On Tue, Jan 14, 2025 at 08:33:39AM -0600, Tom Lendacky wrote:
On 1/14/25 01:27, Kirill A. Shutemov wrote:
On Mon, Jan 13, 2025 at 02:47:56PM -0600, Tom Lendacky wrote:
On 1/13/25 07:14, Kirill A. Shutemov wrote:
Currently memremap(MEMREMAP_WB) can produce decrypted/shared mapping:
memremap(MEMREMAP_WB) arch_memremap_wb() ioremap_cache() __ioremap_caller(.encrytped = false)
In such cases, the IORES_MAP_ENCRYPTED flag on the memory will determine if the resulting mapping is encrypted or decrypted.
Creating a decrypted mapping without explicit request from the caller is risky:
It can inadvertently expose the guest's data and compromise the guest.
Accessing private memory via shared/decrypted mapping on TDX will either trigger implicit conversion to shared or #VE (depending on VMM implementation).
Implicit conversion is destructive: subsequent access to the same memory via private mapping will trigger a hard-to-debug #VE crash.
The kernel already provides a way to request decrypted mapping explicitly via the MEMREMAP_DEC flag.
Modify memremap(MEMREMAP_WB) to produce encrypted/private mapping by default unless MEMREMAP_DEC is specified.
Fix the crash due to #VE on kexec in TDX guests if CONFIG_EISA is enabled.
This patch causes my bare-metal system to crash during boot when using mem_encrypt=on:
[ 2.392934] efi: memattr: Entry type should be RuntimeServiceCode/Data [ 2.393731] efi: memattr: ! 0x214c42f01f1162a-0xee70ac7bd1a9c629 [type=2028324321|attr=0x6590648fa4209879]
Could you try if this helps?
diff --git a/drivers/firmware/efi/memattr.c b/drivers/firmware/efi/memattr.c index c38b1a335590..b5051dcb7c1d 100644 --- a/drivers/firmware/efi/memattr.c +++ b/drivers/firmware/efi/memattr.c @@ -160,7 +160,7 @@ int __init efi_memattr_apply_permissions(struct mm_struct *mm, if (WARN_ON(!efi_enabled(EFI_MEMMAP))) return 0;
- tbl = memremap(efi_mem_attr_table, tbl_size, MEMREMAP_WB);
- tbl = memremap(efi_mem_attr_table, tbl_size, MEMREMAP_WB | MEMREMAP_DEC);
Well that would work for SME where EFI tables/data are not encrypted, but will break for SEV where EFI tables/data are encrypted.
Hm. Why would it break for SEV? It brings the situation back to what it was before the patch.
Note that that __ioremap_caller() would still check io_desc.flags before mapping it as decrypted.