From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f49.google.com (mail-lf1-f49.google.com [209.85.167.49]) (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 1281D70 for ; Mon, 12 Jul 2021 18:44:37 +0000 (UTC) Received: by mail-lf1-f49.google.com with SMTP id t17so45290251lfq.0 for ; Mon, 12 Jul 2021 11:44:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=PiEei4/RLF9jTsxsrsUBV60BJotPkybau7lkhBzo5/I=; b=s5pTurZ13T3fHlyrCaThZOVUofr0Cky2/zld5yC8l0myWNX69BvnBNc9Opj6HMkCfc y3CjiuyOByMOeSBVV+o4qu5xJGAw4E/i0pQADCVD/2UOoJrIHi3478hpZZLuoqg1WGst OcCnt2jSO0vJrOopZchNBQ9+MjglGj0qNJPE/zKAtnQq1YJa/gtnDpyh4R1JAsZBUefy UEn4mtsvyV/dfykaoHSxiB9rtcJ7XqsA3Zf+EHYgfdQgNtp/YlSs2jWfDZvn7iwNgCp8 ndBvPbOGbkTvsCYluNITw35znBdI+ATFOMw1rixRW4qkI/Kx/zacoIs85goZ2XGThimw JBFQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=PiEei4/RLF9jTsxsrsUBV60BJotPkybau7lkhBzo5/I=; b=SYrnfFLYSJk5iXSi7Kn9iJcTZ3QXAPzmWjV/iktJdWOjTCjccnQAul+Cy7c1TO/Q6t 7NE3b5wBoRyGsa6HdE7ezlJxezR4rH97Dbv+8fZv3JfcGtYdvXSDItYgFlF4cnFMJITp O6JnvcaGeuIDStgLMWQc7dxFeR/LtNLtw9DQ4ZGVdjQRqKmgk3UOiW7yJ4t/ChWpQtxo jtvBaRdN3cPk5/Vwr+VB3r+qKZ28Vlt4UktRproOwwrTAHWnAGkiny1qsc4GJS7w9Fq8 qtpTo4JXAJosQE1IXOKH+0vW9eEa4ApbsuraxciQKdoGVC+lCA8mnFl5+bh84KkwNkYz +v3Q== X-Gm-Message-State: AOAM531Xe7bso9BNCDpJs+QiXiqyqk1ufh+pXYwQS0LuFYPP00vmu6BX 2719pGheAl2bG4ahtzPm+paracCtrjMzvIByuIUi9A== X-Google-Smtp-Source: ABdhPJw+0tMpJcSV02e9y5OpgohRH2ByLJzW2eRxTjnkHhxkF0WhBTLMKzB5LpXi+sxeGsfF6oUSnjAO+65wVmAaEuA= X-Received: by 2002:ac2:5b1e:: with SMTP id v30mr136916lfn.226.1626115475779; Mon, 12 Jul 2021 11:44:35 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20210707183616.5620-1-brijesh.singh@amd.com> <20210707183616.5620-7-brijesh.singh@amd.com> In-Reply-To: <20210707183616.5620-7-brijesh.singh@amd.com> From: Peter Gonda Date: Mon, 12 Jul 2021 12:44:24 -0600 Message-ID: Subject: Re: [PATCH Part2 RFC v4 06/40] x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction To: Brijesh Singh Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kvm list , linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Joerg Roedel , Tom Lendacky , "H. Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Borislav Petkov , Michael Roth , Vlastimil Babka , tony.luck@intel.com, Nathaniel McCallum , brijesh.ksingh@gmail.com Content-Type: text/plain; charset="UTF-8" > +int psmash(struct page *page) > +{ > + unsigned long spa = page_to_pfn(page) << PAGE_SHIFT; > + int ret; > + > + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP)) > + return -ENXIO; > + > + /* Retry if another processor is modifying the RMP entry. */ > + do { > + /* Binutils version 2.36 supports the PSMASH mnemonic. */ > + asm volatile(".byte 0xF3, 0x0F, 0x01, 0xFF" > + : "=a"(ret) > + : "a"(spa) > + : "memory", "cc"); > + } while (ret == FAIL_INUSE); Should there be some retry limit here for safety? Or do we know that we'll never be stuck in this loop? Ditto for the loop in rmpupdate. > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(psmash); >