From: Tianyu Lan <ltykernel@gmail.com>
To: Michael Kelley <mikelley@microsoft.com>,
hpa@zytor.com, kys@microsoft.com, haiyangz@microsoft.com,
wei.liu@kernel.org, decui@microsoft.com, luto@kernel.org,
peterz@infradead.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, lpieralisi@kernel.org,
robh@kernel.org, kw@linux.com, bhelgaas@google.com,
arnd@arndb.de, hch@infradead.org, m.szyprowski@samsung.com,
robin.murphy@arm.com, thomas.lendacky@amd.com,
brijesh.singh@amd.com, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, dave.hansen@linux.intel.com,
Tianyu.Lan@microsoft.com, kirill.shutemov@linux.intel.com,
sathyanarayanan.kuppuswamy@linux.intel.com, ak@linux.intel.com,
isaku.yamahata@intel.com, dan.j.williams@intel.com,
jane.chu@oracle.com, seanjc@google.com, tony.luck@intel.com,
x86@kernel.org, linux-kernel@vger.kernel.org,
linux-hyperv@vger.kernel.org, netdev@vger.kernel.org,
linux-pci@vger.kernel.org, linux-arch@vger.kernel.org,
iommu@lists.linux.dev
Subject: Re: [Patch v3 07/14] x86/hyperv: Change vTOM handling to use standard coco mechanisms
Date: Thu, 17 Nov 2022 10:59:32 +0800 [thread overview]
Message-ID: <079dc969-37e7-1da0-84cc-9d2e047156d5@gmail.com> (raw)
In-Reply-To: <1668624097-14884-8-git-send-email-mikelley@microsoft.com>
On 11/17/2022 2:41 AM, Michael Kelley wrote:
> Hyper-V guests on AMD SEV-SNP hardware have the option of using the
> "virtual Top Of Memory" (vTOM) feature specified by the SEV-SNP
> architecture. With vTOM, shared vs. private memory accesses are
> controlled by splitting the guest physical address space into two
> halves. vTOM is the dividing line where the uppermost bit of the
> physical address space is set; e.g., with 47 bits of guest physical
> address space, vTOM is 0x40000000000 (bit 46 is set). Guest phyiscal
> memory is accessible at two parallel physical addresses -- one below
> vTOM and one above vTOM. Accesses below vTOM are private (encrypted)
> while accesses above vTOM are shared (decrypted). In this sense, vTOM
> is like the GPA.SHARED bit in Intel TDX.
>
> Support for Hyper-V guests using vTOM was added to the Linux kernel in
> two patch sets[1][2]. This support treats the vTOM bit as part of
> the physical address. For accessing shared (decrypted) memory, these
> patch sets create a second kernel virtual mapping that maps to physical
> addresses above vTOM.
>
> A better approach is to treat the vTOM bit as a protection flag, not
> as part of the physical address. This new approach is like the approach
> for the GPA.SHARED bit in Intel TDX. Rather than creating a second kernel
> virtual mapping, the existing mapping is updated using recently added
> coco mechanisms. When memory is changed between private and shared using
> set_memory_decrypted() and set_memory_encrypted(), the PTEs for the
> existing kernel mapping are changed to add or remove the vTOM bit
> in the guest physical address, just as with TDX. The hypercalls to
> change the memory status on the host side are made using the existing
> callback mechanism. Everything just works, with a minor tweak to map
> the I/O APIC to use private accesses.
>
> To accomplish the switch in approach, the following must be done in
> in this single patch:
>
> * Update Hyper-V initialization to set the cc_mask based on vTOM
> and do other coco initialization.
>
> * Update physical_mask so the vTOM bit is no longer treated as part
> of the physical address
>
> * Update cc_mkenc() and cc_mkdec() to be active for Hyper-V guests.
> This makes the vTOM bit part of the protection flags.
>
> * Code already exists to make hypercalls to inform Hyper-V about pages
> changing between shared and private. Update this code to run as a
> callback from __set_memory_enc_pgtable().
>
> * Remove the Hyper-V special case from __set_memory_enc_dec()
>
> * Remove the Hyper-V specific call to swiotlb_update_mem_attributes()
> since mem_encrypt_init() will now do it.
>
> [1]https://lore.kernel.org/all/20211025122116.264793-1-ltykernel@gmail.com/
> [2]https://lore.kernel.org/all/20211213071407.314309-1-ltykernel@gmail.com/
>
> Signed-off-by: Michael Kelley<mikelley@microsoft.com>
> ---
> arch/x86/coco/core.c | 11 +++++++++-
> arch/x86/hyperv/hv_init.c | 11 ----------
> arch/x86/hyperv/ivm.c | 45 +++++++++++++++++++++++++++++++----------
> arch/x86/include/asm/mshyperv.h | 8 ++------
> arch/x86/kernel/cpu/mshyperv.c | 15 +++++++-------
> arch/x86/mm/pat/set_memory.c | 3 ---
> 6 files changed, 53 insertions(+), 40 deletions(-)
Reviewed-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
next prev parent reply other threads:[~2022-11-17 2:59 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-16 18:41 [Patch v3 00/14] Add PCI pass-thru support to Hyper-V Confidential VMs Michael Kelley
2022-11-16 18:41 ` [Patch v3 01/14] x86/ioremap: Fix page aligned size calculation in __ioremap_caller() Michael Kelley
2022-11-21 13:32 ` Borislav Petkov
2022-11-21 16:40 ` Michael Kelley (LINUX)
2022-11-21 19:45 ` Borislav Petkov
2022-11-21 21:02 ` Michael Kelley (LINUX)
2022-11-21 18:14 ` Dave Hansen
2022-11-21 21:04 ` Michael Kelley (LINUX)
2022-11-21 21:08 ` Borislav Petkov
2022-11-16 18:41 ` [Patch v3 02/14] x86/ioapic: Gate decrypted mapping on cc_platform_has() attribute Michael Kelley
2022-11-17 21:39 ` Sathyanarayanan Kuppuswamy
2022-11-21 13:50 ` Borislav Petkov
2022-11-21 16:43 ` Michael Kelley (LINUX)
2022-11-21 19:47 ` Borislav Petkov
2022-11-16 18:41 ` [Patch v3 03/14] x86/hyperv: Reorder code in prep for subsequent patch Michael Kelley
2022-11-16 18:41 ` [Patch v3 04/14] Drivers: hv: Explicitly request decrypted in vmap_pfn() calls Michael Kelley
2022-11-16 18:41 ` [Patch v3 05/14] x86/mm: Handle decryption/re-encryption of bss_decrypted consistently Michael Kelley
2022-11-16 20:35 ` Tom Lendacky
2022-11-16 21:15 ` Tom Lendacky
2022-11-18 2:59 ` Michael Kelley (LINUX)
2022-11-17 21:47 ` Sathyanarayanan Kuppuswamy
2022-11-18 2:55 ` Michael Kelley (LINUX)
2022-11-21 14:39 ` Borislav Petkov
2022-11-21 22:06 ` Sathyanarayanan Kuppuswamy
2022-11-22 17:59 ` Michael Kelley (LINUX)
2022-11-28 10:50 ` Borislav Petkov
2022-11-28 2:52 ` Dexuan Cui
2022-11-28 14:15 ` Tom Lendacky
2022-11-28 18:06 ` Dexuan Cui
2022-11-21 14:40 ` Borislav Petkov
2022-11-16 18:41 ` [Patch v3 06/14] init: Call mem_encrypt_init() after Hyper-V hypercall init is done Michael Kelley
2022-11-16 21:14 ` Tom Lendacky
2022-11-21 14:46 ` Borislav Petkov
2022-11-16 18:41 ` [Patch v3 07/14] x86/hyperv: Change vTOM handling to use standard coco mechanisms Michael Kelley
2022-11-17 2:59 ` Tianyu Lan [this message]
2022-11-21 15:03 ` Borislav Petkov
2022-11-22 18:22 ` Michael Kelley (LINUX)
2022-11-22 18:30 ` Dave Hansen
2022-11-22 22:02 ` Michael Kelley (LINUX)
2022-11-22 22:18 ` Borislav Petkov
2022-11-23 0:59 ` Michael Kelley (LINUX)
2022-11-28 14:38 ` Michael Kelley (LINUX)
2022-11-28 16:33 ` Borislav Petkov
2022-11-28 16:59 ` Michael Kelley (LINUX)
2022-11-28 17:24 ` Borislav Petkov
2022-11-28 17:55 ` Michael Kelley (LINUX)
2022-11-28 19:56 ` Borislav Petkov
2022-11-29 1:15 ` Michael Kelley (LINUX)
2022-11-29 8:40 ` Borislav Petkov
2022-11-29 15:49 ` Michael Kelley (LINUX)
2022-11-29 17:47 ` Borislav Petkov
2022-11-30 16:11 ` Michael Kelley (LINUX)
2022-11-16 18:41 ` [Patch v3 08/14] swiotlb: Remove bounce buffer remapping for Hyper-V Michael Kelley
2022-11-16 18:41 ` [Patch v3 09/14] Drivers: hv: vmbus: Remove second mapping of VMBus monitor pages Michael Kelley
2022-11-16 18:41 ` [Patch v3 10/14] Drivers: hv: vmbus: Remove second way of mapping ring buffers Michael Kelley
2022-11-16 18:41 ` [Patch v3 11/14] hv_netvsc: Remove second mapping of send and recv buffers Michael Kelley
2022-11-16 18:41 ` [Patch v3 12/14] Drivers: hv: Don't remap addresses that are above shared_gpa_boundary Michael Kelley
2022-11-16 18:41 ` [Patch v3 13/14] PCI: hv: Add hypercalls to read/write MMIO space Michael Kelley
2022-11-17 15:16 ` Wei Liu
2022-11-17 16:14 ` Michael Kelley (LINUX)
2022-11-17 17:01 ` Wei Liu
2022-11-17 16:32 ` Sean Christopherson
2022-11-17 17:00 ` Wei Liu
2022-11-17 18:33 ` Haiyang Zhang
2022-11-18 2:38 ` Michael Kelley (LINUX)
2022-11-16 18:41 ` [Patch v3 14/14] PCI: hv: Enable PCI pass-thru devices in Confidential VMs Michael Kelley
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