diff options
| author | Joerg Roedel | 2021-03-03 15:17:14 +0100 |
|---|---|---|
| committer | Borislav Petkov | 2021-03-19 13:37:22 +0100 |
| commit | 799de1baaf3509a54ff713efb768020f8defd709 (patch) | |
| tree | dad083a50444ac298a5ff450f02e9c29753637ad /arch/x86 | |
| parent | f15a0a732aefb46f999c2a8aa8f9f16e71cec5b2 (diff) | |
x86/sev-es: Optimize __sev_es_ist_enter() for better readability
Reorganize the code and improve the comments to make the function more
readable and easier to understand.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210303141716.29223-4-joro@8bytes.org
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/sev-es.c | 36 |
1 files changed, 24 insertions, 12 deletions
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c index 225704ed2055..26f5479a97a8 100644 --- a/arch/x86/kernel/sev-es.c +++ b/arch/x86/kernel/sev-es.c @@ -137,29 +137,41 @@ static __always_inline bool on_vc_stack(struct pt_regs *regs) } /* - * This function handles the case when an NMI is raised in the #VC exception - * handler entry code. In this case, the IST entry for #VC must be adjusted, so - * that any subsequent #VC exception will not overwrite the stack contents of the - * interrupted #VC handler. + * This function handles the case when an NMI is raised in the #VC + * exception handler entry code, before the #VC handler has switched off + * its IST stack. In this case, the IST entry for #VC must be adjusted, + * so that any nested #VC exception will not overwrite the stack + * contents of the interrupted #VC handler. * * The IST entry is adjusted unconditionally so that it can be also be - * unconditionally adjusted back in sev_es_ist_exit(). Otherwise a nested - * sev_es_ist_exit() call may adjust back the IST entry too early. + * unconditionally adjusted back in __sev_es_ist_exit(). Otherwise a + * nested sev_es_ist_exit() call may adjust back the IST entry too + * early. + * + * The __sev_es_ist_enter() and __sev_es_ist_exit() functions always run + * on the NMI IST stack, as they are only called from NMI handling code + * right now. */ void noinstr __sev_es_ist_enter(struct pt_regs *regs) { unsigned long old_ist, new_ist; /* Read old IST entry */ - old_ist = __this_cpu_read(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC]); + new_ist = old_ist = __this_cpu_read(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC]); - /* Make room on the IST stack */ + /* + * If NMI happened while on the #VC IST stack, set the new IST + * value below regs->sp, so that the interrupted stack frame is + * not overwritten by subsequent #VC exceptions. + */ if (on_vc_stack(regs)) - new_ist = ALIGN_DOWN(regs->sp, 8) - sizeof(old_ist); - else - new_ist = old_ist - sizeof(old_ist); + new_ist = regs->sp; - /* Store old IST entry */ + /* + * Reserve additional 8 bytes and store old IST value so this + * adjustment can be unrolled in __sev_es_ist_exit(). + */ + new_ist -= sizeof(old_ist); *(unsigned long *)new_ist = old_ist; /* Set new IST entry */ |