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/video/console/dummycon.c | 159 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 159 insertions(+) create mode 100644 drivers/video/console/dummycon.c (limited to 'drivers/video/console/dummycon.c') diff --git a/drivers/video/console/dummycon.c b/drivers/video/console/dummycon.c new file mode 100644 index 000000000..7d02470f1 --- /dev/null +++ b/drivers/video/console/dummycon.c @@ -0,0 +1,159 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/drivers/video/dummycon.c -- A dummy console driver + * + * To be used if there's no other console driver (e.g. for plain VGA text) + * available, usually until fbcon takes console over. + */ + +#include +#include +#include +#include +#include +#include +#include + +/* + * Dummy console driver + */ + +#if defined(CONFIG_ARCH_FOOTBRIDGE) && defined(CONFIG_VGA_CONSOLE) +#include +#define DUMMY_COLUMNS vgacon_screen_info.orig_video_cols +#define DUMMY_ROWS vgacon_screen_info.orig_video_lines +#else +/* set by Kconfig. Use 80x25 for 640x480 and 160x64 for 1280x1024 */ +#define DUMMY_COLUMNS CONFIG_DUMMY_CONSOLE_COLUMNS +#define DUMMY_ROWS CONFIG_DUMMY_CONSOLE_ROWS +#endif + +#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER +/* These are both protected by the console_lock */ +static RAW_NOTIFIER_HEAD(dummycon_output_nh); +static bool dummycon_putc_called; + +void dummycon_register_output_notifier(struct notifier_block *nb) +{ + WARN_CONSOLE_UNLOCKED(); + + raw_notifier_chain_register(&dummycon_output_nh, nb); + + if (dummycon_putc_called) + nb->notifier_call(nb, 0, NULL); +} + +void dummycon_unregister_output_notifier(struct notifier_block *nb) +{ + WARN_CONSOLE_UNLOCKED(); + + raw_notifier_chain_unregister(&dummycon_output_nh, nb); +} + +static void dummycon_putc(struct vc_data *vc, u16 c, unsigned int y, + unsigned int x) +{ + WARN_CONSOLE_UNLOCKED(); + + dummycon_putc_called = true; + raw_notifier_call_chain(&dummycon_output_nh, 0, NULL); +} + +static void dummycon_putcs(struct vc_data *vc, const u16 *s, unsigned int count, + unsigned int ypos, unsigned int xpos) +{ + unsigned int i; + + if (!dummycon_putc_called) { + /* Ignore erases */ + for (i = 0 ; i < count; i++) { + if (s[i] != vc->vc_video_erase_char) + break; + } + if (i == count) + return; + + dummycon_putc_called = true; + } + + raw_notifier_call_chain(&dummycon_output_nh, 0, NULL); +} + +static bool dummycon_blank(struct vc_data *vc, enum vesa_blank_mode blank, + bool mode_switch) +{ + /* Redraw, so that we get putc(s) for output done while blanked */ + return true; +} + +static bool dummycon_switch(struct vc_data *vc) +{ + /* + * Redraw, so that we get putc(s) for output done while switched + * away. Informs deferred consoles to take over the display. + */ + return true; +} +#else +static void dummycon_putc(struct vc_data *vc, u16 c, unsigned int y, + unsigned int x) { } +static void dummycon_putcs(struct vc_data *vc, const u16 *s, unsigned int count, + unsigned int ypos, unsigned int xpos) { } +static bool dummycon_blank(struct vc_data *vc, enum vesa_blank_mode blank, + bool mode_switch) +{ + return false; +} +static bool dummycon_switch(struct vc_data *vc) +{ + return false; +} +#endif + +static const char *dummycon_startup(void) +{ + return "dummy device"; +} + +static void dummycon_init(struct vc_data *vc, bool init) +{ + vc->vc_can_do_color = 1; + if (init) { + vc->vc_cols = DUMMY_COLUMNS; + vc->vc_rows = DUMMY_ROWS; + } else + vc_resize(vc, DUMMY_COLUMNS, DUMMY_ROWS); +} + +static void dummycon_deinit(struct vc_data *vc) { } +static void dummycon_clear(struct vc_data *vc, unsigned int sy, unsigned int sx, + unsigned int width) { } +static void dummycon_cursor(struct vc_data *vc, bool enable) { } + +static bool dummycon_scroll(struct vc_data *vc, unsigned int top, + unsigned int bottom, enum con_scroll dir, + unsigned int lines) +{ + return false; +} + +/* + * The console `switch' structure for the dummy console + * + * Most of the operations are dummies. + */ + +const struct consw dummy_con = { + .owner = THIS_MODULE, + .con_startup = dummycon_startup, + .con_init = dummycon_init, + .con_deinit = dummycon_deinit, + .con_clear = dummycon_clear, + .con_putc = dummycon_putc, + .con_putcs = dummycon_putcs, + .con_cursor = dummycon_cursor, + .con_scroll = dummycon_scroll, + .con_switch = dummycon_switch, + .con_blank = dummycon_blank, +}; +EXPORT_SYMBOL_GPL(dummy_con); -- cgit v1.3.1