From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Lai Jiangshan <laijs@linux.alibaba.com>,
Yu Zhang <yu.c.zhang@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RFC PATCH 1/2] kvm/x86: intercept guest changes to X86_CR4_LA57
Date: Mon, 28 Sep 2020 09:24:17 -0700 [thread overview]
Message-ID: <20200928162417.GA28825@linux.intel.com> (raw)
In-Reply-To: <20200928083047.3349-1-jiangshanlai@gmail.com>
On Mon, Sep 28, 2020 at 04:30:46PM +0800, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@linux.alibaba.com>
>
> When shadowpaping is enabled, guest should not be allowed
> to toggle X86_CR4_LA57. And X86_CR4_LA57 is a rarely changed
> bit, so we can just intercept all the attempts to toggle it
> no matter shadowpaping is in used or not.
>
> Fixes: fd8cb433734ee ("KVM: MMU: Expose the LA57 feature to VM.")
> Cc: Sean Christopherson <sean.j.christopherson@intel.com>
> Cc: Yu Zhang <yu.c.zhang@linux.intel.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
> ---
> No test to toggle X86_CR4_LA57 in guest since I can't access to
> any CPU supports it. Maybe it is not a real problem.
LA57 doesn't need to be intercepted. It can't be toggled in 64-bit mode
(causes a #GP), and it's ignored in 32-bit mode. That means LA57 can only
take effect when 64-bit mode is enabled, at which time KVM will update its
MMU context accordingly.
> arch/x86/kvm/kvm_cache_regs.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/kvm_cache_regs.h b/arch/x86/kvm/kvm_cache_regs.h
> index cfe83d4ae625..ca0781b41df9 100644
> --- a/arch/x86/kvm/kvm_cache_regs.h
> +++ b/arch/x86/kvm/kvm_cache_regs.h
> @@ -7,7 +7,7 @@
> #define KVM_POSSIBLE_CR0_GUEST_BITS X86_CR0_TS
> #define KVM_POSSIBLE_CR4_GUEST_BITS \
> (X86_CR4_PVI | X86_CR4_DE | X86_CR4_PCE | X86_CR4_OSFXSR \
> - | X86_CR4_OSXMMEXCPT | X86_CR4_LA57 | X86_CR4_PGE | X86_CR4_TSD)
> + | X86_CR4_OSXMMEXCPT | X86_CR4_PGE | X86_CR4_TSD)
>
> #define BUILD_KVM_GPR_ACCESSORS(lname, uname) \
> static __always_inline unsigned long kvm_##lname##_read(struct kvm_vcpu *vcpu)\
> --
> 2.19.1.6.gb485710b
>
next prev parent reply other threads:[~2020-09-28 16:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-28 8:30 [RFC PATCH 1/2] kvm/x86: intercept guest changes to X86_CR4_LA57 Lai Jiangshan
2020-09-28 8:30 ` [RFC PATCH 2/2] kvm/x86: allow guest to toggle X86_CR4_FSGSBASE Lai Jiangshan
2020-09-28 16:24 ` Sean Christopherson [this message]
2020-09-29 5:32 ` [RFC PATCH 1/2] kvm/x86: intercept guest changes to X86_CR4_LA57 Lai Jiangshan
2020-09-29 8:32 ` Sean Christopherson
2020-09-29 8:45 ` Lai Jiangshan
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=20200928162417.GA28825@linux.intel.com \
--to=sean.j.christopherson@intel.com \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=jiangshanlai@gmail.com \
--cc=jmattson@google.com \
--cc=joro@8bytes.org \
--cc=kvm@vger.kernel.org \
--cc=laijs@linux.alibaba.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=tglx@linutronix.de \
--cc=vkuznets@redhat.com \
--cc=wanpengli@tencent.com \
--cc=x86@kernel.org \
--cc=yu.c.zhang@linux.intel.com \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.