Message-ID: <e517d9dd-c1a2-92f6-6b4b-c77d9ea47546@intel.com>
Date:   Thu, 23 Feb 2023 12:41:47 -0800
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Subject: Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range
 to map as encrypted
Content-Language: en-US
To:     Sean Christopherson <seanjc@google.com>,
        "Michael Kelley (LINUX)" <mikelley@microsoft.com>
Cc:     Borislav Petkov <bp@alien8.de>, "hpa@zytor.com" <hpa@zytor.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        Dexuan Cui <decui@microsoft.com>,
        "luto@kernel.org" <luto@kernel.org>,
        "peterz@infradead.org" <peterz@infradead.org>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "edumazet@google.com" <edumazet@google.com>,
        "kuba@kernel.org" <kuba@kernel.org>,
        "pabeni@redhat.com" <pabeni@redhat.com>,
        "lpieralisi@kernel.org" <lpieralisi@kernel.org>,
        "robh@kernel.org" <robh@kernel.org>, "kw@linux.com" <kw@linux.com>,
        "bhelgaas@google.com" <bhelgaas@google.com>,
        "arnd@arndb.de" <arnd@arndb.de>, "hch@lst.de" <hch@lst.de>,
        "m.szyprowski@samsung.com" <m.szyprowski@samsung.com>,
        "robin.murphy@arm.com" <robin.murphy@arm.com>,
        "thomas.lendacky@amd.com" <thomas.lendacky@amd.com>,
        "brijesh.singh@amd.com" <brijesh.singh@amd.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        Tianyu Lan <Tianyu.Lan@microsoft.com>,
        "kirill.shutemov@linux.intel.com" <kirill.shutemov@linux.intel.com>,
        "sathyanarayanan.kuppuswamy@linux.intel.com" 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        "ak@linux.intel.com" <ak@linux.intel.com>,
        "isaku.yamahata@intel.com" <isaku.yamahata@intel.com>,
        "dan.j.williams@intel.com" <dan.j.williams@intel.com>,
        "jane.chu@oracle.com" <jane.chu@oracle.com>,
        "tony.luck@intel.com" <tony.luck@intel.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        "iommu@lists.linux.dev" <iommu@lists.linux.dev>
References: <4216dea6-d899-aecb-2207-caa2ae7db0e3@intel.com>
 <BYAPR21MB16886D92828BA2CA8D47FEA4D7D99@BYAPR21MB1688.namprd21.prod.outlook.com>
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 <Y+aczIbbQm/ZNunZ@zn.tnic> <cb80e102-4b78-1a03-9c32-6450311c0f55@intel.com>
 <Y+auMQ88In7NEc30@google.com> <Y+av0SVUHBLCVdWE@google.com>
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 <Y+bXjxUtSf71E5SS@google.com>
 <e15a1d20-5014-d704-d747-01069b5f4c88@intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <e15a1d20-5014-d704-d747-01069b5f4c88@intel.com>
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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.

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?