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/char/adi.c | 232 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 232 insertions(+) create mode 100644 drivers/char/adi.c (limited to 'drivers/char/adi.c') diff --git a/drivers/char/adi.c b/drivers/char/adi.c new file mode 100644 index 000000000..0849d933a --- /dev/null +++ b/drivers/char/adi.c @@ -0,0 +1,232 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Privileged ADI driver for sparc64 + * + * Author: Tom Hromatka + */ +#include +#include +#include +#include +#include +#include +#include + +#define MAX_BUF_SZ PAGE_SIZE + +static int read_mcd_tag(unsigned long addr) +{ + long err; + int ver; + + __asm__ __volatile__( + "1: ldxa [%[addr]] %[asi], %[ver]\n" + " mov 0, %[err]\n" + "2:\n" + " .section .fixup,#alloc,#execinstr\n" + " .align 4\n" + "3: sethi %%hi(2b), %%g1\n" + " jmpl %%g1 + %%lo(2b), %%g0\n" + " mov %[invalid], %[err]\n" + " .previous\n" + " .section __ex_table, \"a\"\n" + " .align 4\n" + " .word 1b, 3b\n" + " .previous\n" + : [ver] "=r" (ver), [err] "=r" (err) + : [addr] "r" (addr), [invalid] "i" (EFAULT), + [asi] "i" (ASI_MCD_REAL) + : "memory", "g1" + ); + + if (err) + return -EFAULT; + else + return ver; +} + +static ssize_t adi_read(struct file *file, char __user *buf, + size_t count, loff_t *offp) +{ + size_t ver_buf_sz, bytes_read = 0; + int ver_buf_idx = 0; + loff_t offset; + u8 *ver_buf; + ssize_t ret; + + ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ); + ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL); + if (!ver_buf) + return -ENOMEM; + + offset = (*offp) * adi_blksize(); + + while (bytes_read < count) { + ret = read_mcd_tag(offset); + if (ret < 0) + goto out; + + ver_buf[ver_buf_idx] = (u8)ret; + ver_buf_idx++; + offset += adi_blksize(); + + if (ver_buf_idx >= ver_buf_sz) { + if (copy_to_user(buf + bytes_read, ver_buf, + ver_buf_sz)) { + ret = -EFAULT; + goto out; + } + + bytes_read += ver_buf_sz; + ver_buf_idx = 0; + + ver_buf_sz = min_t(size_t, count - bytes_read, + MAX_BUF_SZ); + } + } + + (*offp) += bytes_read; + ret = bytes_read; +out: + kfree(ver_buf); + return ret; +} + +static int set_mcd_tag(unsigned long addr, u8 ver) +{ + long err; + + __asm__ __volatile__( + "1: stxa %[ver], [%[addr]] %[asi]\n" + " mov 0, %[err]\n" + "2:\n" + " .section .fixup,#alloc,#execinstr\n" + " .align 4\n" + "3: sethi %%hi(2b), %%g1\n" + " jmpl %%g1 + %%lo(2b), %%g0\n" + " mov %[invalid], %[err]\n" + " .previous\n" + " .section __ex_table, \"a\"\n" + " .align 4\n" + " .word 1b, 3b\n" + " .previous\n" + : [err] "=r" (err) + : [ver] "r" (ver), [addr] "r" (addr), + [invalid] "i" (EFAULT), [asi] "i" (ASI_MCD_REAL) + : "memory", "g1" + ); + + if (err) + return -EFAULT; + else + return ver; +} + +static ssize_t adi_write(struct file *file, const char __user *buf, + size_t count, loff_t *offp) +{ + size_t ver_buf_sz, bytes_written = 0; + loff_t offset; + u8 *ver_buf; + ssize_t ret; + int i; + + if (count == 0) + return -EINVAL; + + ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ); + ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL); + if (!ver_buf) + return -ENOMEM; + + offset = (*offp) * adi_blksize(); + + do { + if (copy_from_user(ver_buf, &buf[bytes_written], + ver_buf_sz)) { + ret = -EFAULT; + goto out; + } + + for (i = 0; i < ver_buf_sz; i++) { + ret = set_mcd_tag(offset, ver_buf[i]); + if (ret < 0) + goto out; + + offset += adi_blksize(); + } + + bytes_written += ver_buf_sz; + ver_buf_sz = min_t(size_t, count - bytes_written, MAX_BUF_SZ); + } while (bytes_written < count); + + (*offp) += bytes_written; + ret = bytes_written; +out: + __asm__ __volatile__("membar #Sync"); + kfree(ver_buf); + return ret; +} + +static loff_t adi_llseek(struct file *file, loff_t offset, int whence) +{ + loff_t ret = -EINVAL; + + switch (whence) { + case SEEK_END: + case SEEK_DATA: + case SEEK_HOLE: + /* unsupported */ + return -EINVAL; + case SEEK_CUR: + if (offset == 0) + return file->f_pos; + + offset += file->f_pos; + break; + case SEEK_SET: + break; + } + + if (offset != file->f_pos) { + file->f_pos = offset; + ret = offset; + } + + return ret; +} + +static const struct file_operations adi_fops = { + .owner = THIS_MODULE, + .llseek = adi_llseek, + .read = adi_read, + .write = adi_write, + .fop_flags = FOP_UNSIGNED_OFFSET, +}; + +static struct miscdevice adi_miscdev = { + .minor = MISC_DYNAMIC_MINOR, + .name = KBUILD_MODNAME, + .fops = &adi_fops, +}; + +static int __init adi_init(void) +{ + if (!adi_capable()) + return -EPERM; + + return misc_register(&adi_miscdev); +} + +static void __exit adi_exit(void) +{ + misc_deregister(&adi_miscdev); +} + +module_init(adi_init); +module_exit(adi_exit); + +MODULE_AUTHOR("Tom Hromatka "); +MODULE_DESCRIPTION("Privileged interface to ADI"); +MODULE_VERSION("1.0"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1