Messages in this thread | | | Date | Wed, 2 Nov 2022 15:18:32 +0000 | Subject | [PATCH v5 0/4] Add throttling detection to sev-guest | From | Dionna Glaze <> |
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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@amd.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Joerg Roedel <jroedel@suse.de> Cc: Peter Gonda <pgonda@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Dionna Glaze <dionnaglaze@google.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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