On Wed, May 25, 2022 at 10:41:51AM +0200, Jan Beulich wrote: > 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.
Indeed. I had my addition properly parenthesized, but forgot to do it here when moving the line. Thanks, Roger.
