Re: [PATCH v2 2/3] x86/kvm/hyper-v: remove stale entries from vec_bitmap/auto_eoi_bitmap on vector change

Radim Krčmář
2018-03-08T21:08:48Z

2018-03-01 15:15+0100, Vitaly Kuznetsov:
> When a new vector is written to SINx we update vec_bitmap/auto_eoi_bitmap
> but we forget to remove old vector from these masks (in case it is not
> present in some other SINTx).
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
> ---
> arch/x86/include/uapi/asm/hyperv.h | 2 ++
> arch/x86/kvm/hyperv.c | 32 ++++++++++++++++++++++----------
> 2 files changed, 24 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
> index 197c2e6c7376..62c778a303a1 100644
> --- a/arch/x86/include/uapi/asm/hyperv.h
> +++ b/arch/x86/include/uapi/asm/hyperv.h
> @@ -318,6 +318,8 @@ typedef struct _HV_REFERENCE_TSC_PAGE {
> #define HV_SYNIC_SINT_COUNT (16)
> /* Define the expected SynIC version. */
> #define HV_SYNIC_VERSION_1 (0x1)
> +/* Valid SynIC vectors are 16-255. */
> +#define HV_SYNIC_FIRST_VALID_VECTOR (16)
>
> #define HV_SYNIC_CONTROL_ENABLE (1ULL << 0)
> #define HV_SYNIC_SIMP_ENABLE (1ULL << 0)
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index 05f414525538..6d14f808145d 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -74,13 +74,30 @@ static bool synic_has_vector_auto_eoi(struct kvm_vcpu_hv_synic *synic,
> return false;
> }
>
> +static void synic_update_vector(struct kvm_vcpu_hv_synic *synic,
> + int vector)
> +{
> + if (vector < HV_SYNIC_FIRST_VALID_VECTOR)
> + return;
> +
> + if (synic_has_vector_connected(synic, vector))
> + __set_bit(vector, synic->vec_bitmap);
> + else
> + __clear_bit(vector, synic->vec_bitmap);
> +
> + if (synic_has_vector_auto_eoi(synic, vector))
> + __set_bit(vector, synic->auto_eoi_bitmap);
> + else
> + __clear_bit(vector, synic->auto_eoi_bitmap);
> +}
> +
> static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
> u64 data, bool host)
> {
> - int vector;
> + int vector, old_vector;
>
> vector = data & HV_SYNIC_SINT_VECTOR_MASK;
> - if (vector < 16 && !host)
> + if (vector < HV_SYNIC_FIRST_VALID_VECTOR && !host)
> return 1;
> /*
> * Guest may configure multiple SINTs to use the same vector, so
> @@ -88,18 +105,13 @@ static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
> * bitmap of vectors with auto-eoi behavior. The bitmaps are
> * updated here, and atomically queried on fast paths.
> */
> + old_vector = synic_read_sint(synic, sint) & HV_SYNIC_SINT_VECTOR_MASK;
>
> atomic64_set(&synic->sint[sint], data);
>
> - if (synic_has_vector_connected(synic, vector))
> - __set_bit(vector, synic->vec_bitmap);
> - else
> - __clear_bit(vector, synic->vec_bitmap);
> + synic_update_vector(synic, old_vector);
>
> - if (synic_has_vector_auto_eoi(synic, vector))
> - __set_bit(vector, synic->auto_eoi_bitmap);
> - else
> - __clear_bit(vector, synic->auto_eoi_bitmap);
> + synic_update_vector(synic, vector);

This looks like it solves the problem when we get two SINTs with the
same vector back-to-back , but shouldn't these bits really be cleared on
EOI (either auto or manual)?

Thanks.