From: Tianyu Lan <Tianyu.Lan@microsoft.com>
To: "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>,
Tianyu Lan <Tianyu.Lan@microsoft.com>
Cc: 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: [PATCH V2 1/5] X86/Hyper-V: Add flush HvFlushGuestPhysicalAddressSpace hypercall support
Date: Wed, 11 Jul 2018 06:01:16 +0000 [thread overview]
Message-ID: <c41ce53f-cf6a-2b0e-4a9c-da01839094c1@microsoft.com> (raw)
In-Reply-To: <SN6PR2101MB11202EAE0D5C623EC0CF8273DC5B0@SN6PR2101MB1120.namprd21.prod.outlook.com>
Hi Michael:
Thanks for your review.
On 7/11/2018 5:29 AM, Michael Kelley (EOSG) wrote:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com> Monday, July 9, 2018 2:03 AM
>> Hyper-V supports a pv hypercall HvFlushGuestPhysicalAddressSpace to
>> flush nested VM address space mapping in l1 hypervisor and it's to
>> reduce overhead of flushing ept tlb among vcpus. This patch is to
>> implement it.
>>
>> Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>
>> ---
>> arch/x86/hyperv/Makefile | 2 +-
>> arch/x86/hyperv/nested.c | 64 ++++++++++++++++++++++++++++++++++++++
>> arch/x86/include/asm/hyperv-tlfs.h | 8 +++++
>> arch/x86/include/asm/mshyperv.h | 2 ++
>> 4 files changed, 75 insertions(+), 1 deletion(-)
>> create mode 100644 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;
>> + unsigned long flags;
>> + int ret = -EFAULT;
>> +
>> + if (!hv_hypercall_pg)
>> + goto fault;
>> +
>> + local_irq_save(flags);
>> +
>> + flush_pcpu = (struct hv_guest_mapping_flush **)
>> + this_cpu_ptr(hyperv_pcpu_input_arg);
>> +
>> + flush = *flush_pcpu;
>> +
>> + if (unlikely(!flush)) {
>> + local_irq_restore(flags);
>> + goto fault;
>> + }
>> +
>> + flush->address_space = as;
>> + flush->flags = 0;
>> +
>> + status = hv_do_hypercall(HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE,
>> + flush, NULL);
>
> Did you consider using a "fast" hypercall? Unless there's some reason I'm
> not aware of, a "fast" hypercall would be perfect here as there are 16 bytes
> of input and no output. Vitaly recently added hv_do_fast_hypercall16()
> in the linux-next tree. See __send_ipi_mask() in hv_apic.c in linux-next
> for an example of usage. With a fast hypercall, you don't need the code for
> getting the per-cpu input arg or the code for local irq save/restore, so the
> code that is left is a lot faster and simpler.
>
> Michael
>
Good suggestion. But the "fast" hypercall still is not available in
kvm-next branch and it's in the x86 tip repo. We may rework this with
"fast" hypercall in the next kernel development cycle if this patchset
is accepted in for 4.19.
>> + local_irq_restore(flags);
>> +
>> + if (!(status & HV_HYPERCALL_RESULT_MASK))
>> + ret = 0;
>> +
>> +fault:
>> + return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(hyperv_flush_guest_mapping);
next prev parent reply other threads:[~2018-07-11 6:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-09 9:02 [PATCH V2 0/5] KVM/x86/hyper-V: Introduce PV guest address space mapping flush support Tianyu Lan
2018-07-09 9:02 ` [PATCH V2 1/5] X86/Hyper-V: Add flush HvFlushGuestPhysicalAddressSpace hypercall support Tianyu Lan
2018-07-10 21:29 ` Michael Kelley (EOSG)
2018-07-11 6:01 ` Tianyu Lan [this message]
2018-07-09 9:02 ` [PATCH V2 2/5] KVM: Add tlb remote flush callback in kvm_x86_ops Tianyu Lan
2018-07-18 11:57 ` Paolo Bonzini
2018-07-18 12:01 ` Paolo Bonzini
2018-07-18 13:25 ` Tianyu Lan
2018-07-09 9:02 ` [PATCH V2 3/5] KVM/VMX: Add identical ept table pointer check Tianyu Lan
2018-07-18 11:59 ` Paolo Bonzini
2018-07-18 13:38 ` Tianyu Lan
2018-07-09 9:02 ` [PATCH V2 4/5] KVM/x86: Add tlb_remote_flush callback support for vmx Tianyu Lan
2018-07-09 9:02 ` [PATCH V2 5/5] X86/Hyper-V: Add hyperv_nested_flush_guest_mapping ftrace support Tianyu Lan
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