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, 218 insertions, 0 deletions

diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
new file mode 100644
index 000000000..ad9b0430a
--- /dev/null
+++ b/arch/mips/mm/cache.c
@@ -0,0 +1,218 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 1994 - 2003, 06, 07 by Ralf Baechle (ralf@linux-mips.org)
+ * Copyright (C) 2007 MIPS Technologies, Inc.
+ */
+#include <linux/fs.h>
+#include <linux/fcntl.h>
+#include <linux/kernel.h>
+#include <linux/linkage.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/syscalls.h>
+#include <linux/mm.h>
+#include <linux/highmem.h>
+#include <linux/pagemap.h>
+
+#include <asm/bcache.h>
+#include <asm/cacheflush.h>
+#include <asm/processor.h>
+#include <asm/cpu.h>
+#include <asm/cpu-features.h>
+#include <asm/setup.h>
+#include <asm/pgtable.h>
+
+/* Cache operations. */
+void (*flush_cache_all)(void);
+void (*__flush_cache_all)(void);
+EXPORT_SYMBOL_GPL(__flush_cache_all);
+void (*flush_cache_mm)(struct mm_struct *mm);
+void (*flush_cache_range)(struct vm_area_struct *vma, unsigned long start,
+	unsigned long end);
+void (*flush_cache_page)(struct vm_area_struct *vma, unsigned long page,
+	unsigned long pfn);
+void (*flush_icache_range)(unsigned long start, unsigned long end);
+EXPORT_SYMBOL_GPL(flush_icache_range);
+void (*local_flush_icache_range)(unsigned long start, unsigned long end);
+EXPORT_SYMBOL_GPL(local_flush_icache_range);
+void (*__flush_icache_user_range)(unsigned long start, unsigned long end);
+void (*__local_flush_icache_user_range)(unsigned long start, unsigned long end);
+EXPORT_SYMBOL_GPL(__local_flush_icache_user_range);
+
+void (*__flush_cache_vmap)(void);
+void (*__flush_cache_vunmap)(void);
+
+void (*__flush_kernel_vmap_range)(unsigned long vaddr, int size);
+EXPORT_SYMBOL_GPL(__flush_kernel_vmap_range);
+
+/* MIPS specific cache operations */
+void (*flush_data_cache_page)(unsigned long addr);
+void (*flush_icache_all)(void);
+
+EXPORT_SYMBOL(flush_data_cache_page);
+EXPORT_SYMBOL(flush_icache_all);
+
+/*
+ * Dummy cache handling routine
+ */
+
+void cache_noop(void) {}
+
+#ifdef CONFIG_BOARD_SCACHE
+
+static struct bcache_ops no_sc_ops = {
+	.bc_enable = (void *)cache_noop,
+	.bc_disable = (void *)cache_noop,
+	.bc_wback_inv = (void *)cache_noop,
+	.bc_inv = (void *)cache_noop
+};
+
+struct bcache_ops *bcops = &no_sc_ops;
+#endif
+
+#ifdef CONFIG_DMA_NONCOHERENT
+
+/* DMA cache operations. */
+void (*_dma_cache_wback_inv)(unsigned long start, unsigned long size);
+void (*_dma_cache_wback)(unsigned long start, unsigned long size);
+void (*_dma_cache_inv)(unsigned long start, unsigned long size);
+
+#endif /* CONFIG_DMA_NONCOHERENT */
+
+/*
+ * We could optimize the case where the cache argument is not BCACHE but
+ * that seems very atypical use ...
+ */
+SYSCALL_DEFINE3(cacheflush, unsigned long, addr, unsigned long, bytes,
+	unsigned int, cache)
+{
+	if (bytes == 0)
+		return 0;
+	if (!access_ok((void __user *) addr, bytes))
+		return -EFAULT;
+
+	__flush_icache_user_range(addr, addr + bytes);
+
+	return 0;
+}
+
+void __flush_dcache_folio_pages(struct folio *folio, struct page *page,
+		unsigned int nr)
+{
+	struct address_space *mapping = folio_flush_mapping(folio);
+	unsigned long addr;
+	unsigned int i;
+
+	if (mapping && !mapping_mapped(mapping)) {
+		folio_set_dcache_dirty(folio);
+		return;
+	}
+
+	/*
+	 * We could delay the flush for the !folio_mapping case too.  But that
+	 * case is for exec env/arg pages and those are %99 certainly going to
+	 * get faulted into the tlb (and thus flushed) anyways.
+	 */
+	for (i = 0; i < nr; i++) {
+		addr = (unsigned long)kmap_local_page(page + i);
+		flush_data_cache_page(addr);
+		kunmap_local((void *)addr);
+	}
+}
+EXPORT_SYMBOL(__flush_dcache_folio_pages);
+
+void __flush_anon_page(struct page *page, unsigned long vmaddr)
+{
+	unsigned long addr = (unsigned long) page_address(page);
+	struct folio *folio = page_folio(page);
+
+	if (pages_do_alias(addr, vmaddr)) {
+		if (folio_mapped(folio) && !folio_test_dcache_dirty(folio)) {
+			void *kaddr;
+
+			kaddr = kmap_coherent(page, vmaddr);
+			flush_data_cache_page((unsigned long)kaddr);
+			kunmap_coherent();
+		} else
+			flush_data_cache_page(addr);
+	}
+}
+
+EXPORT_SYMBOL(__flush_anon_page);
+
+void __update_cache(unsigned long address, pte_t pte)
+{
+	struct folio *folio;
+	unsigned long pfn, addr;
+	int exec = !pte_no_exec(pte) && !cpu_has_ic_fills_f_dc;
+	unsigned int i;
+
+	pfn = pte_pfn(pte);
+	if (unlikely(!pfn_valid(pfn)))
+		return;
+
+	folio = page_folio(pfn_to_page(pfn));
+	address &= PAGE_MASK;
+	address -= offset_in_folio(folio, pfn << PAGE_SHIFT);
+
+	if (folio_test_dcache_dirty(folio)) {
+		for (i = 0; i < folio_nr_pages(folio); i++) {
+			addr = (unsigned long)kmap_local_folio(folio, i);
+
+			if (exec || pages_do_alias(addr, address))
+				flush_data_cache_page(addr);
+			kunmap_local((void *)addr);
+			address += PAGE_SIZE;
+		}
+		folio_clear_dcache_dirty(folio);
+	}
+}
+
+unsigned long _page_cachable_default;
+EXPORT_SYMBOL(_page_cachable_default);
+
+#define PM(p)	__pgprot(_page_cachable_default | (p))
+
+static pgprot_t protection_map[16] __ro_after_init;
+DECLARE_VM_GET_PAGE_PROT
+
+static inline void setup_protection_map(void)
+{
+	protection_map[0]  = PM(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
+	protection_map[1]  = PM(_PAGE_PRESENT | _PAGE_NO_EXEC);
+	protection_map[2]  = PM(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
+	protection_map[3]  = PM(_PAGE_PRESENT | _PAGE_NO_EXEC);
+	protection_map[4]  = PM(_PAGE_PRESENT);
+	protection_map[5]  = PM(_PAGE_PRESENT);
+	protection_map[6]  = PM(_PAGE_PRESENT);
+	protection_map[7]  = PM(_PAGE_PRESENT);
+
+	protection_map[8]  = PM(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
+	protection_map[9]  = PM(_PAGE_PRESENT | _PAGE_NO_EXEC);
+	protection_map[10] = PM(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE |
+				_PAGE_NO_READ);
+	protection_map[11] = PM(_PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE);
+	protection_map[12] = PM(_PAGE_PRESENT);
+	protection_map[13] = PM(_PAGE_PRESENT);
+	protection_map[14] = PM(_PAGE_PRESENT | _PAGE_WRITE);
+	protection_map[15] = PM(_PAGE_PRESENT | _PAGE_WRITE);
+}
+
+#undef PM
+
+void cpu_cache_init(void)
+{
+	if (IS_ENABLED(CONFIG_CPU_R3000) && cpu_has_3k_cache)
+		r3k_cache_init();
+	if ((IS_ENABLED(CONFIG_CPU_R4K_CACHE_TLB) ||
+	     IS_ENABLED(CONFIG_CPU_SB1)) && cpu_has_4k_cache)
+		r4k_cache_init();
+
+	if (IS_ENABLED(CONFIG_CPU_CAVIUM_OCTEON) && cpu_has_octeon_cache)
+		octeon_cache_init();
+
+	setup_protection_map();
+}