Subject: Re: [PATCH v7 5/7] kvmppc: Radix changes for secure guest

From: Bharata B Rao <[email-masked]>
Date: Thu, 29 Aug 2019 13:27:49 +0530

On Wed, Aug 28, 2019 at 08:05:52PM -0700, Sukadev Bhattiprolu wrote:
> > - After the guest becomes secure, when we handle a page fault of a page
> >   belonging to SVM in HV, send that page to UV via UV_PAGE_IN.
> > - Whenever a page is unmapped on the HV side, inform UV via UV_PAGE_INVAL.
> > - Ensure all those routines that walk the secondary page tables of
> >   the guest don't do so in case of secure VM. For secure guest, the
> >   active secondary page tables are in secure memory and the secondary
> >   page tables in HV are freed when guest becomes secure.
> > 
> > Signed-off-by: Bharata B Rao <[email-masked]>
> > ---
> >  arch/powerpc/include/asm/kvm_host.h       | 12 ++++++++++++
> >  arch/powerpc/include/asm/ultravisor-api.h |  1 +
> >  arch/powerpc/include/asm/ultravisor.h     |  5 +++++
> >  arch/powerpc/kvm/book3s_64_mmu_radix.c    | 22 ++++++++++++++++++++++
> >  arch/powerpc/kvm/book3s_hv_devm.c         | 20 ++++++++++++++++++++
> >  5 files changed, 60 insertions(+)
> > 
> > diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> > index 66e5cc8c9759..29333e8de1c4 100644
> > --- a/arch/powerpc/include/asm/kvm_host.h
> > +++ b/arch/powerpc/include/asm/kvm_host.h
> > @@ -867,6 +867,8 @@ static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}
> >  #ifdef CONFIG_PPC_UV
> >  extern int kvmppc_devm_init(void);
> >  extern void kvmppc_devm_free(void);
> > +extern bool kvmppc_is_guest_secure(struct kvm *kvm);
> > +extern int kvmppc_send_page_to_uv(struct kvm *kvm, unsigned long gpa);
> >  #else
> >  static inline int kvmppc_devm_init(void)
> >  {
> > @@ -874,6 +876,16 @@ static inline int kvmppc_devm_init(void)
> >  }
> > 
> >  static inline void kvmppc_devm_free(void) {}
> > +
> > +static inline bool kvmppc_is_guest_secure(struct kvm *kvm)
> > +{
> > +	return false;
> > +}
> > +
> > +static inline int kvmppc_send_page_to_uv(struct kvm *kvm, unsigned long gpa)
> > +{
> > +	return -EFAULT;
> > +}
> >  #endif /* CONFIG_PPC_UV */
> > 
> >  #endif /* __POWERPC_KVM_HOST_H__ */
> > diff --git a/arch/powerpc/include/asm/ultravisor-api.h b/arch/powerpc/include/asm/ultravisor-api.h
> > index 46b1ee381695..cf200d4ce703 100644
> > --- a/arch/powerpc/include/asm/ultravisor-api.h
> > +++ b/arch/powerpc/include/asm/ultravisor-api.h
> > @@ -29,5 +29,6 @@
> >  #define UV_UNREGISTER_MEM_SLOT		0xF124
> >  #define UV_PAGE_IN			0xF128
> >  #define UV_PAGE_OUT			0xF12C
> > +#define UV_PAGE_INVAL			0xF138
> > 
> >  #endif /* _ASM_POWERPC_ULTRAVISOR_API_H */
> > diff --git a/arch/powerpc/include/asm/ultravisor.h b/arch/powerpc/include/asm/ultravisor.h
> > index 719c0c3930b9..b333241bbe4c 100644
> > --- a/arch/powerpc/include/asm/ultravisor.h
> > +++ b/arch/powerpc/include/asm/ultravisor.h
> > @@ -57,4 +57,9 @@ static inline int uv_unregister_mem_slot(u64 lpid, u64 slotid)
> >  	return ucall_norets(UV_UNREGISTER_MEM_SLOT, lpid, slotid);
> >  }
> > 
> > +static inline int uv_page_inval(u64 lpid, u64 gpa, u64 page_shift)
> > +{
> > +	return ucall_norets(UV_PAGE_INVAL, lpid, gpa, page_shift);
> > +}
> > +
> >  #endif	/* _ASM_POWERPC_ULTRAVISOR_H */
> > diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
> > index 2d415c36a61d..93ad34e63045 100644
> > --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
> > +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
> > @@ -19,6 +19,8 @@
> >  #include <asm/pgtable.h>
> >  #include <asm/pgalloc.h>
> >  #include <asm/pte-walk.h>
> > +#include <asm/ultravisor.h>
> > +#include <asm/kvm_host.h>
> > 
> >  /*
> >   * Supported radix tree geometry.
> > @@ -915,6 +917,9 @@ int kvmppc_book3s_radix_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
> >  	if (!(dsisr & DSISR_PRTABLE_FAULT))
> >  		gpa |= ea & 0xfff;
> > 
> > +	if (kvmppc_is_guest_secure(kvm))
> > +		return kvmppc_send_page_to_uv(kvm, gpa & PAGE_MASK);
> > +
> >  	/* Get the corresponding memslot */
> >  	memslot = gfn_to_memslot(kvm, gfn);
> > 
> > @@ -972,6 +977,11 @@ int kvm_unmap_radix(struct kvm *kvm, struct kvm_memory_slot *memslot,
> >  	unsigned long gpa = gfn << PAGE_SHIFT;
> >  	unsigned int shift;
> > 
> > +	if (kvmppc_is_guest_secure(kvm)) {
> > +		uv_page_inval(kvm->arch.lpid, gpa, PAGE_SIZE);
> > +		return 0;
> > +	}
> 
> If it is a page we share with UV, won't we need to drop the HV mapping
> for the page?

I believe we come here via MMU notifies only after dropping HV mapping.

Regards,
Bharata.