From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 61EAC28DEEF for ; Thu, 15 May 2025 22:04:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747346660; cv=none; b=dBToX+FHIMrJ8QbWty4PFFdzTzgVFmkAKir3Xl8uV4lIXBDeGzFk5y2Nmmem0k0uf51ArlNOs8Xo53RiBdmrEXB6KaH+HJ+1AcKeVBxJHufj6HXrstk6FdqYyiju3YVCAXQnVIgI13HdQrDwUbd2ZUgzmhQtyOA/4o7+AhShHbQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747346660; c=relaxed/simple; bh=mmLKrWU9BMWCBbc2PskOjz9u++A6Zg7rZw9yObFxywE=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=ddK8RX3sxi4zF9k6MEP+NjJOw7bI6fx6sqavp91Y6ki3huuAFxDfUWq/HMnZwLzMJIKRtNBIVAUQO/DHdVcYkG6BkOofjnJZ2C4wpmrOhj8KiHtYCHLEue5IhiNX09IuWwxggxRwI1I7LCu9pNSF/Paj/XW8jPfh0V3KjSY1EMU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--dionnaglaze.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=PX+fnWIN; arc=none smtp.client-ip=209.85.214.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--dionnaglaze.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="PX+fnWIN" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-22e816139b8so12415355ad.3 for ; Thu, 15 May 2025 15:04:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1747346658; x=1747951458; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=da2OQuvEUljiX7sOqbLfJ1kNKJczIhzC2yFs3FB784s=; b=PX+fnWIN3U99SnP2YbY6QK+x80N1QqXkdUjsmMWg18O48j1Tv+knpGZhdVSW5tQIZs EFt29EC8NR1ZDLmm4MmxLX4uBO29Ir59uQB5QN9Aq6u4cHaAFlj1YIF9UnLma/o49P/b oM0ZSY++UVbvKoN3YYpIzJWE3MRvOosvwDOa6gLnKjBAx+dj9mqwwyV/DGRv92by2Z4I uOXkmETFxF+RaGUVYR7yqCIbBM7xFuUi0USaqMddLyEUVpomwyHRQOpu93w9dqQs/r5y fOSCWAMPamB/WAOZHrvxeptATD5mx3hsPpMEOg44ntaYobsQ6zufSb0+/1Iv3/DZOUdO 2k3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747346658; x=1747951458; 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=da2OQuvEUljiX7sOqbLfJ1kNKJczIhzC2yFs3FB784s=; b=D6LspGob46prMIjMhKuDI1AtIuEf8EPZrFU5kh63LghkKlHgRWbSo+g6DeGql4uTjB 1nWfC7sasJc6rl7cF6plbS5nJI5VTsXGUW2242t3BDKhAQ47+VLqMIA6cX3ysG6FVuK5 Feh77Mugy5svrYKd5Nd4SxwQgy9kM2e0MH3GjFYytvgdbna09ktVhwZPQjNDbzov/E90 69vlRwsOJuMMUzCPS37wOrHf4OxgjUos0M/9KHkbVV15nFcJLqSX1p97YFNa5bsdAd2s XU42orI/nSfKd4AdhuAJ/b665xiI6mpKpyhrbOzZZ8oxNPACkCY3cL/Oq1VYwy/0Fgql 8imw== X-Gm-Message-State: AOJu0Yx2zL1ULZ/msaa/c8ukwgt3hbjvkzymiKa4VqZ9tEakfp/Nv5Ub UhiuWnYcyRPZNdF/WbBRWm1npSEMgtpIwWtZ69h+LAj5KtV+xgAqaxs8R5U70U5P9QHvYPLGb5o kowX3GBqHKrGRSX7KIRPB8AZmBg== X-Google-Smtp-Source: AGHT+IGlf26I+aKQ0s1+qKRvgDiVtukbmuiTudxffeFLhCnrwEABrd4/+TM3/By71fTsSsPwRSUcRT9wY+f7sv5Vlw== X-Received: from plge2.prod.google.com ([2002:a17:902:cf42:b0:231:c831:9520]) (user=dionnaglaze job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:e787:b0:224:26fd:82e5 with SMTP id d9443c01a7336-231d455d9ddmr12636465ad.48.1747346658529; Thu, 15 May 2025 15:04:18 -0700 (PDT) Date: Thu, 15 May 2025 22:04:00 +0000 In-Reply-To: <20250515220400.1096945-1-dionnaglaze@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250515220400.1096945-1-dionnaglaze@google.com> X-Mailer: git-send-email 2.49.0.1101.gccaa498523-goog Message-ID: <20250515220400.1096945-3-dionnaglaze@google.com> Subject: [PATCH v5 2/2] kvm: sev: If ccp is busy, report busy to guest From: Dionna Glaze To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Dionna Glaze , Thomas Lendacky , Paolo Bonzini , Joerg Roedel , Peter Gonda , Borislav Petkov , Sean Christopherson Content-Type: text/plain; charset="UTF-8" The ccp driver can be overloaded even with guest request rate limits. 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 message sequence number when it shouldn't have. Instead, when ccp returns -EBUSY, that is reported to userspace as the throttling return value. Cc: Thomas Lendacky Cc: Paolo Bonzini Cc: Joerg Roedel Cc: Peter Gonda Cc: Borislav Petkov Cc: Sean Christopherson Signed-off-by: Dionna Glaze --- arch/x86/kvm/svm/sev.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 35b04a10ed73..884ab3f54fca 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -4063,6 +4063,11 @@ static int snp_handle_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_ * the PSP is dead and commands are timing out. */ ret = sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &data, &fw_err); + if (ret == -EBUSY) { + svm_vmgexit_no_action(svm, SNP_GUEST_ERR(SNP_GUEST_VMM_ERR_BUSY, fw_err)); + ret = 1; + goto out_unlock; + } if (ret && !fw_err) goto out_unlock; -- 2.49.0.1101.gccaa498523-goog