Le 18/12/2025 à 15:01, Grygorii Strashko a écrit : > From: Grygorii Strashko <[email protected]> > > Xen uses below pattern for raw_x_guest() functions: > > define raw_copy_to_guest(dst, src, len) \ > (is_hvm_vcpu(current) ? \ > copy_to_user_hvm((dst), (src), (len)) : \ > copy_to_guest_pv(dst, src, len)) > > This pattern works depending on CONFIG_PV/CONFIG_HVM as: > - PV=y and HVM=y > Proper guest access function is selected depending on domain type. > - PV=y and HVM=n > Only PV domains are possible. is_hvm_domain/vcpu() will constify to "false" > and compiler will optimize code and skip HVM specific part.
> - PV=n and HVM=y > Only HVM domains are possible. is_hvm_domain/vcpu() will not be constified. > No PV specific code will be optimized by compiler. > - PV=n and HVM=n > No guests should possible. The code will still follow PV path. > ^ regarding this > For the case (PV=n and HVM=n) return "len" value indicating a failure (no > guests should be possible in this case, which means no access to guest > memory should ever happen). > ^ and this AFAIU it is the same for PV=n and HVM=y for non-HVM domains (the few that "exists"), so we should rather say that these functions fails on "non-HVM" domains in PV=n configurations (since no actual PV domain exists in these cases). IOW, there is no PV path in PV=n configurations and in !HVM domains, the function fails instead (as we would expect). Once the commit message is adjusted on this Reviewed-by: Teddy Astie <[email protected]> > The measured (bloat-o-meter) improvement for (PV=n and HVM=y) case is about > -11K. > > [[email protected]: Suggested to use static inline functions vs > macro combinations] > Suggested-by: Teddy Astie <[email protected]> > Signed-off-by: Grygorii Strashko <[email protected]> > --- > changes in v5: > - rebase > - drop moving usercopy.c as it is not needed since commit 7370966d1cb7 > ("x86: move / split usercopy.c to / into arch-specific library") > > changes in v4: > - move usercopy.c into arch/x86/pv/ > - rework to always dynamically check for HVM vcpu(domain) by using > is_hvm_vcpu() > as requested by Jan Beulich > > changes in v3: > - add raw_use_hvm_access() wrapper > > changes in v2: > - use static inline functions instead of macro combinations > > xen/arch/x86/include/asm/guest_access.h | 78 ++++++++++++++++++------- > 1 file changed, 58 insertions(+), 20 deletions(-) > > diff --git a/xen/arch/x86/include/asm/guest_access.h > b/xen/arch/x86/include/asm/guest_access.h > index 69716c8b41bb..f0e56b112e14 100644 > --- a/xen/arch/x86/include/asm/guest_access.h > +++ b/xen/arch/x86/include/asm/guest_access.h > @@ -13,26 +13,64 @@ > #include <asm/hvm/guest_access.h> > > /* Raw access functions: no type checking. */ > -#define raw_copy_to_guest(dst, src, len) \ > - (is_hvm_vcpu(current) ? \ > - copy_to_user_hvm((dst), (src), (len)) : \ > - copy_to_guest_pv(dst, src, len)) > -#define raw_copy_from_guest(dst, src, len) \ > - (is_hvm_vcpu(current) ? \ > - copy_from_user_hvm((dst), (src), (len)) : \ > - copy_from_guest_pv(dst, src, len)) > -#define raw_clear_guest(dst, len) \ > - (is_hvm_vcpu(current) ? \ > - clear_user_hvm((dst), (len)) : \ > - clear_guest_pv(dst, len)) > -#define __raw_copy_to_guest(dst, src, len) \ > - (is_hvm_vcpu(current) ? \ > - copy_to_user_hvm((dst), (src), (len)) : \ > - __copy_to_guest_pv(dst, src, len)) > -#define __raw_copy_from_guest(dst, src, len) \ > - (is_hvm_vcpu(current) ? \ > - copy_from_user_hvm((dst), (src), (len)) : \ > - __copy_from_guest_pv(dst, src, len)) > +static inline unsigned int raw_copy_to_guest(void *dst, const void *src, > + unsigned int len) > +{ > + if ( is_hvm_vcpu(current) ) > + return copy_to_user_hvm(dst, src, len); > + > + if ( !IS_ENABLED(CONFIG_PV) ) > + return len; > + > + return copy_to_guest_pv(dst, src, len); > +} > + > +static inline unsigned int raw_copy_from_guest(void *dst, const void *src, > + unsigned int len) > +{ > + if ( is_hvm_vcpu(current) ) > + return copy_from_user_hvm(dst, src, len); > + > + if ( !IS_ENABLED(CONFIG_PV) ) > + return len; > + > + return copy_from_guest_pv(dst, src, len); > +} > + > +static inline unsigned int raw_clear_guest(void *dst, unsigned int len) > +{ > + if ( is_hvm_vcpu(current) ) > + return clear_user_hvm(dst, len); > + > + if ( !IS_ENABLED(CONFIG_PV) ) > + return len; > + > + return clear_guest_pv(dst, len); > +} > + > +static inline unsigned int __raw_copy_to_guest(void *dst, const void *src, > + unsigned int len) > +{ > + if ( is_hvm_vcpu(current) ) > + return copy_to_user_hvm(dst, src, len); > + > + if ( !IS_ENABLED(CONFIG_PV) ) > + return len; > + > + return __copy_to_guest_pv(dst, src, len); > +} > + > +static inline unsigned int __raw_copy_from_guest(void *dst, const void *src, > + unsigned int len) > +{ > + if ( is_hvm_vcpu(current) ) > + return copy_from_user_hvm(dst, src, len); > + > + if ( !IS_ENABLED(CONFIG_PV) ) > + return len; > + > + return __copy_from_guest_pv(dst, src, len); > +} > > /* > * Pre-validate a guest handle. Teddy -- Teddy Astie | Vates XCP-ng Developer XCP-ng & Xen Orchestra - Vates solutions web: https://vates.tech
