Messages in this thread | | | Date | Wed, 16 Nov 2022 15:15:56 -0600 | Subject | Re: [Patch v3 05/14] x86/mm: Handle decryption/re-encryption of bss_decrypted consistently | From | Tom Lendacky <> |
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On 11/16/22 14:35, Tom Lendacky wrote: > On 11/16/22 12:41, Michael Kelley wrote: >> Current code in sme_postprocess_startup() decrypts the bss_decrypted >> section when sme_me_mask is non-zero. But code in >> mem_encrypt_free_decrytped_mem() re-encrypts the unused portion based >> on CC_ATTR_MEM_ENCRYPT. In a Hyper-V guest VM using vTOM, these >> conditions are not equivalent as sme_me_mask is always zero when >> using vTOM. Consequently, mem_encrypt_free_decrypted_mem() attempts >> to re-encrypt memory that was never decrypted. >> >> Fix this in mem_encrypt_free_decrypted_mem() by conditioning the >> re-encryption on the same test for non-zero sme_me_mask. Hyper-V >> guests using vTOM don't need the bss_decrypted section to be >> decrypted, so skipping the decryption/re-encryption doesn't cause >> a problem. >> >> Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Meant to add this in the previous reply...
With the change to use sme_me_mask directly
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
>> --- >> arch/x86/mm/mem_encrypt_amd.c | 10 +++++++--- >> 1 file changed, 7 insertions(+), 3 deletions(-) >> >> diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c >> index 9c4d8db..5a51343 100644 >> --- a/arch/x86/mm/mem_encrypt_amd.c >> +++ b/arch/x86/mm/mem_encrypt_amd.c >> @@ -513,10 +513,14 @@ void __init mem_encrypt_free_decrypted_mem(void) >> 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 the unused memory range was mapped decrypted, change the >> encryption >> + * attribute from decrypted to encrypted before freeing it. Base the >> + * re-encryption on the same condition used for the decryption in >> + * sme_postprocess_startup(). Higher level abstractions, such as >> + * CC_ATTR_MEM_ENCRYPT, aren't necessarily equivalent in a Hyper-V VM >> + * using vTOM, where sme_me_mask is always zero. >> */ >> - if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) { >> + if (sme_get_me_mask()) { > > To be consistent within this file, you should use sme_me_mask directly. > > Thanks, > Tom > >> r = set_memory_encrypted(vaddr, npages); >> if (r) { >> pr_warn("failed to free unused decrypted pages\n");
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