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    Subject[RFC PATCH v2 28/69] KVM: Add per-VM flag to mark read-only memory as unsupported
    Date
    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;

    --
    2.25.1
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