[edk2-devel] [RFC PATCH 6/9] OvmfPkg/AmdSev: Don't overwrite mailbox or pagetables
Tobin Feldman-Fitzthum
tobin at linux.ibm.com
Wed Aug 18 21:20:45 UTC 2021
While restoring pages, the MH should avoid overwriting its
pagetables or the mailbox it uses to communicate with the HV.
Signed-off-by: Tobin Feldman-Fitzthum <tobin at linux.ibm.com>
---
.../ConfidentialMigrationDxe.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.c b/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.c
index 34d449fe10..ee1466eb00 100644
--- a/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.c
+++ b/OvmfPkg/AmdSev/ConfidentialMigration/ConfidentialMigrationDxe.c
@@ -109,6 +109,9 @@ EFIAPI
MigrationHandlerMain ()
{
UINT64 MailboxStart;
+ UINT64 MailboxEnd;
+ UINT64 PagetableStart;
+ UINT64 PagetableEnd;
MH_COMMAND_PARAMETERS *Params;
VOID *PageVa;
@@ -118,6 +121,11 @@ MigrationHandlerMain ()
Params = (VOID *)(MailboxStart + UNENC_VIRT_ADDR_BASE);
PageVa = (VOID *)(MailboxStart + UNENC_VIRT_ADDR_BASE + 0x1000);
+ MailboxEnd = MailboxStart + 2 * EFI_PAGE_SIZE;
+
+ PagetableStart = mMigrationHandlerPageTables;
+ PagetableEnd = PagetableStart + 11 * EFI_PAGE_SIZE;
+
DisableInterrupts ();
Params->Go = 0;
@@ -138,7 +146,14 @@ MigrationHandlerMain ()
break;
case MH_FUNC_RESTORE_PAGE:
- CopyMem ((VOID *)Params->Gpa, PageVa, 4096);
+ //
+ // Don't import a page that covers the mailbox or pagetables.
+ //
+ if (!((Params->Gpa >= MailboxStart && Params->Gpa < MailboxEnd) ||
+ (Params->Gpa >= PagetableStart && Params->Gpa < PagetableEnd))) {
+
+ CopyMem ((VOID *)Params->Gpa, PageVa, 4096);
+ }
Params->Ret = MH_SUCCESS;
break;
--
2.20.1
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