> + **guest**, to indicate that the underlying
> + UV_ESM ultracall failed.
> +
> + * H_UNSUPPORTED if called from the wrong context (e.g. from
> + an SVM or before an H_SVM_INIT_START hypercall).
> +
> +Description
> +~~~~~~~~~~~
> +
> + Abort the process of securing a virtual machine. This call must
> + be made after a prior call to ``H_SVM_INIT_START`` hypercall and
> + before a call to ``H_SVM_INIT_DONE``.
> +
> + On entry into this hypercall the non-volatile GPRs and FPRs are
> + expected to contain the values they had at the time the VM issued
> + the UV_ESM ultracall. Further ``SRR0`` is expected to contain the
> + address of the instruction after the ``UV_ESM`` ultracall and ``SRR1``
> + the MSR value with which to return to the VM.
> +
> + This hypercall will cleanup any partial state that was established for
> + the VM since the prior ``H_SVM_INIT_START`` hypercall, including paging
> + out pages that were paged-into secure memory, and issue the
> + ``UV_SVM_TERMINATE`` ultracall to terminate the VM.
> +
> + After the partial state is cleaned up, control returns to the VM
> + (**not Ultravisor**), at the address specified in ``SRR0`` with the
> + MSR values set to the value in ``SRR1``.
> +
> +Use cases
> +~~~~~~~~~
> +
> + If after a successful call to ``H_SVM_INIT_START``, the Ultravisor
> + encounters an error while securing a virtual machine, either due
> + to lack of resources or because the VM's security information could
> + not be validated, Ultravisor informs the Hypervisor about it.
> + Hypervisor should use this call to clean up any internal state for
> + this virtual machine and return to the VM.
> +
> H_SVM_PAGE_IN
> -------------
>
> diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
> index 13bd870609c3..e90c073e437e 100644
> --- a/arch/powerpc/include/asm/hvcall.h
> +++ b/arch/powerpc/include/asm/hvcall.h
> @@ -350,6 +350,7 @@
> #define H_SVM_PAGE_OUT 0xEF04
> #define H_SVM_INIT_START 0xEF08
> #define H_SVM_INIT_DONE 0xEF0C
> +#define H_SVM_INIT_ABORT 0xEF14
>
> /* Values for 2nd argument to H_SET_MODE */
> #define H_SET_MODE_RESOURCE_SET_CIABR 1
> diff --git a/arch/powerpc/include/asm/kvm_book3s_uvmem.h b/arch/powerpc/include/asm/kvm_book3s_uvmem.h
> index 3cf8425b9838..5a9834e0e2d1 100644
> --- a/arch/powerpc/include/asm/kvm_book3s_uvmem.h
> +++ b/arch/powerpc/include/asm/kvm_book3s_uvmem.h
> @@ -19,6 +19,7 @@ unsigned long kvmppc_h_svm_page_out(struct kvm *kvm,
> unsigned long kvmppc_h_svm_init_start(struct kvm *kvm);
> unsigned long kvmppc_h_svm_init_done(struct kvm *kvm);
> int kvmppc_send_page_to_uv(struct kvm *kvm, unsigned long gfn);
> +unsigned long kvmppc_h_svm_init_abort(struct kvm *kvm);
> void kvmppc_uvmem_drop_pages(const struct kvm_memory_slot *free,
> struct kvm *kvm, bool skip_page_out);
> #else
> @@ -62,6 +63,11 @@ static inline unsigned long kvmppc_h_svm_init_done(struct kvm *kvm)
> return H_UNSUPPORTED;
> }
>
> +static inline unsigned long kvmppc_h_svm_init_abort(struct kvm *kvm)
> +{
> + return H_UNSUPPORTED;
> +}
> +
> static inline int kvmppc_send_page_to_uv(struct kvm *kvm, unsigned long gfn)
> {
> return -EFAULT;
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index 577ca95fac7c..8310c0407383 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -278,6 +278,7 @@ struct kvm_resize_hpt;
> /* Flag values for kvm_arch.secure_guest */
> #define KVMPPC_SECURE_INIT_START 0x1 /* H_SVM_INIT_START has been called */
> #define KVMPPC_SECURE_INIT_DONE 0x2 /* H_SVM_INIT_DONE completed */
> +#define KVMPPC_SECURE_INIT_ABORT 0x4 /* H_SVM_INIT_ABORT issued */
>
> struct kvm_arch {
> unsigned int lpid;
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 66d5312be16b..1b22f2c7ad1b 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -1099,6 +1099,9 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
> case H_SVM_INIT_DONE:
> ret = kvmppc_h_svm_init_done(vcpu->kvm);
> break;
> + case H_SVM_INIT_ABORT:
> + ret = kvmppc_h_svm_init_abort(vcpu->kvm);
> + break;
>
> default:
> return RESUME_HOST;
> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
> index 9a5bbad7d87e..f7df8c327468 100644
> --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
> +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
> @@ -287,6 +287,30 @@ void kvmppc_uvmem_drop_pages(const struct kvm_memory_slot *free,
> }
> }
>
> +unsigned long kvmppc_h_svm_init_abort(struct kvm *kvm)
> +{
> + int i;
> +
> + if (!(kvm->arch.secure_guest & KVMPPC_SECURE_INIT_START))
> + return H_UNSUPPORTED;
It should also return H_UNSUPPORTED when
(kvm->arch.secure_guest & KVMPPC_SECURE_INIT_DONE) is true.
RP
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