linux-kernel - RE: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted

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:   Thu, 23 Feb 2023 20:51:49 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Dave Hansen <dave.hansen@...el.com>,
        Sean Christopherson <seanjc@...gle.com>
CC:     Borislav Petkov <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "lpieralisi@...nel.org" <lpieralisi@...nel.org>,
        "robh@...nel.org" <robh@...nel.org>, "kw@...ux.com" <kw@...ux.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "arnd@...db.de" <arnd@...db.de>, "hch@....de" <hch@....de>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "brijesh.singh@....com" <brijesh.singh@....com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "isaku.yamahata@...el.com" <isaku.yamahata@...el.com>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "jane.chu@...cle.com" <jane.chu@...cle.com>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
Subject: RE: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range
 to map as encrypted

From: Dave Hansen <dave.hansen@...el.com> Sent: Thursday, February 23, 2023 12:42 PM
> 
> On 2/23/23 12:26, Dave Hansen wrote:
> >> +       if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
> >> +               /*
> >> +               * Ensure fixmaps for IOAPIC MMIO respect memory encryption pgprot
> >> +               * bits, just like normal ioremap():
> >> +               */
> >> +               if (x86_platform.hyper.is_private_mmio(phys))
> >> +                       flags = pgprot_encrypted(flags);
> >> +               else
> >> +                       flags = pgprot_decrypted(flags);
> >> +       }
> ...
> > It does seem a bit odd that there's a new CC_ATTR_GUEST_MEM_ENCRYPT
> > check wrapping this whole thing.  I guess the trip through
> > pgprot_decrypted() is harmless on normal platforms, though.
> 
> Yeah, that's _really_ odd.  Sean, were you trying to optimize away the
> indirect call or something?
> 
> I would just expect the Hyper-V/vTOM code to leave
> x86_platform.hyper.is_private_mmio alone unless
> it *knows* the platform has private MMIO *and* CC_ATTR_GUEST_MEM_ENCRYPT.

Agreed.

> 
> Is there ever a case where CC_ATTR_GUEST_MEM_ENCRYPT==0 and he
> Hyper-V/vTOM code would need to set x86_platform.hyper.is_private_mmio?

There's no such case. 

I agree that gating with CC_ATTR_GUEST_MEM_ENCRYPT isn't really necessary.
Current upstream code always does the pgprot_decrypted(), and as you said,
that's a no-op on platforms with no memory encryption.

Michael