linux-kernel - [PATCH v4 0/2] kvm: sev: Add SNP guest request throttling

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Message-ID: <20250514184136.238446-1-dionnaglaze@google.com>
Date: Wed, 14 May 2025 18:41:33 +0000
From: Dionna Glaze <dionnaglaze@...gle.com>
To: kvm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, linux-coco@...ts.linux.dev, 
	Dionna Glaze <dionnaglaze@...gle.com>
Subject: [PATCH v4 0/2] kvm: sev: Add SNP guest request throttling

The GHCB specification recommends that SNP guest requests should be
rate limited. Add a command to permit the VMM to set the rate limit
on a per-VM scale.

The AMD-SP is a global resource that must be shared across VMs, so
its time should be multiplexed across VMs fairly. It is the
responsibility of the VMM to ensure all SEV-SNP VMs have a rate limit
set such that the collective set of VMs on the machine have a rate of
access that does not exceed the device's capacity.

The sev-guest device already respects the SNP_GUEST_VMM_ERR_BUSY
result code, so utilize that result to cause the guest to retry after
waiting momentarily.

Changes since v3:
  * Rebased on master, changed module parameter to mem_enc_ioctl
    command. Changed commit descriptions. Much time has passed.
Changes since v2:
  * Rebased on v7, changed "we" wording to passive voice.
Changes since v1:
  * Added missing Ccs to patches.

Dionna Glaze (2):
  kvm: sev: Add SEV-SNP guest request throttling
  kvm: sev: If ccp is busy, report busy to guest

 .../virt/kvm/x86/amd-memory-encryption.rst    | 23 ++++++++++++
 arch/x86/include/uapi/asm/kvm.h               |  7 ++++
 arch/x86/kvm/svm/sev.c                        | 36 +++++++++++++++++++
 arch/x86/kvm/svm/svm.h                        |  2 ++
 4 files changed, 68 insertions(+)

-- 
2.49.0.1045.g170613ef41-goog