linux-kernel - Re: [PATCH Part2 RFC v4 06/40] x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 12 Jul 2021 12:44:24 -0600
From:   Peter Gonda <pgonda@...gle.com>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        kvm list <kvm@...r.kernel.org>, linux-efi@...r.kernel.org,
        platform-driver-x86@...r.kernel.org, linux-coco@...ts.linux.dev,
        linux-mm@...ck.org, linux-crypto@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>, tony.luck@...el.com,
        Nathaniel McCallum <npmccallum@...hat.com>,
        brijesh.ksingh@...il.com
Subject: Re: [PATCH Part2 RFC v4 06/40] x86/sev: Add helper functions for
 RMPUPDATE and PSMASH instruction

> +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);
>