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From: Peter Zijlstra <peterz@infradead.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jürgen Groß" <jgross@suse.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	virtualization@lists.linux.dev, xin@zytor.com,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Ajay Kaher" <ajay.kaher@broadcom.com>,
	"Alexey Makhalov" <alexey.makhalov@broadcom.com>,
	"Broadcom internal kernel review list"
	<bcm-kernel-feedback-list@broadcom.com>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v2 11/12] x86/paravirt: Don't use pv_ops vector for MSR access functions
Date: Wed, 1 Oct 2025 08:45:43 +0200	[thread overview]
Message-ID: <20251001064543.GM4067720@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <d2c68cbe-2e92-4801-b1a3-af4645e9ba78@zytor.com>

On Tue, Sep 30, 2025 at 12:49:21PM -0700, H. Peter Anvin wrote:

> /* Xen code, stub sets CF = 1 on failure */
> 
>    0:   e8 xx xx xx xx          call   asm_xen_pv_wrmsr
>    5:   73 03                   jnc    0xa
>    7:   0f 0b                   ud2
>    9:   90                      nop
>    a:
> 
> The trap point even ends up in the same place! UD2 can be any 1-, 2-, or
> 3-byte trapping instruction.

Please don't rely on flags to be retained by RET. The various
mitigations have trouble with that.

  parent reply	other threads:[~2025-10-01  6:45 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-09-30  7:03 [PATCH v2 00/12] x86/msr: Inline rdmsr/wrmsr instructions Juergen Gross
2025-09-30  7:03 ` [PATCH v2 01/12] coco/tdx: Rename MSR access helpers Juergen Gross
2025-09-30  9:07   ` Kiryl Shutsemau
2025-09-30  7:03 ` [PATCH v2 02/12] x86/sev: Replace call of native_wrmsr() with native_wrmsrq() Juergen Gross
2025-10-07  6:08   ` Nikunj A Dadhania
2025-09-30  7:03 ` [PATCH v2 03/12] x86/kvm: Remove the KVM private read_msr() function Juergen Gross
2025-09-30 16:04   ` Sean Christopherson
2025-10-01  9:14     ` Jürgen Groß
2025-09-30  7:03 ` [PATCH v2 04/12] x86/msr: Minimize usage of native_*() msr access functions Juergen Gross
2025-09-30  7:03 ` [PATCH v2 05/12] x86/msr: Move MSR trace calls one function level up Juergen Gross
2025-09-30  7:03 ` [PATCH v2 06/12] x86/cpufeatures: Add a CPU feature bit for MSR immediate form instructions Juergen Gross
2025-09-30  7:03 ` [PATCH v2 07/12] x86/opcode: Add immediate form MSR instructions Juergen Gross
2025-09-30  7:03 ` [PATCH v2 08/12] x86/extable: Add support for " Juergen Gross
2025-09-30  8:14   ` Peter Zijlstra
2025-09-30  8:31     ` Jürgen Groß
2025-09-30  7:03 ` [PATCH v2 09/12] x86/msr: Use the alternatives mechanism for WRMSR Juergen Gross
2025-09-30  8:31   ` Peter Zijlstra
2025-09-30  8:46     ` Jürgen Groß
2025-09-30  8:50       ` Peter Zijlstra
2025-09-30 12:51         ` Peter Zijlstra
2025-09-30 15:42           ` Jürgen Groß
2025-10-01  6:43             ` Peter Zijlstra
2025-10-01  7:23               ` Peter Zijlstra
2025-10-03 14:23                 ` Dave Hansen
2025-10-03 16:53                   ` H. Peter Anvin
2025-10-01  8:49       ` Juergen Gross
2025-10-01 10:50         ` Peter Zijlstra
2025-10-01 11:16           ` Jürgen Groß
2025-09-30 16:00   ` Sean Christopherson
2025-10-01  9:13     ` Jürgen Groß
2025-09-30  7:03 ` [PATCH v2 10/12] x86/msr: Use the alternatives mechanism for RDMSR Juergen Gross
2025-09-30  7:03 ` [PATCH v2 11/12] x86/paravirt: Don't use pv_ops vector for MSR access functions Juergen Gross
2025-09-30  8:38   ` Peter Zijlstra
2025-09-30  9:02     ` Jürgen Groß
2025-09-30 10:04       ` Peter Zijlstra
2025-09-30 10:43         ` Jürgen Groß
2025-09-30 19:49           ` H. Peter Anvin
2025-09-30 19:59             ` H. Peter Anvin
2025-10-01  6:45             ` Peter Zijlstra [this message]
2025-09-30 21:27   ` kernel test robot
2025-10-01  5:48     ` Jürgen Groß
2025-09-30  7:03 ` [PATCH v2 12/12] x86/msr: Reduce number of low level MSR access helpers Juergen Gross
2025-09-30 19:19 ` [PATCH v2 00/12] x86/msr: Inline rdmsr/wrmsr instructions H. Peter Anvin

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