From: Tom Lendacky <thomas.lendacky@amd•com>
To: Dexuan Cui <decui@microsoft•com>,
"Michael Kelley (LINUX)" <mikelley@microsoft•com>,
Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@linux•intel.com>,
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Subject: Re: [Patch v3 05/14] x86/mm: Handle decryption/re-encryption of bss_decrypted consistently
Date: Mon, 28 Nov 2022 08:15:58 -0600 [thread overview]
Message-ID: <fbf2cdcc-4ff7-b466-a6af-7a147f3bc94d@amd.com> (raw)
In-Reply-To: <SA1PR21MB133512D4B7B78DB38765EBFEBF139@SA1PR21MB1335.namprd21.prod.outlook.com>
On 11/27/22 20:52, Dexuan Cui wrote:
>> From: Michael Kelley (LINUX) <mikelley@microsoft•com>
>> Sent: Thursday, November 17, 2022 6:56 PM
>> [...]
>>
>> But I had not thought about TDX. In the TDX case, it appears that
>> sme_postprocess_startup() will not decrypt the bss_decrypted section.
>> The corresponding mem_encrypt_free_decrypted_mem() is a no-op unless
>> CONFIG_AMD_MEM_ENCRYPT is set. But maybe if someone builds a
>> kernel image that supports both TDX and AMD encryption, it could break
>> at runtime on a TDX system. I would also note that on a TDX system
>> without CONFIG_AMD_MEM_ENCRYPT, the unused memory in the
>> bss_decrypted section never gets freed.
>
> On a TDX system *with* CONFIG_AMD_MEM_ENCRYPT, the unused
> memory in the bss_decrypted section also never gets freed due to the
> below "return;"
>
> I'd suggest a Fixes tag should be added to make sure the distro vendors
> notice the patch and backport it :-)
>
> BTW, I just posted a similar patch as I didn't notice this patch. I have
> replied to my patch email, asking people to ignore my patch.
>
> Fixes: b3f0907c71e0 ("x86/mm: Add .bss..decrypted section to hold shared variables")
I think the Fixes: tag should really be:
e9d1d2bb75b2 ("treewide: Replace the use of mem_encrypt_active() with cc_platform_has()")
since mem_encrypt_active() used to return sme_me_mask, so the checks were
balanced at that point.
Thanks,
Tom
>
> void __init mem_encrypt_free_decrypted_mem(void)
> {
> unsigned long vaddr, vaddr_end, npages;
> int r;
>
> vaddr = (unsigned long)__start_bss_decrypted_unused;
> vaddr_end = (unsigned long)__end_bss_decrypted;
> npages = (vaddr_end - vaddr) >> PAGE_SHIFT;
>
> /*
> * The unused memory range was mapped decrypted, change the encryption
> * attribute from decrypted to encrypted before freeing it.
> */
> if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
> r = set_memory_encrypted(vaddr, npages);
> if (r) {
> pr_warn("failed to free unused decrypted pages\n");
> return;
> }
> }
>
> free_init_pages("unused decrypted", vaddr, vaddr_end);
> }
>
next prev parent reply other threads:[~2022-11-28 14:16 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 [this message]
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
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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