From: "Li, Xin3" <xin3.li@intel.com>
To: "Li, Xin3" <xin3.li@intel.com>, "Gao, Chao" <chao.gao@intel.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"linux-kselftest@vger.kernel.org"
<linux-kselftest@vger.kernel.org>,
"seanjc@google.com" <seanjc@google.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"corbet@lwn.net" <corbet@lwn.net>,
"kys@microsoft.com" <kys@microsoft.com>,
"haiyangz@microsoft.com" <haiyangz@microsoft.com>,
"wei.liu@kernel.org" <wei.liu@kernel.org>,
"Cui, Dexuan" <decui@microsoft.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"vkuznets@redhat.com" <vkuznets@redhat.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>
Subject: RE: [PATCH v1 13/23] KVM: VMX: Handle VMX nested exception for FRED
Date: Wed, 6 Dec 2023 08:37:39 +0000 [thread overview]
Message-ID: <SA1PR11MB6734EFF17E15C68AAD12A227A884A@SA1PR11MB6734.namprd11.prod.outlook.com> (raw)
In-Reply-To: <SA1PR11MB67348D3637C2BC6B107C5CCAA8B1A@SA1PR11MB6734.namprd11.prod.outlook.com>
> Subject: RE: [PATCH v1 13/23] KVM: VMX: Handle VMX nested exception for FRED
>
> > >+ if (idt_vectoring_info &
> VECTORING_INFO_DELIVER_CODE_MASK)
> > >+ kvm_requeue_exception_e(vcpu, vector,
> > vmcs_read32(error_code_field),
> > >+ idt_vectoring_info &
> > INTR_INFO_NESTED_EXCEPTION_MASK);
> > >+ else
> > >+ kvm_requeue_exception(vcpu, vector,
> > >+ idt_vectoring_info &
> > INTR_INFO_NESTED_EXCEPTION_MASK);
> >
> > Exiting-event identification can also have bit 13 set, indicating a
> > nested exception encountered and caused VM-exit. when reinjecting the
> > exception to guests, kvm needs to set the "nested" bit, right? I
> > suspect some changes to e.g., handle_exception_nmi() are needed.
>
> The current patch relies on kvm_multiple_exception() to do that. But TBH, I'm
> not sure it can recognize all nested cases. I probably should revisit it.
So the conclusion is that kvm_multiple_exception() is smart enough, and
a VMM doesn't have to check bit 13 of the Exiting-event identification.
In FRED spec 5.0, section 9.2 - New VMX Feature: VMX Nested-Exception
Support, there is a statement at the end of Exiting-event identification:
(The value of this bit is always identical to that of the valid bit of
the original-event identification field.)
It means that even w/o VMX Nested-Exception support, a VMM already knows
if an exception is a nested exception encountered during delivery of
another event in an exception caused VM exit (exit reason 0). This is
done in KVM through reading IDT_VECTORING_INFO_FIELD and calling
vmx_complete_interrupts() immediately after VM exits.
vmx_complete_interrupts() simply queues the original exception if there is
one, and later the nested exception causing the VM exit could be cancelled
if it is a shadow page fault. However if the shadow page fault is caused
by a guest page fault, KVM injects it as a nested exception to have guest
fix its page table.
I will add comments about this background in the next iteration.
next prev parent reply other threads:[~2023-12-06 8:37 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-08 18:29 [PATCH v1 00/23] Enable FRED with KVM VMX Xin Li
2023-11-08 18:29 ` [PATCH v1 01/23] KVM: VMX: Cleanup VMX basic information defines and usages Xin Li
2023-11-08 18:29 ` [PATCH v1 02/23] KVM: VMX: Cleanup VMX misc " Xin Li
2023-11-08 18:29 ` [PATCH v1 03/23] KVM: VMX: Add support for the secondary VM exit controls Xin Li
2023-11-08 18:29 ` [PATCH v1 04/23] KVM: x86: Mark CR4.FRED as not reserved Xin Li
2023-11-08 18:29 ` [PATCH v1 05/23] KVM: VMX: Initialize FRED VM entry/exit controls in vmcs_config Xin Li
2023-11-09 8:53 ` Chao Gao
2023-11-09 15:15 ` Sean Christopherson
2023-11-10 0:04 ` Li, Xin3
2023-11-10 15:01 ` Sean Christopherson
2023-11-14 4:05 ` Li, Xin3
2023-11-13 17:18 ` Nikolay Borisov
2023-11-15 2:39 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 06/23] KVM: VMX: Defer enabling FRED MSRs save/load until after set CPUID Xin Li
2023-11-09 9:15 ` Chao Gao
2023-11-09 23:50 ` Li, Xin3
2023-11-10 0:18 ` Sean Christopherson
2023-11-14 2:50 ` Li, Xin3
2023-11-15 21:47 ` Sean Christopherson
2023-11-08 18:29 ` [PATCH v1 07/23] KVM: VMX: Disable intercepting FRED MSRs Xin Li
2023-11-09 9:21 ` Chao Gao
2023-11-08 18:29 ` [PATCH v1 08/23] KVM: VMX: Initialize VMCS FRED fields Xin Li
2023-11-13 3:04 ` Chao Gao
2023-11-14 6:02 ` Li, Xin3
2023-11-14 6:51 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 09/23] KVM: VMX: Switch FRED RSP0 between host and guest Xin Li
2023-11-13 3:47 ` Chao Gao
2023-11-14 5:17 ` Li, Xin3
2023-11-14 7:47 ` Chao Gao
2023-11-15 3:04 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 10/23] KVM: VMX: Add support for FRED context save/restore Xin Li
2023-11-13 5:24 ` Chao Gao
2023-11-14 4:48 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 11/23] KVM: x86: Add kvm_is_fred_enabled() Xin Li
2023-11-13 7:35 ` Chao Gao
2023-11-14 4:42 ` Li, Xin3
2023-11-14 8:16 ` Chao Gao
2023-11-14 18:57 ` Li, Xin3
2023-11-20 9:04 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 12/23] KVM: VMX: Handle FRED event data Xin Li
2023-11-13 10:14 ` Chao Gao
2023-11-14 4:34 ` Li, Xin3
2023-11-14 8:58 ` Chao Gao
2023-11-15 2:52 ` Li, Xin3
2023-11-16 2:39 ` Chao Gao
2023-11-20 8:16 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 13/23] KVM: VMX: Handle VMX nested exception for FRED Xin Li
2023-11-14 7:40 ` Chao Gao
2023-11-15 3:03 ` Li, Xin3
2023-12-06 8:37 ` Li, Xin3 [this message]
2023-12-07 8:42 ` Chao Gao
2023-12-07 10:09 ` Li, Xin3
2023-12-08 1:56 ` Chao Gao
2023-12-08 23:48 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 14/23] KVM: VMX: Dump FRED context in dump_vmcs() Xin Li
2023-11-14 14:36 ` Nikolay Borisov
2023-11-15 2:41 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 15/23] KVM: nVMX: Add support for the secondary VM exit controls Xin Li
2023-11-09 8:21 ` Jeremi Piotrowski
2023-11-10 0:12 ` Li, Xin3
2023-11-20 15:52 ` Vitaly Kuznetsov
2023-11-20 17:42 ` Li, Xin3
2023-11-08 18:29 ` [PATCH v1 16/23] KVM: nVMX: Add FRED VMCS fields Xin Li
2023-11-08 18:29 ` [PATCH v1 17/23] KVM: nVMX: Add support for VMX FRED controls Xin Li
2023-11-08 18:29 ` [PATCH v1 18/23] KVM: nVMX: Add VMCS FRED states checking Xin Li
2023-11-08 18:29 ` [PATCH v1 19/23] KVM: x86: Allow FRED/LKGS/WRMSRNS to be exposed to guests Xin Li
2023-11-08 18:30 ` [PATCH v1 20/23] KVM: selftests: Add FRED VMCS fields to evmcs Xin Li
2023-11-08 18:30 ` [PATCH v1 21/23] KVM: selftests: Run debug_regs test with FRED enabled Xin Li
2023-11-08 18:30 ` [PATCH v1 22/23] KVM: selftests: Add a new VM guest mode to run user level code Xin Li
2023-11-08 18:30 ` [PATCH v1 23/23] KVM: selftests: Add fred exception tests Xin Li
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=SA1PR11MB6734EFF17E15C68AAD12A227A884A@SA1PR11MB6734.namprd11.prod.outlook.com \
--to=xin3.li@intel.com \
--cc=bp@alien8.de \
--cc=chao.gao@intel.com \
--cc=corbet@lwn.net \
--cc=dave.hansen@linux.intel.com \
--cc=decui@microsoft.com \
--cc=haiyangz@microsoft.com \
--cc=hpa@zytor.com \
--cc=kvm@vger.kernel.org \
--cc=kys@microsoft.com \
--cc=linux-doc@vger.kernel.org \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=ravi.v.shankar@intel.com \
--cc=seanjc@google.com \
--cc=tglx@linutronix.de \
--cc=vkuznets@redhat.com \
--cc=wei.liu@kernel.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).