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:   Fri, 20 Jan 2023 21:15:10 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     hpa@...or.com, kys@...rosoft.com, haiyangz@...rosoft.com,
        wei.liu@...nel.org, decui@...rosoft.com, luto@...nel.org,
        peterz@...radead.org, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, lpieralisi@...nel.org,
        robh@...nel.org, kw@...ux.com, bhelgaas@...gle.com, arnd@...db.de,
        hch@....de, m.szyprowski@...sung.com, robin.murphy@....com,
        thomas.lendacky@....com, brijesh.singh@....com, tglx@...utronix.de,
        mingo@...hat.com, dave.hansen@...ux.intel.com,
        Tianyu.Lan@...rosoft.com, kirill.shutemov@...ux.intel.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, ak@...ux.intel.com,
        isaku.yamahata@...el.com, dan.j.williams@...el.com,
        jane.chu@...cle.com, seanjc@...gle.com, tony.luck@...el.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org, netdev@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-arch@...r.kernel.org,
        iommu@...ts.linux.dev
Subject: Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range
 to map as encrypted

On Thu, Jan 12, 2023 at 01:42:25PM -0800, Michael Kelley wrote:
> In a AMD SEV-SNP VM using vTOM, devices in MMIO space may be provided by
> the paravisor and need to be mapped as encrypted.  Provide a function
> for the hypervisor to specify the address range for such devices.
> In __ioremap_caller(), map addresses in this range as encrypted.
> 
> Only a single range is supported. If multiple devices need to be
> mapped encrypted, the paravisor must place them within the single
> contiguous range.

This already is starting to sound insufficient and hacky. And it also makes
CC_ATTR_ACCESS_IOAPIC_ENCRYPTED insufficient either.

So, the situation we have is, we're a SEV-SNP VM using vTOM. Which means,
MSR_AMD64_SEV[3] = 1. Or SEV_FEATURES[1], alternatively - same thing.

That MSR cannot be intercepted by the HV and we use it extensively in Linux when
it runs as a SEV-* guest. And I had asked this before, during review, but why
aren't you checking this bit above when you wanna do vTOM-specific work?

Because then you can do that check and

1. map the IO-APIC encrypted
2. map MMIO space of devices from the driver encrypted too
3. ...

and so on.

And you won't need those other, not as nice things...

Hmmm.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette