On 25.05.2022 10:13, Roger Pau Monne wrote: > Booting with Shadow Stacks leads to the following assert on a debug > hypervisor: > > Assertion 'local_irq_is_enabled()' failed at arch/x86/smp.c:265 > ----[ Xen-4.17.0-10.24-d x86_64 debug=y Not tainted ]---- > CPU: 0 > RIP: e008:[<ffff82d040345300>] flush_area_mask+0x40/0x13e > [...] > Xen call trace: > [<ffff82d040345300>] R flush_area_mask+0x40/0x13e > [<ffff82d040338a40>] F modify_xen_mappings+0xc5/0x958 > [<ffff82d0404474f9>] F > arch/x86/alternative.c#_alternative_instructions+0xb7/0xb9 > [<ffff82d0404476cc>] F alternative_branches+0xf/0x12 > [<ffff82d04044e37d>] F __start_xen+0x1ef4/0x2776 > [<ffff82d040203344>] F __high_start+0x94/0xa0 > > This is due to SYS_STATE_smp_boot being set before calling > alternative_branches(), and the flush in modify_xen_mappings() then > using flush_area_all() with interrupts disabled. Note that > alternative_branches() is called before APs are started, so the flush > must be a local one (and indeed the cpumask passed to > flush_area_mask() just contains one CPU). > > Take the opportunity to simplify a bit the logic and make flush_area() > an alias of flush_area_all() in mm.c, taking into account that > cpu_online_map just contains the BSP before APs are started. This > requires widening the assert in flush_area_mask() to allow being > called with interrupts disabled as long as it's strictly a local only > flush. > > The overall result is that a conditional can be removed from > flush_area(). > > While there also introduce an ASSERT to check that a vCPU state flush > is not issued for the local CPU only. > > Fixes: (78e072bc37 'x86/mm: avoid inadvertently degrading a TLB flush to > local only') > Suggested-by: Andrew Cooper <[email protected]> > Signed-off-by: Roger Pau Monné <[email protected]>
Reviewed-by: Jan Beulich <[email protected]> with ... > --- a/xen/arch/x86/mm.c > +++ b/xen/arch/x86/mm.c > @@ -5070,13 +5070,8 @@ l1_pgentry_t *virt_to_xen_l1e(unsigned long v) > #define l1f_to_lNf(f) (((f) & _PAGE_PRESENT) ? ((f) | _PAGE_PSE) : (f)) > #define lNf_to_l1f(f) (((f) & _PAGE_PRESENT) ? ((f) & ~_PAGE_PSE) : (f)) > > -/* > - * map_pages_to_xen() can be called early in boot before any other > - * CPUs are online. Use flush_area_local() in this case. > - */ > -#define flush_area(v,f) (system_state < SYS_STATE_smp_boot ? \ > - flush_area_local((const void *)v, f) : \ > - flush_area_all((const void *)v, f)) > +/* flush_area_all() can be used prior to any other CPU being online. */ > +#define flush_area(v, f) flush_area_all((const void *)v, f) ... v properly parenthesized here as the code is being touched anyway: One less Misra-C violation. This surely can be done while committing. Jan
