KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

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 <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 495 insertions, 0 deletions

diff --git a/arch/powerpc/lib/test-code-patching.c b/arch/powerpc/lib/test-code-patching.c
new file mode 100644
index 000000000..1440d9963
--- /dev/null
+++ b/arch/powerpc/lib/test-code-patching.c
@@ -0,0 +1,495 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright 2008 Michael Ellerman, IBM Corporation.
+ */
+
+#include <linux/vmalloc.h>
+#include <linux/init.h>
+
+#include <asm/text-patching.h>
+
+static int __init instr_is_branch_to_addr(const u32 *instr, unsigned long addr)
+{
+	if (instr_is_branch_iform(ppc_inst_read(instr)) ||
+	    instr_is_branch_bform(ppc_inst_read(instr)))
+		return branch_target(instr) == addr;
+
+	return 0;
+}
+
+static void __init test_trampoline(void)
+{
+	asm ("nop;nop;\n");
+}
+
+#define check(x)	do {	\
+	if (!(x))		\
+		pr_err("code-patching: test failed at line %d\n", __LINE__); \
+} while (0)
+
+static void __init test_branch_iform(void)
+{
+	int err;
+	ppc_inst_t instr;
+	u32 tmp[2];
+	u32 *iptr = tmp;
+	unsigned long addr = (unsigned long)tmp;
+
+	/* The simplest case, branch to self, no flags */
+	check(instr_is_branch_iform(ppc_inst(0x48000000)));
+	/* All bits of target set, and flags */
+	check(instr_is_branch_iform(ppc_inst(0x4bffffff)));
+	/* High bit of opcode set, which is wrong */
+	check(!instr_is_branch_iform(ppc_inst(0xcbffffff)));
+	/* Middle bits of opcode set, which is wrong */
+	check(!instr_is_branch_iform(ppc_inst(0x7bffffff)));
+
+	/* Simplest case, branch to self with link */
+	check(instr_is_branch_iform(ppc_inst(0x48000001)));
+	/* All bits of targets set */
+	check(instr_is_branch_iform(ppc_inst(0x4bfffffd)));
+	/* Some bits of targets set */
+	check(instr_is_branch_iform(ppc_inst(0x4bff00fd)));
+	/* Must be a valid branch to start with */
+	check(!instr_is_branch_iform(ppc_inst(0x7bfffffd)));
+
+	/* Absolute branch to 0x100 */
+	ppc_inst_write(iptr, ppc_inst(0x48000103));
+	check(instr_is_branch_to_addr(iptr, 0x100));
+	/* Absolute branch to 0x420fc */
+	ppc_inst_write(iptr, ppc_inst(0x480420ff));
+	check(instr_is_branch_to_addr(iptr, 0x420fc));
+	/* Maximum positive relative branch, + 20MB - 4B */
+	ppc_inst_write(iptr, ppc_inst(0x49fffffc));
+	check(instr_is_branch_to_addr(iptr, addr + 0x1FFFFFC));
+	/* Smallest negative relative branch, - 4B */
+	ppc_inst_write(iptr, ppc_inst(0x4bfffffc));
+	check(instr_is_branch_to_addr(iptr, addr - 4));
+	/* Largest negative relative branch, - 32 MB */
+	ppc_inst_write(iptr, ppc_inst(0x4a000000));
+	check(instr_is_branch_to_addr(iptr, addr - 0x2000000));
+
+	/* Branch to self, with link */
+	err = create_branch(&instr, iptr, addr, BRANCH_SET_LINK);
+	ppc_inst_write(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, addr));
+
+	/* Branch to self - 0x100, with link */
+	err = create_branch(&instr, iptr, addr - 0x100, BRANCH_SET_LINK);
+	ppc_inst_write(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, addr - 0x100));
+
+	/* Branch to self + 0x100, no link */
+	err = create_branch(&instr, iptr, addr + 0x100, 0);
+	ppc_inst_write(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, addr + 0x100));
+
+	/* Maximum relative negative offset, - 32 MB */
+	err = create_branch(&instr, iptr, addr - 0x2000000, BRANCH_SET_LINK);
+	ppc_inst_write(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, addr - 0x2000000));
+
+	/* Out of range relative negative offset, - 32 MB + 4*/
+	err = create_branch(&instr, iptr, addr - 0x2000004, BRANCH_SET_LINK);
+	check(err);
+
+	/* Out of range relative positive offset, + 32 MB */
+	err = create_branch(&instr, iptr, addr + 0x2000000, BRANCH_SET_LINK);
+	check(err);
+
+	/* Unaligned target */
+	err = create_branch(&instr, iptr, addr + 3, BRANCH_SET_LINK);
+	check(err);
+
+	/* Check flags are masked correctly */
+	err = create_branch(&instr, iptr, addr, 0xFFFFFFFC);
+	ppc_inst_write(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, addr));
+	check(ppc_inst_equal(instr, ppc_inst(0x48000000)));
+}
+
+static void __init test_create_function_call(void)
+{
+	u32 *iptr;
+	unsigned long dest;
+	ppc_inst_t instr;
+
+	/* Check we can create a function call */
+	iptr = (u32 *)ppc_function_entry(test_trampoline);
+	dest = ppc_function_entry(test_create_function_call);
+	create_branch(&instr, iptr, dest, BRANCH_SET_LINK);
+	patch_instruction(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, dest));
+}
+
+static void __init test_branch_bform(void)
+{
+	int err;
+	unsigned long addr;
+	ppc_inst_t instr;
+	u32 tmp[2];
+	u32 *iptr = tmp;
+	unsigned int flags;
+
+	addr = (unsigned long)iptr;
+
+	/* The simplest case, branch to self, no flags */
+	check(instr_is_branch_bform(ppc_inst(0x40000000)));
+	/* All bits of target set, and flags */
+	check(instr_is_branch_bform(ppc_inst(0x43ffffff)));
+	/* High bit of opcode set, which is wrong */
+	check(!instr_is_branch_bform(ppc_inst(0xc3ffffff)));
+	/* Middle bits of opcode set, which is wrong */
+	check(!instr_is_branch_bform(ppc_inst(0x7bffffff)));
+
+	/* Absolute conditional branch to 0x100 */
+	ppc_inst_write(iptr, ppc_inst(0x43ff0103));
+	check(instr_is_branch_to_addr(iptr, 0x100));
+	/* Absolute conditional branch to 0x20fc */
+	ppc_inst_write(iptr, ppc_inst(0x43ff20ff));
+	check(instr_is_branch_to_addr(iptr, 0x20fc));
+	/* Maximum positive relative conditional branch, + 32 KB - 4B */
+	ppc_inst_write(iptr, ppc_inst(0x43ff7ffc));
+	check(instr_is_branch_to_addr(iptr, addr + 0x7FFC));
+	/* Smallest negative relative conditional branch, - 4B */
+	ppc_inst_write(iptr, ppc_inst(0x43fffffc));
+	check(instr_is_branch_to_addr(iptr, addr - 4));
+	/* Largest negative relative conditional branch, - 32 KB */
+	ppc_inst_write(iptr, ppc_inst(0x43ff8000));
+	check(instr_is_branch_to_addr(iptr, addr - 0x8000));
+
+	/* All condition code bits set & link */
+	flags = 0x3ff000 | BRANCH_SET_LINK;
+
+	/* Branch to self */
+	err = create_cond_branch(&instr, iptr, addr, flags);
+	ppc_inst_write(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, addr));
+
+	/* Branch to self - 0x100 */
+	err = create_cond_branch(&instr, iptr, addr - 0x100, flags);
+	ppc_inst_write(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, addr - 0x100));
+
+	/* Branch to self + 0x100 */
+	err = create_cond_branch(&instr, iptr, addr + 0x100, flags);
+	ppc_inst_write(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, addr + 0x100));
+
+	/* Maximum relative negative offset, - 32 KB */
+	err = create_cond_branch(&instr, iptr, addr - 0x8000, flags);
+	ppc_inst_write(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, addr - 0x8000));
+
+	/* Out of range relative negative offset, - 32 KB + 4*/
+	err = create_cond_branch(&instr, iptr, addr - 0x8004, flags);
+	check(err);
+
+	/* Out of range relative positive offset, + 32 KB */
+	err = create_cond_branch(&instr, iptr, addr + 0x8000, flags);
+	check(err);
+
+	/* Unaligned target */
+	err = create_cond_branch(&instr, iptr, addr + 3, flags);
+	check(err);
+
+	/* Check flags are masked correctly */
+	err = create_cond_branch(&instr, iptr, addr, 0xFFFFFFFC);
+	ppc_inst_write(iptr, instr);
+	check(instr_is_branch_to_addr(iptr, addr));
+	check(ppc_inst_equal(instr, ppc_inst(0x43FF0000)));
+}
+
+static void __init test_translate_branch(void)
+{
+	unsigned long addr;
+	void *p, *q;
+	ppc_inst_t instr;
+	void *buf;
+
+	buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
+	check(buf);
+	if (!buf)
+		return;
+
+	/* Simple case, branch to self moved a little */
+	p = buf;
+	addr = (unsigned long)p;
+	create_branch(&instr, p, addr, 0);
+	ppc_inst_write(p, instr);
+	check(instr_is_branch_to_addr(p, addr));
+	q = p + 4;
+	translate_branch(&instr, q, p);
+	ppc_inst_write(q, instr);
+	check(instr_is_branch_to_addr(q, addr));
+
+	/* Maximum negative case, move b . to addr + 32 MB */
+	p = buf;
+	addr = (unsigned long)p;
+	create_branch(&instr, p, addr, 0);
+	ppc_inst_write(p, instr);
+	q = buf + 0x2000000;
+	translate_branch(&instr, q, p);
+	ppc_inst_write(q, instr);
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+	check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x4a000000)));
+
+	/* Maximum positive case, move x to x - 32 MB + 4 */
+	p = buf + 0x2000000;
+	addr = (unsigned long)p;
+	create_branch(&instr, p, addr, 0);
+	ppc_inst_write(p, instr);
+	q = buf + 4;
+	translate_branch(&instr, q, p);
+	ppc_inst_write(q, instr);
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+	check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x49fffffc)));
+
+	/* Jump to x + 16 MB moved to x + 20 MB */
+	p = buf;
+	addr = 0x1000000 + (unsigned long)buf;
+	create_branch(&instr, p, addr, BRANCH_SET_LINK);
+	ppc_inst_write(p, instr);
+	q = buf + 0x1400000;
+	translate_branch(&instr, q, p);
+	ppc_inst_write(q, instr);
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+
+	/* Jump to x + 16 MB moved to x - 16 MB + 4 */
+	p = buf + 0x1000000;
+	addr = 0x2000000 + (unsigned long)buf;
+	create_branch(&instr, p, addr, 0);
+	ppc_inst_write(p, instr);
+	q = buf + 4;
+	translate_branch(&instr, q, p);
+	ppc_inst_write(q, instr);
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+
+
+	/* Conditional branch tests */
+
+	/* Simple case, branch to self moved a little */
+	p = buf;
+	addr = (unsigned long)p;
+	create_cond_branch(&instr, p, addr, 0);
+	ppc_inst_write(p, instr);
+	check(instr_is_branch_to_addr(p, addr));
+	q = buf + 4;
+	translate_branch(&instr, q, p);
+	ppc_inst_write(q, instr);
+	check(instr_is_branch_to_addr(q, addr));
+
+	/* Maximum negative case, move b . to addr + 32 KB */
+	p = buf;
+	addr = (unsigned long)p;
+	create_cond_branch(&instr, p, addr, 0xFFFFFFFC);
+	ppc_inst_write(p, instr);
+	q = buf + 0x8000;
+	translate_branch(&instr, q, p);
+	ppc_inst_write(q, instr);
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+	check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x43ff8000)));
+
+	/* Maximum positive case, move x to x - 32 KB + 4 */
+	p = buf + 0x8000;
+	addr = (unsigned long)p;
+	create_cond_branch(&instr, p, addr, 0xFFFFFFFC);
+	ppc_inst_write(p, instr);
+	q = buf + 4;
+	translate_branch(&instr, q, p);
+	ppc_inst_write(q, instr);
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+	check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x43ff7ffc)));
+
+	/* Jump to x + 12 KB moved to x + 20 KB */
+	p = buf;
+	addr = 0x3000 + (unsigned long)buf;
+	create_cond_branch(&instr, p, addr, BRANCH_SET_LINK);
+	ppc_inst_write(p, instr);
+	q = buf + 0x5000;
+	translate_branch(&instr, q, p);
+	ppc_inst_write(q, instr);
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+
+	/* Jump to x + 8 KB moved to x - 8 KB + 4 */
+	p = buf + 0x2000;
+	addr = 0x4000 + (unsigned long)buf;
+	create_cond_branch(&instr, p, addr, 0);
+	ppc_inst_write(p, instr);
+	q = buf + 4;
+	translate_branch(&instr, q, p);
+	ppc_inst_write(q, instr);
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+
+	/* Free the buffer we were using */
+	vfree(buf);
+}
+
+static void __init test_prefixed_patching(void)
+{
+	u32 *iptr = (u32 *)ppc_function_entry(test_trampoline);
+	u32 expected[2] = {OP_PREFIX << 26, 0};
+	ppc_inst_t inst = ppc_inst_prefix(OP_PREFIX << 26, 0);
+
+	if (!IS_ENABLED(CONFIG_PPC64))
+		return;
+
+	patch_instruction(iptr, inst);
+
+	check(!memcmp(iptr, expected, sizeof(expected)));
+}
+
+static void __init test_multi_instruction_patching(void)
+{
+	u32 code[32];
+	void *buf;
+	u32 *addr32;
+	u64 *addr64;
+	ppc_inst_t inst64 = ppc_inst_prefix(OP_PREFIX << 26 | 3UL << 24, PPC_RAW_TRAP());
+	u32 inst32 = PPC_RAW_NOP();
+
+	buf = vzalloc(PAGE_SIZE * 8);
+	check(buf);
+	if (!buf)
+		return;
+
+	/* Test single page 32-bit repeated instruction */
+	addr32 = buf + PAGE_SIZE;
+	check(!patch_instructions(addr32 + 1, &inst32, 12, true));
+
+	check(addr32[0] == 0);
+	check(addr32[1] == inst32);
+	check(addr32[2] == inst32);
+	check(addr32[3] == inst32);
+	check(addr32[4] == 0);
+
+	/* Test single page 64-bit repeated instruction */
+	if (IS_ENABLED(CONFIG_PPC64)) {
+		check(ppc_inst_prefixed(inst64));
+
+		addr64 = buf + PAGE_SIZE * 2;
+		ppc_inst_write(code, inst64);
+		check(!patch_instructions((u32 *)(addr64 + 1), code, 24, true));
+
+		check(addr64[0] == 0);
+		check(ppc_inst_equal(ppc_inst_read((u32 *)&addr64[1]), inst64));
+		check(ppc_inst_equal(ppc_inst_read((u32 *)&addr64[2]), inst64));
+		check(ppc_inst_equal(ppc_inst_read((u32 *)&addr64[3]), inst64));
+		check(addr64[4] == 0);
+	}
+
+	/* Test single page memcpy */
+	addr32 = buf + PAGE_SIZE * 3;
+
+	for (int i = 0; i < ARRAY_SIZE(code); i++)
+		code[i] = i + 1;
+
+	check(!patch_instructions(addr32 + 1, code, sizeof(code), false));
+
+	check(addr32[0] == 0);
+	check(!memcmp(&addr32[1], code, sizeof(code)));
+	check(addr32[ARRAY_SIZE(code) + 1] == 0);
+
+	/* Test multipage 32-bit repeated instruction */
+	addr32 = buf + PAGE_SIZE * 4 - 8;
+	check(!patch_instructions(addr32 + 1, &inst32, 12, true));
+
+	check(addr32[0] == 0);
+	check(addr32[1] == inst32);
+	check(addr32[2] == inst32);
+	check(addr32[3] == inst32);
+	check(addr32[4] == 0);
+
+	/* Test multipage 64-bit repeated instruction */
+	if (IS_ENABLED(CONFIG_PPC64)) {
+		check(ppc_inst_prefixed(inst64));
+
+		addr64 = buf + PAGE_SIZE * 5 - 8;
+		ppc_inst_write(code, inst64);
+		check(!patch_instructions((u32 *)(addr64 + 1), code, 24, true));
+
+		check(addr64[0] == 0);
+		check(ppc_inst_equal(ppc_inst_read((u32 *)&addr64[1]), inst64));
+		check(ppc_inst_equal(ppc_inst_read((u32 *)&addr64[2]), inst64));
+		check(ppc_inst_equal(ppc_inst_read((u32 *)&addr64[3]), inst64));
+		check(addr64[4] == 0);
+	}
+
+	/* Test multipage memcpy */
+	addr32 = buf + PAGE_SIZE * 6 - 12;
+
+	for (int i = 0; i < ARRAY_SIZE(code); i++)
+		code[i] = i + 1;
+
+	check(!patch_instructions(addr32 + 1, code, sizeof(code), false));
+
+	check(addr32[0] == 0);
+	check(!memcmp(&addr32[1], code, sizeof(code)));
+	check(addr32[ARRAY_SIZE(code) + 1] == 0);
+
+	vfree(buf);
+}
+
+static void __init test_data_patching(void)
+{
+	void *buf;
+	u32 *addr32;
+
+	buf = vzalloc(PAGE_SIZE);
+	check(buf);
+	if (!buf)
+		return;
+
+	addr32 = buf + 128;
+
+	addr32[1] = 0xA0A1A2A3;
+	addr32[2] = 0xB0B1B2B3;
+
+	check(!patch_uint(&addr32[1], 0xC0C1C2C3));
+
+	check(addr32[0] == 0);
+	check(addr32[1] == 0xC0C1C2C3);
+	check(addr32[2] == 0xB0B1B2B3);
+	check(addr32[3] == 0);
+
+	/* Unaligned patch_ulong() should fail */
+	if (IS_ENABLED(CONFIG_PPC64))
+		check(patch_ulong(&addr32[1], 0xD0D1D2D3) == -EINVAL);
+
+	check(!patch_ulong(&addr32[2], 0xD0D1D2D3));
+
+	check(addr32[0] == 0);
+	check(addr32[1] == 0xC0C1C2C3);
+	check(*(unsigned long *)(&addr32[2]) == 0xD0D1D2D3);
+
+	if (!IS_ENABLED(CONFIG_PPC64))
+		check(addr32[3] == 0);
+
+	check(addr32[4] == 0);
+
+	vfree(buf);
+}
+
+static int __init test_code_patching(void)
+{
+	pr_info("Running code patching self-tests ...\n");
+
+	test_branch_iform();
+	test_branch_bform();
+	test_create_function_call();
+	test_translate_branch();
+	test_prefixed_patching();
+	test_multi_instruction_patching();
+	test_data_patching();
+
+	return 0;
+}
+late_initcall(test_code_patching);