From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE267C433FE for ; Thu, 17 Nov 2022 18:12:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240182AbiKQSMi (ORCPT ); Thu, 17 Nov 2022 13:12:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240329AbiKQSLw (ORCPT ); Thu, 17 Nov 2022 13:11:52 -0500 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EF5D682209 for ; Thu, 17 Nov 2022 10:11:50 -0800 (PST) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-370624ca2e8so25923677b3.16 for ; Thu, 17 Nov 2022 10:11:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=wteh+NFEi1GAsB9oF3PCiWMRRI+co3r9IDe7/2rAE34=; b=nMPxbK2ewjH+fsYNZqiLd//2LrKs65SwyM7mNXN787ZD4W6hIOaTT53xBtzBuwe83f dPp8qx9NrhlldMjEFYsXhWxhpArwLywx3EZ5yiRT9eCxLDCW2IyhYOwLtAnlL0wg8slI 8OMjRj6j07oCEOVTquGO1qFYXxy1XvyLgRXhOMv7B/OhbZbgtPsw9gFwd1D7YBQSRH4F EVkBwDdJV5Gzegu0E/MV/fztUe+LBFRAUgq58rdCy767/vUbt02dcLrd0ATI4ibZc3AM 8hluEOAvA6br6+3UyzVP7s6kTDbf78BNguWrUs1opz1P7+su76qBu1ToVn6P8e4UKWH3 /l1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=wteh+NFEi1GAsB9oF3PCiWMRRI+co3r9IDe7/2rAE34=; b=v+tpHOz/IoKJR+jjW3s9DPogzlNab/GHIO4tvreTOJGe7pz8nkLszdiaX5pYpyeoOB mjDuGOTj/zlCU/sgM8VHthiV+H4xwWL00tF6kTRtxY7vBGvRMVqOxQsexM8n8z/xlakj VQHlUFEgYVsZYVG0jR/Fcu2VAZH7TVTqUPaHol84+DBwyjLqOVwRvrCsfQBgcK7I7L1n 7vPBe4cltE9/OnC7TdW+c9YrUBnm2N36fdjzKD2iOZPtVLrprD+Tx1v4/GE/O9XGduR7 44QYnXnQB1mBhK8vpni5JCPULH5hJg113Xn+L+HqC6PjkEmks98pFErHvlHWLsm2RvQZ Jemg== X-Gm-Message-State: ANoB5pnXKptbAo+DvbCVvEXVyjQxcs4vOkcIa4L8wTq+bENPg8IjvWjb pkxmedbLwWnTAHEzN+IM/vsz4XvbM0Xh9eVgOcCAF1XqkGDMJIB3mJs8dyaQA71WMX8+Bt/dW/u IftkB5IWv+NOpto5it0BR6SY6ONARVF3BwUsrAG8HKpt/1a9r2TjeryMDLp5GcKzptYVHCUCXl8 vznS6i12g= X-Google-Smtp-Source: AA0mqf6V5BCoS8nuaZkX6AKXJwgdSPrsb9yINktEj3ef0TIf06GgqLN7xzlorDuSHRHkCtTI+xWz5xk/yNS8Crmgvg== X-Received: from dionnaglaze.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2ee6]) (user=dionnaglaze job=sendgmr) by 2002:a25:74c1:0:b0:6de:47e2:e344 with SMTP id p184-20020a2574c1000000b006de47e2e344mr3355252ybc.450.1668708709870; Thu, 17 Nov 2022 10:11:49 -0800 (PST) Date: Thu, 17 Nov 2022 18:11:27 +0000 In-Reply-To: <20221117181127.1859634-1-dionnaglaze@google.com> Mime-Version: 1.0 References: <20221117181127.1859634-1-dionnaglaze@google.com> X-Mailer: git-send-email 2.38.1.584.g0f3c55d4c2-goog Message-ID: <20221117181127.1859634-3-dionnaglaze@google.com> Subject: [PATCH v2 2/2] kvm: sev: If ccp is busy, report throttled to guest From: Dionna Glaze To: linux-kernel@vger.kernel.org, x86@kernel.org Cc: Dionna Glaze , Thomas Lendacky , Paolo Bonzini , Joerg Roedel , Ingo Molnar , Andy Lutomirsky , John Allen , Herbert Xu , "David S. Miller" , Peter Gonda Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The ccp driver can be overloaded even with 1 HZ throttling. The return value of -EBUSY means that there is no firmware error to report back to user space, so the guest VM would see this as exitinfo2 = 0. The false success can trick the guest to update its the message sequence number when it shouldn't have. Instead, when ccp returns -EBUSY, we report that to userspace as the throttling return value. Cc: Thomas Lendacky Cc: Paolo Bonzini Cc: Joerg Roedel Cc: Ingo Molnar Cc: Andy Lutomirsky Cc: John Allen Cc: Herbert Xu Cc: "David S. Miller" Cc: Peter Gonda Signed-off-by: Dionna Glaze --- arch/x86/kvm/svm/sev.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 3ced06c6e07a..81e4862126fb 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -3335,7 +3335,13 @@ static void snp_handle_guest_request(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t goto unlock; rc = sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &data, &err); - if (rc) + /* + * The ccp driver can return -EBUSY if the PSP is overloaded, so + * we offer that as a throttling signal too. + */ + if (rc == -EBUSY) + rc = SNP_GUEST_REQ_THROTTLED; + else if (rc) /* use the firmware error code */ rc = err; @@ -3368,7 +3374,7 @@ static void snp_handle_ext_guest_request(struct vcpu_svm *svm, gpa_t req_gpa, gp if (snp_throttle_guest_request(sev)) { rc = SNP_GUEST_REQ_THROTTLED; goto e_fail; - } + } data_gpa = vcpu->arch.regs[VCPU_REGS_RAX]; data_npages = vcpu->arch.regs[VCPU_REGS_RBX]; @@ -3392,7 +3398,14 @@ static void snp_handle_ext_guest_request(struct vcpu_svm *svm, gpa_t req_gpa, gp rc = snp_guest_ext_guest_request(&req, (unsigned long)sev->snp_certs_data, &data_npages, &err); - if (rc) { + /* + * The ccp driver can return -EBUSY if the PSP is overloaded, so + * we offer that as a throttling signal too. + */ + if (rc == -EBUSY) { + rc = SNP_GUEST_REQ_THROTTLED; + goto cleanup; + } else if (rc) { /* * If buffer length is small then return the expected * length in rbx. -- 2.38.1.584.g0f3c55d4c2-goog