| Subject | Re: [RFC PATCH v2 28/69] KVM: Add per-VM flag to mark read-only memory as unsupported | From | Paolo Bonzini <> | Date | Tue, 6 Jul 2021 16:03:09 +0200 |
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On 03/07/21 00:04, isaku.yamahata@intel.com wrote: > From: Isaku Yamahata <isaku.yamahata@intel.com> > > Add a flag for TDX to flag RO memory as unsupported and propagate it to > KVM_MEM_READONLY to allow reporting RO memory as unsupported on a per-VM > basis. TDX1 doesn't expose permission bits to the VMM in the SEPT > tables, i.e. doesn't support read-only private memory. > > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> > Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > --- > arch/x86/kvm/x86.c | 4 +++- > include/linux/kvm_host.h | 4 ++++ > virt/kvm/kvm_main.c | 8 +++++--- > 3 files changed, 12 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index cd9407982366..87212d7563ae 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -3897,7 +3897,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > case KVM_CAP_ASYNC_PF_INT: > case KVM_CAP_GET_TSC_KHZ: > case KVM_CAP_KVMCLOCK_CTRL: > - case KVM_CAP_READONLY_MEM: > case KVM_CAP_HYPERV_TIME: > case KVM_CAP_IOAPIC_POLARITY_IGNORED: > case KVM_CAP_TSC_DEADLINE_TIMER: > @@ -4009,6 +4008,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > if (static_call(kvm_x86_is_vm_type_supported)(KVM_X86_TDX_VM)) > r |= BIT(KVM_X86_TDX_VM); > break; > + case KVM_CAP_READONLY_MEM: > + r = kvm && kvm->readonly_mem_unsupported ? 0 : 1; > + break; > default: > break; > } > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index ddd4d0f68cdf..7ee7104b4b59 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -597,6 +597,10 @@ struct kvm { > unsigned int max_halt_poll_ns; > u32 dirty_ring_size; > > +#ifdef __KVM_HAVE_READONLY_MEM > + bool readonly_mem_unsupported; > +#endif > + > bool vm_bugged; > }; > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 52d40ea75749..63d0c2833913 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1258,12 +1258,14 @@ static void update_memslots(struct kvm_memslots *slots, > } > } > > -static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem) > +static int check_memory_region_flags(struct kvm *kvm, > + const struct kvm_userspace_memory_region *mem) > { > u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES; > > #ifdef __KVM_HAVE_READONLY_MEM > - valid_flags |= KVM_MEM_READONLY; > + if (!kvm->readonly_mem_unsupported) > + valid_flags |= KVM_MEM_READONLY; > #endif > > if (mem->flags & ~valid_flags) > @@ -1436,7 +1438,7 @@ int __kvm_set_memory_region(struct kvm *kvm, > int as_id, id; > int r; > > - r = check_memory_region_flags(mem); > + r = check_memory_region_flags(kvm, mem); > if (r) > return r; > >
For all these flags, which of these limitations will be common to SEV-ES and SEV-SNP (ExtINT injection, MCE injection, changing TSC, read-only memory, dirty logging)? Would it make sense to use vm_type instead of all of them? I guess this also guides the choice of whether to use a single vm-type for TDX and SEV-SNP or two. Probably two is better, and there can be static inline bool functions to derive the support flags from the vm-type.
Paolo
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