From 93de2a6a4b91b72607136dd656edf03fb399d27f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2026 09:37:21 -0700 Subject: KVM: SEV: Do cache maintenance on the source VM during intra-host migration Manually perform cache maintenance on the source VM during intra-host migration to ensure no stale data is left in CPU caches after the VM is destroyed. Because the source VM is "converted" to a non-SEV VM, KVM's memory reclaim flows won't trigger cache maintenance, e.g. when all guest memory is reclaimed in response to detaching from the mmu_notifier. Note, relying on the destination VM to do cache maintenance isn't an option as KVM doesn't require identical guest memory configurations, i.e. the source VM may have access to memory that the destination VM does not. Enforcing equivalent memory configurations is infeasible, as it would require a *deep* comparison of memslots, e.g. to verify that not only are the memslot identical, but what the memslots point at is also identical. Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration") Cc: stable@vger.kernel.org Reported-by: Stefan Teodorescu Signed-off-by: Sean Christopherson Message-ID: <20260923163721.1584779-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- drivers/firmware/efi/efibc.c | 92 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) create mode 100644 drivers/firmware/efi/efibc.c (limited to 'drivers/firmware/efi/efibc.c') diff --git a/drivers/firmware/efi/efibc.c b/drivers/firmware/efi/efibc.c new file mode 100644 index 000000000..345a10aa7 --- /dev/null +++ b/drivers/firmware/efi/efibc.c @@ -0,0 +1,92 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * efibc: control EFI bootloaders which obey LoaderEntryOneShot var + * Copyright (c) 2013-2016, Intel Corporation. + */ + +#define pr_fmt(fmt) "efibc: " fmt + +#include +#include +#include +#include +#include + +#define MAX_DATA_LEN 512 + +static int efibc_set_variable(efi_char16_t *name, efi_char16_t *value, + unsigned long len) +{ + efi_status_t status; + + status = efi.set_variable(name, &LINUX_EFI_LOADER_ENTRY_GUID, + EFI_VARIABLE_NON_VOLATILE + | EFI_VARIABLE_BOOTSERVICE_ACCESS + | EFI_VARIABLE_RUNTIME_ACCESS, + len * sizeof(efi_char16_t), value); + + if (status != EFI_SUCCESS) { + pr_err("failed to set EFI variable: 0x%lx\n", status); + return -EIO; + } + return 0; +} + +static int efibc_reboot_notifier_call(struct notifier_block *notifier, + unsigned long event, void *data) +{ + efi_char16_t *reason = event == SYS_RESTART ? L"reboot" + : L"shutdown"; + const u8 *str = data; + efi_char16_t *wdata; + unsigned long l; + int ret; + + ret = efibc_set_variable(L"LoaderEntryRebootReason", reason, + ucs2_strlen(reason)); + if (ret || !data) + return NOTIFY_DONE; + + wdata = kmalloc_objs(efi_char16_t, MAX_DATA_LEN); + if (!wdata) + return NOTIFY_DONE; + + for (l = 0; l < MAX_DATA_LEN - 1 && str[l] != '\0'; l++) + wdata[l] = str[l]; + wdata[l] = L'\0'; + + efibc_set_variable(L"LoaderEntryOneShot", wdata, l); + + kfree(wdata); + return NOTIFY_DONE; +} + +static struct notifier_block efibc_reboot_notifier = { + .notifier_call = efibc_reboot_notifier_call, +}; + +static int __init efibc_init(void) +{ + int ret; + + if (!efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE)) + return -ENODEV; + + ret = register_reboot_notifier(&efibc_reboot_notifier); + if (ret) + pr_err("unable to register reboot notifier\n"); + + return ret; +} +module_init(efibc_init); + +static void __exit efibc_exit(void) +{ + unregister_reboot_notifier(&efibc_reboot_notifier); +} +module_exit(efibc_exit); + +MODULE_AUTHOR("Jeremy Compostella "); +MODULE_AUTHOR("Matt Gumbel