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Re: [PATCH 0/2] x86/svm: Add support for Bus Lock Threshold
- To: Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>
- Date: Tue, 20 Jan 2026 12:22:27 +0100
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- Cc: Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Jason Andryuk <jason.andryuk@xxxxxxx>, "Stefano Stabellini" <sstabellini@xxxxxxxxxx>
- Delivery-date: Tue, 20 Jan 2026 11:22:43 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Tue Jan 20, 2026 at 10:53 AM CET, Alejandro Vallejo wrote:
> Bus Locks are very costly and a VM left unchecked spamming instructions that
> lock the memory bus (e.g: unaligned atomic CAS) makes system perf take a
> nosedive. This patch is similar to BLD of VMX, but for SVM. It configures all
> VMRUNs so they automatically exit at the first encounter of a buslock event,
> effectively rate-limiting them.
Does this warrant an entry in the CHANGELOG?
Cheers,
Alejandro
>
> Cheers,
> Alejandro
>
> Alejandro Vallejo (2):
> x86/svm: Add infrastructure for Bus Lock Threshold
> x86/svm: Intercept Bus Locks for HVM guests
>
> xen/arch/x86/hvm/svm/svm.c | 5 +++++
> xen/arch/x86/hvm/svm/vmcb.c | 6 ++++++
> xen/arch/x86/hvm/svm/vmcb.h | 15 +++++++++++++--
> xen/arch/x86/include/asm/hvm/svm.h | 2 ++
> xen/arch/x86/include/asm/perfc_defn.h | 2 +-
> 5 files changed, 27 insertions(+), 3 deletions(-)
>
>
> base-commit: 7b3e1b4e848d34c9a5b6634009959a7b9dd42104
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