[PATCH v6 04/13] x86/mm: Handle decryption/re-encryption of bss_decrypted consistently
From: Michael Kelley <hidden>
Date: 2023-03-09 02:42:00
Also in:
linux-arch, linux-hyperv, linux-iommu, linux-pci, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), x86 mm · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski, Peter Zijlstra
sme_postprocess_startup() decrypts the bss_decrypted section when sme_me_mask is non-zero. mem_encrypt_free_decrypted_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. So check sme_me_mask in mem_encrypt_free_decrypted_mem() too. 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 <redacted> 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..e0b51c0 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_me_mask) { r = set_memory_encrypted(vaddr, npages); if (r) { pr_warn("failed to free unused decrypted pages\n");
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1.8.3.1