lkml.org 
[lkml]   [2023]   [Jan]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH RFC v7 03/64] KVM: SVM: Advertise private memory support to KVM
    On Wed, Jan 04, 2023 at 08:14:19PM -0600, Michael Roth wrote:
    > On Fri, Dec 23, 2022 at 05:56:50PM +0100, Borislav Petkov wrote:
    > > On Wed, Dec 14, 2022 at 01:39:55PM -0600, Michael Roth wrote:
    > > > + bool (*private_mem_enabled)(struct kvm *kvm);
    > >
    > > This looks like a function returning boolean to me. IOW, you can
    > > simplify this to:
    >
    > The semantics and existing uses of KVM_X86_OP_OPTIONAL_RET0() gave me the
    > impression it needed to return an integer value, since by default if a
    > platform doesn't implement the op it would "return 0", and so could
    > still be called unconditionally.
    >
    > Maybe that's not actually enforced, by it seems awkward to try to use a
    > bool return instead. At least for KVM_X86_OP_OPTIONAL_RET0().
    >
    > However, we could just use KVM_X86_OP() to declare it so we can cleanly
    > use a function that returns bool, and then we just need to do:
    >
    > bool kvm_arch_has_private_mem(struct kvm *kvm)
    > {
    > if (kvm_x86_ops.private_mem_enabled)
    > return static_call(kvm_x86_private_mem_enabled)(kvm);

    I guess this is missing:

    return false;

    > }
    >
    > instead of relying on default return value. So I'll take that approach
    > and adopt your other suggested changes.
    >
    > ...
    >
    > On a separate topic though, at a high level, this hook is basically a way
    > for platform-specific code to tell generic KVM code that private memslots
    > are supported by overriding the kvm_arch_has_private_mem() weak
    > reference. In this case the AMD platform is using using kvm->arch.upm_mode
    > flag to convey that, which is in turn set by the
    > KVM_CAP_UNMAPPED_PRIVATE_MEMORY introduced in this series.
    >
    > But if, as I suggested in response to your PATCH 2 comments, we drop
    > KVM_CAP_UNAMMPED_PRIVATE_MEMORY in favor of
    > KVM_SET_SUPPORTED_MEMORY_ATTRIBUTES ioctl to enable "UPM mode" in SEV/SNP
    > code, then we need to rethink things a bit, since KVM_SET_MEMORY_ATTRIBUTES
    > in-part relies on kvm_arch_has_private_mem() to determine what flags are
    > supported, whereas SEV/SNP code would be using what was set by
    > KVM_SET_MEMORY_ATTRIBUTES to determine the return value in
    > kvm_arch_has_private_mem().

    Does this mean that internal calls to kvm_vm_set_region_attr() will
    cease to exist, and it will rely for user space to use the ioctl
    properly instead?

    > So, for AMD, the return value of kvm_arch_has_private_mem() needs to rely
    > on something else. Maybe the logic can just be:
    >
    > bool svm_private_mem_enabled(struct kvm *kvm)
    > {
    > return sev_enabled(kvm) || sev_snp_enabled(kvm)
    > }
    >
    > (at least in the context of this patchset where UPM support is added for
    > both SEV and SNP).
    >
    > So I'll plan to make that change as well.
    >
    > -Mike
    >
    > >
    > > diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
    > > index 82ba4a564e58..4449aeff0dff 100644
    > > --- a/arch/x86/include/asm/kvm-x86-ops.h
    > > +++ b/arch/x86/include/asm/kvm-x86-ops.h
    > > @@ -129,6 +129,7 @@ KVM_X86_OP(msr_filter_changed)
    > > KVM_X86_OP(complete_emulated_msr)
    > > KVM_X86_OP(vcpu_deliver_sipi_vector)
    > > KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons);
    > > +KVM_X86_OP_OPTIONAL_RET0(private_mem_enabled);
    > >
    > > #undef KVM_X86_OP
    > > #undef KVM_X86_OP_OPTIONAL
    > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    > > index 1da0474edb2d..1b4b89ddeb55 100644
    > > --- a/arch/x86/include/asm/kvm_host.h
    > > +++ b/arch/x86/include/asm/kvm_host.h
    > > @@ -1574,6 +1574,7 @@ struct kvm_x86_ops {
    > >
    > > void (*load_mmu_pgd)(struct kvm_vcpu *vcpu, hpa_t root_hpa,
    > > int root_level);
    > > + bool (*private_mem_enabled)(struct kvm *kvm);
    > >
    > > bool (*has_wbinvd_exit)(void);
    > >
    > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
    > > index ce362e88a567..73b780fa4653 100644
    > > --- a/arch/x86/kvm/svm/svm.c
    > > +++ b/arch/x86/kvm/svm/svm.c
    > > @@ -4680,6 +4680,14 @@ static int svm_vm_init(struct kvm *kvm)
    > > return 0;
    > > }
    > >
    > > +static bool svm_private_mem_enabled(struct kvm *kvm)
    > > +{
    > > + if (sev_guest(kvm))
    > > + return kvm->arch.upm_mode;
    > > +
    > > + return IS_ENABLED(CONFIG_HAVE_KVM_PRIVATE_MEM_TESTING);
    > > +}
    > > +
    > > static struct kvm_x86_ops svm_x86_ops __initdata = {
    > > .name = "kvm_amd",
    > >
    > > @@ -4760,6 +4768,8 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
    > >
    > > .vcpu_after_set_cpuid = svm_vcpu_after_set_cpuid,
    > >
    > > + .private_mem_enabled = svm_private_mem_enabled,
    > > +
    > > .has_wbinvd_exit = svm_has_wbinvd_exit,
    > >
    > > .get_l2_tsc_offset = svm_get_l2_tsc_offset,
    > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    > > index 823646d601db..9a1ca59d36a4 100644
    > > --- a/arch/x86/kvm/x86.c
    > > +++ b/arch/x86/kvm/x86.c
    > > @@ -12556,6 +12556,11 @@ void __user * __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa,
    > > }
    > > EXPORT_SYMBOL_GPL(__x86_set_memory_region);
    > >
    > > +bool kvm_arch_has_private_mem(struct kvm *kvm)
    > > +{
    > > + return static_call(kvm_x86_private_mem_enabled)(kvm);
    > > +}
    > > +
    > > void kvm_arch_pre_destroy_vm(struct kvm *kvm)
    > > {
    > > kvm_mmu_pre_destroy_vm(kvm);
    > >
    > > --
    > > Regards/Gruss,
    > > Boris.
    > >
    > > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpeople.kernel.org%2Ftglx%2Fnotes-about-netiquette&data=05%7C01%7Cmichael.roth%40amd.com%7C319e89ce555a46eace4d08dae506b51a%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638074114318137471%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=aG11K7va1BhemwlKCKKdcIXEwXGUzImYL%2BZ9%2FQ7XToI%3D&reserved=0

    BR, Jarkko

    \
     
     \ /
      Last update: 2023-03-26 23:51    [W:4.165 / U:0.020 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site