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 --- lib/argv_split.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) create mode 100644 lib/argv_split.c (limited to 'lib/argv_split.c') diff --git a/lib/argv_split.c b/lib/argv_split.c new file mode 100644 index 000000000..e28db8e3b --- /dev/null +++ b/lib/argv_split.c @@ -0,0 +1,95 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Helper function for splitting a string into an argv-like array. + */ + +#include +#include +#include +#include +#include + +static int count_argc(const char *str) +{ + int count = 0; + bool was_space; + + for (was_space = true; *str; str++) { + if (isspace(*str)) { + was_space = true; + } else if (was_space) { + was_space = false; + count++; + } + } + + return count; +} + +/** + * argv_free - free an argv + * @argv: the argument vector to be freed + * + * Frees an argv and the strings it points to. + */ +void argv_free(char **argv) +{ + argv--; + kfree(argv[0]); + kfree(argv); +} +EXPORT_SYMBOL(argv_free); + +/** + * argv_split - split a string at whitespace, returning an argv + * @gfp: the GFP mask used to allocate memory + * @str: the string to be split + * @argcp: returned argument count + * + * Returns: an array of pointers to strings which are split out from + * @str. This is performed by strictly splitting on white-space; no + * quote processing is performed. Multiple whitespace characters are + * considered to be a single argument separator. The returned array + * is always NULL-terminated. Returns NULL on memory allocation + * failure. + * + * The source string at `str' may be undergoing concurrent alteration via + * userspace sysctl activity (at least). The argv_split() implementation + * attempts to handle this gracefully by taking a local copy to work on. + */ +char **argv_split(gfp_t gfp, const char *str, int *argcp) +{ + char *argv_str; + bool was_space; + char **argv, **argv_ret; + int argc; + + argv_str = kstrndup(str, KMALLOC_MAX_SIZE - 1, gfp); + if (!argv_str) + return NULL; + + argc = count_argc(argv_str); + argv = kmalloc_array(argc + 2, sizeof(*argv), gfp); + if (!argv) { + kfree(argv_str); + return NULL; + } + + *argv = argv_str; + argv_ret = ++argv; + for (was_space = true; *argv_str; argv_str++) { + if (isspace(*argv_str)) { + was_space = true; + *argv_str = 0; + } else if (was_space) { + was_space = false; + *argv++ = argv_str; + } + } + *argv = NULL; + + if (argcp) + *argcp = argc; + return argv_ret; +} +EXPORT_SYMBOL(argv_split); -- cgit v1.3.1