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From: Sohil Mehta <sohil.mehta@intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: "Chang S. Bae" <chang.seok.bae@intel.com>, <kvm@vger.kernel.org>,
	<x86@kernel.org>, Paolo Bonzini <pbonzini@redhat.com>,
	Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H . Peter Anvin" <hpa@zytor.com>, Shuah Khan <shuah@kernel.org>,
	Binbin Wu <binbin.wu@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Kai Huang <kai.huang@intel.com>,
	Fuad Tabba <fuad.tabba@linux.dev>, Chao Gao <chao.gao@intel.com>,
	Yosry Ahmed <yosry@kernel.org>,
	Claudio Imbrenda <imbrenda@linux.ibm.com>,
	David Matlack <dmatlack@google.com>,
	Bala-Vignesh-Reddy <reddybalavignesh9979@gmail.com>,
	Kishen Maloor <kishen.maloor@intel.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	<linux-kernel@vger.kernel.org>, <linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH v4 4/7] KVM: VMX: Implement LASS violation check
Date: Tue, 15 Sep 2026 17:12:46 -0700	[thread overview]
Message-ID: <f4fdef08-fdf0-4af8-bf59-07c48625b282@intel.com> (raw)
In-Reply-To: <aqlQgQgnLDf2CHqx@google.com>

On 9/15/2026 7:04 AM, Sean Christopherson wrote:
> That said, I love Sohil's idea of adding a function comment.  Someting along the
> lines of "The basic flow is this: <example>, but the actual behavior is far more
> subtle due to many exceptions and edge cases".

Great, how about this?


> /*
>  * Check if an access violates LASS purely based on bit 63 of the linear address
>  * and whether the access targets the "wrong" half of the address space. The
>  * basic flow is straightforward:
>  *
>  *	if (exempt from LASS)
>  *		no violation;
>  *	else if (user access)
>  *		violation when address is in the supervisor half;
>  *	else
>  *		violation when address is in the user half;
>  *
>  * but the actual behavior is far more subtle due to the many exceptions and
>  * edge cases. For example, the implementation depends on which accesses are
>  * exempt, what constitutes a user access, and how supervisor data accesses
>  * differ from instruction fetches.
>  */
> bool vmx_is_lass_violation(struct kvm_vcpu *vcpu, gva_t gva,
> 			   unsigned int size, unsigned int flags)



Sean, other than this, do you want to see any big change in the series?

The sashiko complains are false-positives. There are a couple of nits to
be addressed, and I need to change Binbin's SoBs into Reviewed-bys.
Otherwise, I think the series (1-5) is getting ready to be picked up.


  reply	other threads:[~2026-09-16  0:13 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-06  1:15 [PATCH v4 0/7] KVM: x86: Add LASS virtualization support Sohil Mehta
2026-08-06  1:15 ` [PATCH v4 1/7] KVM: x86: Add an emulator flag to differentiate branch targets from fetches Sohil Mehta
2026-08-06  1:15 ` [PATCH v4 2/7] KVM: x86: Use linear_read_system() to read the TSS I/O bitmap Sohil Mehta
2026-08-19  3:19   ` Binbin Wu
2026-08-19  5:03     ` Sohil Mehta
2026-08-19  5:21       ` H. Peter Anvin
2026-08-19  5:26       ` Binbin Wu
2026-08-06  1:15 ` [PATCH v4 3/7] KVM: x86: Add LASS violation checks during instruction emulation Sohil Mehta
2026-08-19  5:58   ` Binbin Wu
2026-08-06  1:15 ` [PATCH v4 4/7] KVM: VMX: Implement LASS violation check Sohil Mehta
2026-08-19  8:49   ` Binbin Wu
2026-09-14 17:43   ` Chang S. Bae
2026-09-15  5:10     ` Sohil Mehta
2026-09-15 14:04       ` Sean Christopherson
2026-09-16  0:12         ` Sohil Mehta [this message]
2026-09-16 18:38           ` Sean Christopherson
2026-09-16 21:49             ` Sohil Mehta
2026-08-06  1:15 ` [PATCH v4 5/7] KVM: x86: Virtualize LASS and advertise support to userspace Sohil Mehta
2026-08-19  9:01   ` Binbin Wu
2026-08-06  1:15 ` [PATCH v4 6/7] KVM: selftests: Add coverage for LASS CPUID and CR4 handling Sohil Mehta
2026-08-20  6:01   ` Binbin Wu
2026-08-06  1:15 ` [PATCH v4 7/7] selftests/x86: Add a userspace test for LASS enforcement Sohil Mehta
2026-08-20  6:36   ` Binbin Wu
2026-09-15  3:22     ` Sohil Mehta
2026-09-14 18:21   ` Chang S. Bae
2026-09-15  3:16     ` Sohil Mehta
2026-08-26  3:50 ` [PATCH v4 0/7] KVM: x86: Add LASS virtualization support Kishen Maloor
2026-08-27  3:18 ` Chen, Farrah

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