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    SubjectRe: [PATCH 4/4] KVM: hyper-v: Advertise support for fast XMM hypercalls
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    On Thu, Apr 08, 2021 at 03:44:46PM +0000, Wei Liu wrote:
    > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
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    >
    >
    > On Thu, Apr 08, 2021 at 04:20:54PM +0200, Siddharth Chandrasekaran wrote:
    > > On Thu, Apr 08, 2021 at 02:05:53PM +0200, Vitaly Kuznetsov wrote:
    > > > Siddharth Chandrasekaran <sidcha@amazon.de> writes:
    > > >
    > > > > Now that all extant hypercalls that can use XMM registers (based on
    > > > > spec) for input/outputs are patched to support them, we can start
    > > > > advertising this feature to guests.
    > > > >
    > > > > Cc: Alexander Graf <graf@amazon.com>
    > > > > Cc: Evgeny Iakovlev <eyakovl@amazon.de>
    > > > > Signed-off-by: Siddharth Chandrasekaran <sidcha@amazon.de>
    > > > > ---
    > > > > arch/x86/include/asm/hyperv-tlfs.h | 4 ++--
    > > > > arch/x86/kvm/hyperv.c | 1 +
    > > > > 2 files changed, 3 insertions(+), 2 deletions(-)
    > > > >
    > > > > diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
    > > > > index e6cd3fee562b..1f160ef60509 100644
    > > > > --- a/arch/x86/include/asm/hyperv-tlfs.h
    > > > > +++ b/arch/x86/include/asm/hyperv-tlfs.h
    > > > > @@ -49,10 +49,10 @@
    > > > > /* Support for physical CPU dynamic partitioning events is available*/
    > > > > #define HV_X64_CPU_DYNAMIC_PARTITIONING_AVAILABLE BIT(3)
    > > > > /*
    > > > > - * Support for passing hypercall input parameter block via XMM
    > > > > + * Support for passing hypercall input and output parameter block via XMM
    > > > > * registers is available
    > > > > */
    > > > > -#define HV_X64_HYPERCALL_PARAMS_XMM_AVAILABLE BIT(4)
    > > > > +#define HV_X64_HYPERCALL_PARAMS_XMM_AVAILABLE BIT(4) | BIT(15)
    > > >
    > > > TLFS 6.0b states that there are two distinct bits for input and output:
    > > >
    > > > CPUID Leaf 0x40000003.EDX:
    > > > Bit 4: support for passing hypercall input via XMM registers is available.
    > > > Bit 15: support for returning hypercall output via XMM registers is available.
    > > >
    > > > and HV_X64_HYPERCALL_PARAMS_XMM_AVAILABLE is not currently used
    > > > anywhere, I'd suggest we just rename
    > > >
    > > > HV_X64_HYPERCALL_PARAMS_XMM_AVAILABLE to HV_X64_HYPERCALL_XMM_INPUT_AVAILABLE
    > > > and add HV_X64_HYPERCALL_XMM_OUTPUT_AVAILABLE (bit 15).
    > >
    > > That is how I had it initially; but then noticed that we would never
    > > need to use either of them separately. So it seemed like a reasonable
    > > abstraction to put them together.
    > >
    >
    > They are two separate things in TLFS. Please use two macros here.

    Ack, will split them.

    ~ Sid.



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