The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: b250f2f7792d15bcde98e0456781e2835556d5fa Gitweb: https://git.kernel.org/tip/b250f2f7792d15bcde98e0456781e2835556d5fa Author: Joerg Roedel jroedel@suse.de AuthorDate: Wed, 19 May 2021 15:52:44 +02:00 Committer: Borislav Petkov bp@suse.de CommitterDate: Wed, 19 May 2021 17:05:13 +02:00

x86/sev-es: Don't return NULL from sev_es_get_ghcb()

sev_es_get_ghcb() is called from several places but only one of them checks the return value. The reaction to returning NULL is always the same: calling panic() and kill the machine.

Instead of adding checks to all call sites, move the panic() into the function itself so that it will no longer return NULL.

Fixes: 0786138c78e7 ("x86/sev-es: Add a Runtime #VC Exception Handler") Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Borislav Petkov bp@suse.de Cc: stable@vger.kernel.org # v5.10+ Link: https://lkml.kernel.org/r/20210519135251.30093-2-joro@8bytes.org --- arch/x86/kernel/sev.c | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index 4fa111b..82bced8 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -203,8 +203,18 @@ static __always_inline struct ghcb *sev_es_get_ghcb(struct ghcb_state *state) if (unlikely(data->ghcb_active)) { /* GHCB is already in use - save its contents */

- if (unlikely(data->backup_ghcb_active)) - return NULL; + if (unlikely(data->backup_ghcb_active)) { + /* + * Backup-GHCB is also already in use. There is no way + * to continue here so just kill the machine. To make + * panic() work, mark GHCBs inactive so that messages + * can be printed out. + */ + data->ghcb_active = false; + data->backup_ghcb_active = false; + + panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use"); + }

/* Mark backup_ghcb active before writing to it */ data->backup_ghcb_active = true; @@ -1289,7 +1299,6 @@ static __always_inline bool on_vc_fallback_stack(struct pt_regs *regs) */ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) { - struct sev_es_runtime_data *data = this_cpu_read(runtime_data); irqentry_state_t irq_state; struct ghcb_state state; struct es_em_ctxt ctxt; @@ -1315,16 +1324,6 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) */

ghcb = sev_es_get_ghcb(&state); - if (!ghcb) { - /* - * Mark GHCBs inactive so that panic() is able to print the - * message. - */ - data->ghcb_active = false; - data->backup_ghcb_active = false; - - panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use"); - }

vc_ghcb_invalidate(ghcb); result = vc_init_em_ctxt(&ctxt, regs, error_code);