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 --- arch/arm/lib/putuser.S | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) create mode 100644 arch/arm/lib/putuser.S (limited to 'arch/arm/lib/putuser.S') diff --git a/arch/arm/lib/putuser.S b/arch/arm/lib/putuser.S new file mode 100644 index 000000000..bdd8836dc --- /dev/null +++ b/arch/arm/lib/putuser.S @@ -0,0 +1,95 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/lib/putuser.S + * + * Copyright (C) 2001 Russell King + * + * Idea from x86 version, (C) Copyright 1998 Linus Torvalds + * + * These functions have a non-standard call interface to make + * them more efficient, especially as they return an error + * value in addition to the "real" return value. + * + * __put_user_X + * + * Inputs: r0 contains the address + * r1 contains the address limit, which must be preserved + * r2, r3 contains the value + * Outputs: r0 is the error code + * lr corrupted + * + * No other registers must be altered. (see + * for specific ASM register usage). + * + * Note that ADDR_LIMIT is either 0 or 0xc0000000 + * Note also that it is intended that __put_user_bad is not global. + */ +#include +#include +#include +#include + +ENTRY(__put_user_1) + check_uaccess r0, 1, r1, ip, __put_user_bad +1: TUSER(strb) r2, [r0] + mov r0, #0 + ret lr +ENDPROC(__put_user_1) + +ENTRY(__put_user_2) + check_uaccess r0, 2, r1, ip, __put_user_bad +#if __LINUX_ARM_ARCH__ >= 6 + +2: TUSER(strh) r2, [r0] + +#else + + mov ip, r2, lsr #8 +#ifndef __ARMEB__ +2: TUSER(strb) r2, [r0], #1 +3: TUSER(strb) ip, [r0] +#else +2: TUSER(strb) ip, [r0], #1 +3: TUSER(strb) r2, [r0] +#endif + +#endif /* __LINUX_ARM_ARCH__ >= 6 */ + mov r0, #0 + ret lr +ENDPROC(__put_user_2) + +ENTRY(__put_user_4) + check_uaccess r0, 4, r1, ip, __put_user_bad +4: TUSER(str) r2, [r0] + mov r0, #0 + ret lr +ENDPROC(__put_user_4) + +ENTRY(__put_user_8) + check_uaccess r0, 8, r1, ip, __put_user_bad +#ifdef CONFIG_THUMB2_KERNEL +5: TUSER(str) r2, [r0] +6: TUSER(str) r3, [r0, #4] +#else +5: TUSER(str) r2, [r0], #4 +6: TUSER(str) r3, [r0] +#endif + mov r0, #0 + ret lr +ENDPROC(__put_user_8) + +__put_user_bad: + mov r0, #-EFAULT + ret lr +ENDPROC(__put_user_bad) + +.pushsection __ex_table, "a" + .long 1b, __put_user_bad + .long 2b, __put_user_bad +#if __LINUX_ARM_ARCH__ < 6 + .long 3b, __put_user_bad +#endif + .long 4b, __put_user_bad + .long 5b, __put_user_bad + .long 6b, __put_user_bad +.popsection -- cgit v1.3.1