[edk2-devel] [PATCH v1 2/2] OvmfPkg/BaseMemEncryptLib: Support to issue unencrypted hypercall
Lendacky, Thomas
thomas.lendacky at amd.com
Wed Dec 2 14:38:23 UTC 2020
On 12/2/20 1:29 AM, Ashish Kalra wrote:
> From: Brijesh Singh <brijesh.singh at amd.com>
>
> By default all the SEV guest memory regions are considered encrypted,
> if a guest changes the encryption attribute of the page (e.g mark a
> page as decrypted) then notify hypervisor. Hypervisor will need to
> track the unencrypted pages. The information will be used during
> guest live migration, guest page migration and guest debugging.
>
> Invoke hypercall via the new hypercall library
>
> This hypercall is used to notify hypervisor when a page is marked as
> 'decrypted' (i.e C-bit removed).
This will miss the SEC GHCB page that is mapped as unencrypted in
OvmfPkg/ResetVector/Ia32/PageTables64.asm. You'll need to remember to mark
that one specifically. I don't think there are any others.
Thanks,
Tom
>
> Cc: Jordan Justen <jordan.l.justen at intel.com>
> Cc: Laszlo Ersek <lersek at redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel at arm.com>
>
> Signed-off-by: Brijesh Singh <brijesh.singh at amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra at amd.com>
> ---
> OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf | 1 +
> OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.c | 18 ++++++++++++++++++
> 2 files changed, 19 insertions(+)
>
> diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf b/OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
> index 7c44d09528..95ee707918 100644
> --- a/OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
> +++ b/OvmfPkg/Library/BaseMemEncryptSevLib/BaseMemEncryptSevLib.inf
> @@ -46,6 +46,7 @@
> DebugLib
> MemoryAllocationLib
> PcdLib
> + MemEncryptHypercallLib
>
> [FeaturePcd]
> gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire
> diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.c
> index 5e110c84ff..1e670b6200 100644
> --- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.c
> +++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/VirtualMemory.c
> @@ -14,6 +14,7 @@
> #include <Library/CpuLib.h>
> #include <Register/Amd/Cpuid.h>
> #include <Register/Cpuid.h>
> +#include <Library/MemEncryptHypercallLib.h>
>
> #include "VirtualMemory.h"
>
> @@ -589,6 +590,9 @@ SetMemoryEncDec (
> UINT64 AddressEncMask;
> BOOLEAN IsWpEnabled;
> RETURN_STATUS Status;
> + UINTN Size;
> + BOOLEAN CBitChanged;
> + PHYSICAL_ADDRESS OrigPhysicalAddress;
>
> //
> // Set PageMapLevel4Entry to suppress incorrect compiler/analyzer warnings.
> @@ -640,6 +644,10 @@ SetMemoryEncDec (
>
> Status = EFI_SUCCESS;
>
> + Size = Length;
> + CBitChanged = FALSE;
> + OrigPhysicalAddress = PhysicalAddress;
> +
> while (Length)
> {
> //
> @@ -699,6 +707,7 @@ SetMemoryEncDec (
> ));
> PhysicalAddress += BIT30;
> Length -= BIT30;
> + CBitChanged = TRUE;
> } else {
> //
> // We must split the page
> @@ -753,6 +762,7 @@ SetMemoryEncDec (
> SetOrClearCBit (&PageDirectory2MEntry->Uint64, Mode);
> PhysicalAddress += BIT21;
> Length -= BIT21;
> + CBitChanged = TRUE;
> } else {
> //
> // We must split up this page into 4K pages
> @@ -795,6 +805,7 @@ SetMemoryEncDec (
> SetOrClearCBit (&PageTableEntry->Uint64, Mode);
> PhysicalAddress += EFI_PAGE_SIZE;
> Length -= EFI_PAGE_SIZE;
> + CBitChanged = TRUE;
> }
> }
> }
> @@ -812,6 +823,13 @@ SetMemoryEncDec (
> //
> CpuFlushTlb();
>
> + //
> + // Notify Hypervisor on C-bit status
> + //
> + if (CBitChanged) {
> + SetMemoryEncDecHypercall3 (OrigPhysicalAddress, EFI_SIZE_TO_PAGES(Size), !Mode);
> + }
> +
> Done:
> //
> // Restore page table write protection, if any.
>
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