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))
How this pattern is working depends 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.
Rework raw_x_guest() code to use required functions explicitly for each
combination of CONFIG_PV/CONFIG_HVM with main intention to optimize code for
(PV=n and HVM=y) case.
For the case (PV=n and HVM=n) empty stubs are created which return (1)
indicating failure. Hence, no guests should possible in this case -
which means no access to guest memory should ever happen.
The two calls of __raw_copy_to_guest() in
common/domain.c->update_runstate_area()
are fixed for this case by explicitly cast the return value to void
(MISRA C Rule 17.7).
Finally build arch/x86/usercopy.c only for PV=y.
The measured (bloat-o-meter) improvement for (PV=n and HVM=y) case is:
add/remove: 0/10 grow/shrink: 2/90 up/down: 163/-30932 (-30769)
Total: Before=1937113, After=1906344, chg -1.59%
Signed-off-by: Grygorii Strashko <[email protected]>
---
xen/arch/x86/Makefile | 2 +-
xen/arch/x86/include/asm/guest_access.h | 38 +++++++++++++++++++++++++
xen/common/domain.c | 10 ++++---
3 files changed, 45 insertions(+), 5 deletions(-)
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 407571c510e1..27f131ffeb61 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -71,7 +71,7 @@ obj-y += time.o
obj-y += traps-setup.o
obj-y += traps.o
obj-$(CONFIG_INTEL) += tsx.o
-obj-y += usercopy.o
+obj-$(CONFIG_PV) += usercopy.o
obj-y += x86_emulate.o
obj-$(CONFIG_TBOOT) += tboot.o
obj-y += hpet.o
diff --git a/xen/arch/x86/include/asm/guest_access.h
b/xen/arch/x86/include/asm/guest_access.h
index 69716c8b41bb..36aeb89524ab 100644
--- a/xen/arch/x86/include/asm/guest_access.h
+++ b/xen/arch/x86/include/asm/guest_access.h
@@ -13,6 +13,7 @@
#include <asm/hvm/guest_access.h>
/* Raw access functions: no type checking. */
+#if defined(CONFIG_PV) && defined(CONFIG_HVM)
#define raw_copy_to_guest(dst, src, len) \
(is_hvm_vcpu(current) ? \
copy_to_user_hvm((dst), (src), (len)) : \
@@ -34,6 +35,43 @@
copy_from_user_hvm((dst), (src), (len)) : \
__copy_from_guest_pv(dst, src, len))
+#elif defined(CONFIG_HVM)
+#define raw_copy_to_guest(dst, src, len) \
+ copy_to_user_hvm((dst), (src), (len))
+#define raw_copy_from_guest(dst, src, len) \
+ copy_from_user_hvm((dst), (src), (len))
+#define raw_clear_guest(dst, len) \
+ clear_user_hvm((dst), (len))
+#define __raw_copy_to_guest(dst, src, len) \
+ copy_to_user_hvm((dst), (src), (len))
+#define __raw_copy_from_guest(dst, src, len) \
+ copy_from_user_hvm((dst), (src), (len))
+
+#elif defined(CONFIG_PV)
+#define raw_copy_to_guest(dst, src, len) \
+ copy_to_guest_pv(dst, src, len)
+#define raw_copy_from_guest(dst, src, len) \
+ copy_from_guest_pv(dst, src, len)
+#define raw_clear_guest(dst, len) \
+ clear_guest_pv(dst, len)
+#define __raw_copy_to_guest(dst, src, len) \
+ __copy_to_guest_pv(dst, src, len)
+#define __raw_copy_from_guest(dst, src, len) \
+ __copy_from_guest_pv(dst, src, len)
+
+#else
+#define raw_copy_to_guest(dst, src, len) \
+ ((void)(dst), (void)(src), (void)(len), 1)
+#define raw_copy_from_guest(dst, src, len) \
+ ((void)(dst), (void)(src), (void)(len), 1)
+#define raw_clear_guest(dst, len) \
+ ((void)(dst), (void)(len), 1)
+#define __raw_copy_to_guest(dst, src, len) \
+ ((void)(dst), (void)(src), (void)(len), 1)
+#define __raw_copy_from_guest(dst, src, len) \
+ ((void)(dst), (void)(src), (void)(len), 1)
+#endif
+
/*
* Pre-validate a guest handle.
* Allows use of faster __copy_* functions.
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 4f91316ad93e..c603edcc7d46 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1985,8 +1985,9 @@ bool update_runstate_area(struct vcpu *v)
#endif
guest_handle--;
runstate.state_entry_time |= XEN_RUNSTATE_UPDATE;
- __raw_copy_to_guest(guest_handle,
- (void *)(&runstate.state_entry_time + 1) - 1, 1);
+ (void)__raw_copy_to_guest(guest_handle,
+ (void *)(&runstate.state_entry_time + 1) - 1,
+ 1);
smp_wmb();
}
@@ -2008,8 +2009,9 @@ bool update_runstate_area(struct vcpu *v)
{
runstate.state_entry_time &= ~XEN_RUNSTATE_UPDATE;
smp_wmb();
- __raw_copy_to_guest(guest_handle,
- (void *)(&runstate.state_entry_time + 1) - 1, 1);
+ (void)__raw_copy_to_guest(guest_handle,
+ (void *)(&runstate.state_entry_time + 1) - 1,
+ 1);
}
update_guest_memory_policy(v, &policy);
--
2.34.1
