On Thu, Nov 11, 2021 at 05:08:47PM +0200, Mika Penttilä wrote:
>
>
> On 11.11.2021 16.13, Chao Peng wrote:
> > Currently support to exit to userspace for private/shared memory
> > conversion.
> >
> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> > Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
> > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> > ---
> > arch/x86/kvm/mmu/mmu.c | 20 ++++++++++++++++++++
> > include/uapi/linux/kvm.h | 15 +++++++++++++++
> > 2 files changed, 35 insertions(+)
> >
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index af5ecf4ef62a..780868888aa8 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -3950,6 +3950,17 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
> > slot = __kvm_vcpu_gfn_to_memslot(vcpu, gfn, private);
> > + /*
> > + * Exit to userspace to map the requested private/shared memory region
> > + * if there is no memslot and (a) the access is private or (b) there is
> > + * an existing private memslot. Emulated MMIO must be accessed through
> > + * shared GPAs, thus a memslot miss on a private GPA is always handled
> > + * as an implicit conversion "request".
> > + */
> > + if (!slot &&
> > + (private || __kvm_vcpu_gfn_to_memslot(vcpu, gfn, true)))
> > + goto out_convert;
> > +
> > /* Don't expose aliases for no slot GFNs or private memslots */
> > if ((cr2_or_gpa & vcpu_gpa_stolen_mask(vcpu)) &&
> > !kvm_is_visible_memslot(slot)) {
> > @@ -3994,6 +4005,15 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
> > *pfn = __gfn_to_pfn_memslot(slot, gfn, false, NULL,
> > write, writable, hva);
> > return false;
> > +
> > +out_convert:
> > + vcpu->run->exit_reason = KVM_EXIT_MEMORY_ERROR;
> > + vcpu->run->mem.type = private ? KVM_EXIT_MEM_MAP_PRIVATE
> > + : KVM_EXIT_MEM_MAP_SHARE;
> > + vcpu->run->mem.u.map.gpa = cr2_or_gpa;
> > + vcpu->run->mem.u.map.size = PAGE_SIZE;
> > + return true;
> > +
> I think this does just retry, no exit to user space?
Good catch, thanks.
Chao
>
>
>
>
> > }
> > static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index 8d20caae9180..470c472a9451 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -233,6 +233,18 @@ struct kvm_xen_exit {
> > } u;
> > };
> > +struct kvm_memory_exit {
> > +#define KVM_EXIT_MEM_MAP_SHARE 1
> > +#define KVM_EXIT_MEM_MAP_PRIVATE 2
> > + __u32 type;
> > + union {
> > + struct {
> > + __u64 gpa;
> > + __u64 size;
> > + } map;
> > + } u;
> > +};
> > +
> > #define KVM_S390_GET_SKEYS_NONE 1
> > #define KVM_S390_SKEYS_MAX 1048576
> > @@ -272,6 +284,7 @@ struct kvm_xen_exit {
> > #define KVM_EXIT_X86_BUS_LOCK 33
> > #define KVM_EXIT_XEN 34
> > #define KVM_EXIT_TDVMCALL 35
> > +#define KVM_EXIT_MEMORY_ERROR 36
> > /* For KVM_EXIT_INTERNAL_ERROR */
> > /* Emulate instruction failed. */
> > @@ -455,6 +468,8 @@ struct kvm_run {
> > __u64 subfunc;
> > __u64 param[4];
> > } tdvmcall;
> > + /* KVM_EXIT_MEMORY_ERROR */
> > + struct kvm_memory_exit mem;
> > /* Fix the size of the union. */
> > char padding[256];
> > };
>
