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From:   "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
To:     Tianyu Lan <Tianyu.Lan@microsoft.com>
CC:     Tianyu Lan <Tianyu.Lan@microsoft.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "hpa@zytor.com" <hpa@zytor.com>, "x86@kernel.org" <x86@kernel.org>,
        "pbonzini@redhat.com" <pbonzini@redhat.com>,
        "rkrcmar@redhat.com" <rkrcmar@redhat.com>,
        "devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "vkuznets@redhat.com" <vkuznets@redhat.com>
Subject: RE: [RFC Patch 1/3] X86/Hyper-V: Add flush
 HvFlushGuestPhysicalAddressSpace hypercall support
Thread-Topic: [RFC Patch 1/3] X86/Hyper-V: Add flush
 HvFlushGuestPhysicalAddressSpace hypercall support
Thread-Index: AQHT++PSJN1Pnr7LskeW1RYFL4KhNqRR3L4g
Date:   Tue, 5 Jun 2018 16:59:11 +0000
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 <20180604090749.489-2-Tianyu.Lan@microsoft.com>
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> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org <linux-kernel-owner@vger.kernel.=
org> On Behalf
> Of Tianyu Lan
> Sent: Monday, June 4, 2018 2:08 AM
> Cc: Tianyu Lan <Tianyu.Lan@microsoft.com>; KY Srinivasan <kys@microsoft.c=
om>; Haiyang
> Zhang <haiyangz@microsoft.com>; Stephen Hemminger <sthemmin@microsoft.com=
>;
> tglx@linutronix.de; mingo@redhat.com; hpa@zytor.com; x86@kernel.org;
> pbonzini@redhat.com; rkrcmar@redhat.com; devel@linuxdriverproject.org; li=
nux-
> kernel@vger.kernel.org; kvm@vger.kernel.org; vkuznets@redhat.com
> Subject: [RFC Patch 1/3] X86/Hyper-V: Add flush HvFlushGuestPhysicalAddre=
ssSpace hypercall
> support
>=20
> Hyper-V provides a pv hypercall HvFlushGuestPhysicalAddressSpace to flush
> nested VM address space mapping in l1 hypervisor and it's to reduce overh=
ead
> of flushing ept tlb among vcpus. This patch is to implement it.
>=20
> Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>
> ---
> diff --git a/arch/x86/hyperv/nested.c b/arch/x86/hyperv/nested.c
> new file mode 100644
> index 000000000000..17f7c288eccc
> --- /dev/null
> +++ b/arch/x86/hyperv/nested.c
> +#include <linux/types.h>
> +#include <asm/hyperv-tlfs.h>
> +#include <asm/mshyperv.h>
> +#include <asm/tlbflush.h>
> +
> +int hyperv_flush_guest_mapping(u64 as)
> +{
> +	struct hv_guest_mapping_flush **flush_pcpu;
> +	struct hv_guest_mapping_flush *flush;
> +	u64 status =3D U64_MAX;

Initializing status to U64_MAX doesn't seem necessary.

> +	unsigned long flags;
> +	int ret =3D -EFAULT;
> +
> +	if (!hv_hypercall_pg)
> +		goto fault;
> +
> +	local_irq_save(flags);
> +
> +	flush_pcpu =3D (struct hv_guest_mapping_flush **)
> +		this_cpu_ptr(hyperv_pcpu_input_arg);
> +
> +	flush =3D *flush_pcpu;
> +
> +	if (unlikely(!flush)) {
> +		local_irq_restore(flags);
> +		goto fault;
> +	}
> +
> +	flush->address_space =3D as;
> +	flush->flags =3D 0;
> +
> +	status =3D hv_do_hypercall(HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE,
> +				 flush, NULL);
> +	local_irq_restore(flags);
> +
> +	if (!(status & HV_HYPERCALL_RESULT_MASK))
> +		ret =3D 0;
> +
> +fault:
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(hyperv_flush_guest_mapping);
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hy=
perv-tlfs.h
> index b8c89265baf0..53bbeb08faea 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -309,6 +309,7 @@ struct ms_hyperv_tsc_page {
>  #define HV_X64_MSR_REENLIGHTENMENT_CONTROL	0x40000106
>=20
>  /* Nested features (CPUID 0x4000000A) EAX */
> +#define HV_X64_NESTED_GUSET_MAPPING_FLUSH	BIT(18)

The #define name is misspelled.  "_GUSET_" should be "_GUEST_".
And the matching usage in patch 3/3 will need to be updated as well.

Michael