linux-kernel - Re: [PATCH 11/13] Revert "KVM: x86: add pcommit support"

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Date:	Mon, 6 Jun 2016 09:14:53 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-nvdimm <linux-nvdimm@...1.01.org>,
	Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
	david <david@...morbit.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 11/13] Revert "KVM: x86: add pcommit support"

On Mon, Jun 6, 2016 at 8:14 AM, Paolo Bonzini <pbonzini@...hat.com> wrote:
>
>
> On 04/06/2016 22:53, Dan Williams wrote:
>> This reverts commit 8b3e34e46aca9b6d349b331cd9cf71ccbdc91b2e.
>>
>> Given the deprecation of the pcommit instruction, revert its usage as a
>> vm exit source in kvm.
>>
>> Cc: Xiao Guangrong <guangrong.xiao@...ux.intel.com>
>> Cc: Paolo Bonzini <pbonzini@...hat.com>
>> Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
>> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
>
> This is not what that patch does.  It passes down the pcommit
> instruction to the guest if desired, and lets a nested hypervisor trap
> it (also if desired).  Finally, it lets the guest see the PCOMMIT bit in
> CPUID if the host has it.
>
> If the PCOMMIT cpuid feature is going to stay despite the deprecation,
> I'd prefer to keep this patch.

No, it will be marked as reserved.

> Otherwise please change the commit
> message to
>
> Given the deprecation of the pcommit instruction, the relevant VMX
> features and CPUID bits are not going to be rolled into the SDM.  Remove
> their usage from KVM.

Ok, will do.