Re: [PATCH v3 06/70] kvm: Introduce support for memory_attributes

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Nov 15, 2023 at 02:14:15AM -0500, Xiaoyao Li wrote:
> Introduce the helper functions to set the attributes of a range of
> memory to private or shared.
> 
> This is necessary to notify KVM the private/shared attribute of each gpa
> range. KVM needs the information to decide the GPA needs to be mapped at
> hva-based shared memory or guest_memfd based private memory.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  accel/kvm/kvm-all.c  | 42 ++++++++++++++++++++++++++++++++++++++++++
>  include/sysemu/kvm.h |  3 +++
>  2 files changed, 45 insertions(+)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 69afeb47c9c0..76e2404d54d2 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -102,6 +102,7 @@ bool kvm_has_guest_debug;
>  static int kvm_sstep_flags;
>  static bool kvm_immediate_exit;
>  static bool kvm_guest_memfd_supported;
> +static uint64_t kvm_supported_memory_attributes;
>  static hwaddr kvm_max_slot_size = ~0;
>  
>  static const KVMCapabilityInfo kvm_required_capabilites[] = {
> @@ -1305,6 +1306,44 @@ void kvm_set_max_memslot_size(hwaddr max_slot_size)
>      kvm_max_slot_size = max_slot_size;
>  }
>  
> +static int kvm_set_memory_attributes(hwaddr start, hwaddr size, uint64_t attr)
> +{
> +    struct kvm_memory_attributes attrs;
> +    int r;
> +
> +    attrs.attributes = attr;
> +    attrs.address = start;
> +    attrs.size = size;
> +    attrs.flags = 0;
> +
> +    r = kvm_vm_ioctl(kvm_state, KVM_SET_MEMORY_ATTRIBUTES, &attrs);
> +    if (r) {
> +        warn_report("%s: failed to set memory (0x%lx+%#zx) with attr 0x%lx error '%s'",
> +                     __func__, start, size, attr, strerror(errno));

This is an error condition rather than an warning condition.

Also again I think __func__ is generally not required in an error message,
if the error message text is suitably descriptive - applies to other
patches in this series too.

> +    }
> +    return r;
> +}
> +
> +int kvm_set_memory_attributes_private(hwaddr start, hwaddr size)
> +{
> +    if (!(kvm_supported_memory_attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE)) {
> +        error_report("KVM doesn't support PRIVATE memory attribute\n");
> +        return -EINVAL;
> +    }
> +
> +    return kvm_set_memory_attributes(start, size, KVM_MEMORY_ATTRIBUTE_PRIVATE);
> +}
> +
> +int kvm_set_memory_attributes_shared(hwaddr start, hwaddr size)
> +{
> +    if (!(kvm_supported_memory_attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE)) {
> +        error_report("KVM doesn't support PRIVATE memory attribute\n");
> +        return -EINVAL;
> +    }
> +
> +    return kvm_set_memory_attributes(start, size, 0);
> +}
> +
>  /* Called with KVMMemoryListener.slots_lock held */
>  static void kvm_set_phys_mem(KVMMemoryListener *kml,
>                               MemoryRegionSection *section, bool add)
> @@ -2440,6 +2479,9 @@ static int kvm_init(MachineState *ms)
>  
>      kvm_guest_memfd_supported = kvm_check_extension(s, KVM_CAP_GUEST_MEMFD);
>  
> +    ret = kvm_check_extension(s, KVM_CAP_MEMORY_ATTRIBUTES);
> +    kvm_supported_memory_attributes = ret > 0 ? ret : 0;
> +
>      if (object_property_find(OBJECT(current_machine), "kvm-type")) {
>          g_autofree char *kvm_type = object_property_get_str(OBJECT(current_machine),
>                                                              "kvm-type",
> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> index fedc28c7d17f..0e88958190a4 100644
> --- a/include/sysemu/kvm.h
> +++ b/include/sysemu/kvm.h
> @@ -540,4 +540,7 @@ bool kvm_dirty_ring_enabled(void);
>  uint32_t kvm_dirty_ring_size(void);
>  
>  int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp);
> +
> +int kvm_set_memory_attributes_private(hwaddr start, hwaddr size);
> +int kvm_set_memory_attributes_shared(hwaddr start, hwaddr size);
>  #endif
> -- 
> 2.34.1
> 

With regards,
Daniel
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