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    SubjectRe: [PATCH v4 0/4] Add throttling detection to sev-guest
    Pinging y'all in case you haven't seen v4 :)

    On Mon, Oct 24, 2022 at 3:47 PM Dionna Glaze <dionnaglaze@google.com> wrote:
    >
    > 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 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 | 61 ++++++++++++++++++++-----
    > include/uapi/linux/psp-sev.h | 7 +++
    > include/uapi/linux/sev-guest.h | 18 +++++++-
    > 6 files changed, 82 insertions(+), 20 deletions(-)
    >
    > --
    > 2.38.0.135.g90850a2211-goog
    >


    --
    -Dionna Glaze, PhD (she/her)

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