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Message-ID: <20221102151836.1310509-1-dionnaglaze@google.com>
Date: Wed, 2 Nov 2022 15:18:32 +0000
From: Dionna Glaze <dionnaglaze@...gle.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org
Cc: Dionna Glaze <dionnaglaze@...gle.com>,
Tom Lendacky <Thomas.Lendacky@....com>,
Paolo Bonzini <pbonzini@...hat.com>,
Joerg Roedel <jroedel@...e.de>,
Peter Gonda <pgonda@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Dave Hansen <dave.hansen@...ux.intel.com>
Subject: [PATCH v5 0/4] Add throttling detection to sev-guest
The guest request synchronous API from SEV-SNP VMs to the host's security
processor consumes a global resource. For this reason, AMD's docs
recommend that the host implements a throttling mechanism. In order for
the guest to know it's been throttled and should try its request again,
we need some good-faith communication from the host that the request
has been throttled.
These patches work with the existing /dev/sev-guest ABI to detect a
throttling code.
Changes from v4:
* Clarified comment on SEV_RET_NO_FW_CALL
* Changed ratelimit loop to use sleep_timeout_interruptible
Changes from v3:
* sev-guest ratelimits itself to one request twice a second.
* Fixed a type signature to use u64 instead of unsigned int
* Set *exitinfo2 unconditionally after the ghcb_hv_call.
Changes from v2:
* Codified the non-firmware-call firmware error code as (u32)-1.
* Changed sev_issue_guest_request unsigned long *fw_err argument to
u64 *exitinfo2 to more accurately and type-safely describe the
value that it outputs.
* Changed sev_issue_guest_request to always set its exitinfo2
argument to either the non-firmware-call error code, the
EXIT_INFO_2 returned from the VMM if the request failed, or 0 on
success. This fixes a bug that returned uninitialized kernel stack
memory to the user when there is no error.
* Changed the throttle behavior to retry in the driver instead of
returning -EAGAIN, due to possible message sequence number reuse
on different message contents.
Changes from v1:
* Changed throttle error code to 2
Cc: Tom Lendacky <Thomas.Lendacky@....com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Joerg Roedel <jroedel@...e.de>
Cc: Peter Gonda <pgonda@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Signed-off-by: Dionna Glaze <dionnaglaze@...gle.com>
Dionna Glaze (4):
ccp: Name -1 return value as SEV_RET_NO_FW_CALL
x86/sev: Change snp_guest_issue_request's fw_err
virt/coco/sev-guest: Remove err in handle_guest_request
virt/coco/sev-guest: interpret VMM errors from guest request
arch/x86/include/asm/sev.h | 4 +-
arch/x86/kernel/sev.c | 10 +++--
drivers/crypto/ccp/sev-dev.c | 2 +-
drivers/virt/coco/sev-guest/sev-guest.c | 57 ++++++++++++++++++++-----
include/uapi/linux/psp-sev.h | 7 +++
include/uapi/linux/sev-guest.h | 18 +++++++-
6 files changed, 78 insertions(+), 20 deletions(-)
--
2.38.1.273.g43a17bfeac-goog
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