On 06/06/2024 12:04 pm, Sergiy Kibrik wrote: > Transactional Synchronization Extensions are available for certain Intel's > CPUs only, hence can be put under CONFIG_INTEL build option.
Careful with "available" vs "supported". They're only supported on certain Intel CPUs, but suffice it to say that c0dd53b8cb was discovered because of Xen's TSX unit testing. > > The whole TSX support, even if supported by CPU, may need to be disabled via > options, by microcode or through spec-ctrl, depending on a set of specific > conditions. To make sure nothing gets accidentally rutime-broken all runtime > modifications of global TSX configuration variables is secured by #ifdef's, > while variables themselves redefined to 0, so that ones can't mistakenly be > written to. > > Signed-off-by: Sergiy Kibrik <[email protected]> > --- > xen/arch/x86/Makefile | 2 +- > xen/arch/x86/include/asm/processor.h | 8 ++++++++ > xen/arch/x86/spec_ctrl.c | 4 ++++ > 3 files changed, 13 insertions(+), 1 deletion(-) This needs a command line adjustment too. diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc index 1dea7431fab6..c8d32c13bbaa 100644 --- a/docs/misc/xen-command-line.pandoc +++ b/docs/misc/xen-command-line.pandoc @@ -2584,10 +2584,11 @@ pages) must also be specified via the tbuf_size parameter. ### tsx = <bool> - Applicability: x86 + Applicability: x86 with CONFIG_INTEL active Default: false on parts vulnerable to TAA, true otherwise -Controls for the use of Transactional Synchronization eXtensions. +Controls for the use of Transactional Synchronization eXtensions, available if +Xen was compiled with `CONFIG_INTEL` active. Several microcode updates are relevant: > diff --git a/xen/arch/x86/include/asm/processor.h > b/xen/arch/x86/include/asm/processor.h > index c26ef9090c..8b12627ab0 100644 > --- a/xen/arch/x86/include/asm/processor.h > +++ b/xen/arch/x86/include/asm/processor.h > @@ -503,9 +503,17 @@ static inline uint8_t get_cpu_family(uint32_t raw, > uint8_t *model, > return fam; > } > > +#ifdef CONFIG_INTEL > extern int8_t opt_tsx; > extern bool rtm_disabled; > void tsx_init(void); > +#else > +#define opt_tsx 0 /* explicitly indicate TSX is off */ > +#define rtm_disabled false /* RTM was not force-disabled */ > +static inline void tsx_init(void) > +{ > +} For trivial things like this, we allow static inline void tsx_init(void) {} All can be fixed on commit, but none of this is tagged for 4.19 and is 4.20 material IMO. ~Andrew
