Mailing List Archive

# HG changeset patch
# User Keir Fraser <keir.fraser@citrix.com>
# Date 1273563298 -3600
# Node ID 804304d4e05d98289de9a107c6b26c5a1db09cd8
# Parent a915a11908e3ab970887a313279650bc1d50c539
x86: TSC handling cleanups

"I am removing the tsc_scaled variable that is never actually used
because when tsc needs to be scaled vtsc is 1. I am also making this
more explicit in tsc_set_info. I am also removing hvm_domain.gtsc_khz
that is a duplicate of d->arch.tsc_khz. I am using scale_delta(delta,
&d->arch.ns_to_vtsc) to scale the tsc value before returning it to the
guest like in the pv case. I added a feature flag to specify that the
pvclock algorithm is safe to be used in an HVM guest so that the guest
can now use it without hanging."

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
xen/arch/x86/hvm/hvm.c | 30 ++----------------------------
xen/arch/x86/hvm/save.c | 6 +++---
xen/arch/x86/hvm/vpt.c | 3 ---
xen/arch/x86/time.c | 31 +++++++++++++++++++++++--------
xen/common/kernel.c | 2 ++
xen/include/asm-x86/hvm/domain.h | 2 --
xen/include/asm-x86/hvm/hvm.h | 1 -
xen/include/asm-x86/time.h | 1 +
xen/include/public/features.h | 3 +++
9 files changed, 34 insertions(+), 45 deletions(-)

diff -r a915a11908e3 -r 804304d4e05d xen/arch/x86/hvm/hvm.c
--- a/xen/arch/x86/hvm/hvm.c Tue May 11 08:31:16 2010 +0100
+++ b/xen/arch/x86/hvm/hvm.c Tue May 11 08:34:58 2010 +0100
@@ -153,32 +153,6 @@ void hvm_set_rdtsc_exiting(struct domain
hvm_funcs.set_rdtsc_exiting(v, enable);
}

-int hvm_gtsc_need_scale(struct domain *d)
-{
- uint32_t gtsc_mhz, htsc_mhz;
-
- if ( d->arch.vtsc )
- return 0;
-
- gtsc_mhz = d->arch.hvm_domain.gtsc_khz / 1000;
- htsc_mhz = (uint32_t)cpu_khz / 1000;
-
- d->arch.hvm_domain.tsc_scaled = (gtsc_mhz && (gtsc_mhz != htsc_mhz));
- return d->arch.hvm_domain.tsc_scaled;
-}
-
-static u64 hvm_h2g_scale_tsc(struct vcpu *v, u64 host_tsc)
-{
- uint32_t gtsc_khz, htsc_khz;
-
- if ( !v->domain->arch.hvm_domain.tsc_scaled )
- return host_tsc;
-
- htsc_khz = cpu_khz;
- gtsc_khz = v->domain->arch.hvm_domain.gtsc_khz;
- return muldiv64(host_tsc, gtsc_khz, htsc_khz);
-}
-
void hvm_set_guest_tsc(struct vcpu *v, u64 guest_tsc)
{
uint64_t tsc;
@@ -186,11 +160,11 @@ void hvm_set_guest_tsc(struct vcpu *v, u
if ( v->domain->arch.vtsc )
{
tsc = hvm_get_guest_time(v);
+ tsc = gtime_to_gtsc(v->domain, tsc);
}
else
{
rdtscll(tsc);
- tsc = hvm_h2g_scale_tsc(v, tsc);
}

v->arch.hvm_vcpu.cache_tsc_offset = guest_tsc - tsc;
@@ -204,12 +178,12 @@ u64 hvm_get_guest_tsc(struct vcpu *v)
if ( v->domain->arch.vtsc )
{
tsc = hvm_get_guest_time(v);
+ tsc = gtime_to_gtsc(v->domain, tsc);
v->domain->arch.vtsc_kerncount++;
}
else
{
rdtscll(tsc);
- tsc = hvm_h2g_scale_tsc(v, tsc);
}

return tsc + v->arch.hvm_vcpu.cache_tsc_offset;
diff -r a915a11908e3 -r 804304d4e05d xen/arch/x86/hvm/save.c
--- a/xen/arch/x86/hvm/save.c Tue May 11 08:31:16 2010 +0100
+++ b/xen/arch/x86/hvm/save.c Tue May 11 08:34:58 2010 +0100
@@ -33,7 +33,7 @@ void arch_hvm_save(struct domain *d, str
hdr->cpuid = eax;

/* Save guest's preferred TSC. */
- hdr->gtsc_khz = d->arch.hvm_domain.gtsc_khz;
+ hdr->gtsc_khz = d->arch.tsc_khz;
}

int arch_hvm_load(struct domain *d, struct hvm_save_header *hdr)
@@ -62,8 +62,8 @@ int arch_hvm_load(struct domain *d, stru

/* Restore guest's preferred TSC frequency. */
if ( hdr->gtsc_khz )
- d->arch.hvm_domain.gtsc_khz = hdr->gtsc_khz;
- if ( hvm_gtsc_need_scale(d) )
+ d->arch.tsc_khz = hdr->gtsc_khz;
+ if ( d->arch.vtsc )
{
hvm_set_rdtsc_exiting(d, 1);
gdprintk(XENLOG_WARNING, "Domain %d expects freq %uMHz "
diff -r a915a11908e3 -r 804304d4e05d xen/arch/x86/hvm/vpt.c
--- a/xen/arch/x86/hvm/vpt.c Tue May 11 08:31:16 2010 +0100
+++ b/xen/arch/x86/hvm/vpt.c Tue May 11 08:34:58 2010 +0100
@@ -32,9 +32,6 @@ void hvm_init_guest_time(struct domain *
spin_lock_init(&pl->pl_time_lock);
pl->stime_offset = -(u64)get_s_time();
pl->last_guest_time = 0;
-
- d->arch.hvm_domain.gtsc_khz = cpu_khz;
- d->arch.hvm_domain.tsc_scaled = 0;
}

u64 hvm_get_guest_time(struct vcpu *v)
diff -r a915a11908e3 -r 804304d4e05d xen/arch/x86/time.c
--- a/xen/arch/x86/time.c Tue May 11 08:31:16 2010 +0100
+++ b/xen/arch/x86/time.c Tue May 11 08:34:58 2010 +0100
@@ -828,8 +828,13 @@ static void __update_vcpu_system_time(st

if ( d->arch.vtsc )
{
- u64 delta = max_t(s64, t->stime_local_stamp - d->arch.vtsc_offset, 0);
- tsc_stamp = scale_delta(delta, &d->arch.ns_to_vtsc);
+ u64 stime = t->stime_local_stamp;
+ if ( is_hvm_domain(d) )
+ {
+ struct pl_time *pl = &v->domain->arch.hvm_domain.pl_time;
+ stime += pl->stime_offset + v->arch.hvm_vcpu.stime_offset;
+ }
+ tsc_stamp = gtime_to_gtsc(d, stime);
}
else
{
@@ -852,6 +857,8 @@ static void __update_vcpu_system_time(st
_u.tsc_to_system_mul = t->tsc_scale.mul_frac;
_u.tsc_shift = (s8)t->tsc_scale.shift;
}
+ if ( is_hvm_domain(d) )
+ _u.tsc_timestamp += v->arch.hvm_vcpu.cache_tsc_offset;

/* Don't bother unless timestamp record has changed or we are forced. */
_u.version = u->version; /* make versions match for memcmp test */
@@ -1618,11 +1625,18 @@ struct tm wallclock_time(void)
* PV SoftTSC Emulation.
*/

+u64 gtime_to_gtsc(struct domain *d, u64 tsc)
+{
+ if ( !is_hvm_domain(d) )
+ tsc = max_t(s64, tsc - d->arch.vtsc_offset, 0);
+ return scale_delta(tsc, &d->arch.ns_to_vtsc);
+}
+
void pv_soft_rdtsc(struct vcpu *v, struct cpu_user_regs *regs, int rdtscp)
{
s_time_t now = get_s_time();
struct domain *d = v->domain;
- u64 delta;
+ u64 tsc;

spin_lock(&d->arch.vtsc_lock);

@@ -1638,8 +1652,7 @@ void pv_soft_rdtsc(struct vcpu *v, struc

spin_unlock(&d->arch.vtsc_lock);

- delta = max_t(s64, now - d->arch.vtsc_offset, 0);
- now = scale_delta(delta, &d->arch.ns_to_vtsc);
+ tsc = gtime_to_gtsc(d, now);

regs->eax = (uint32_t)now;
regs->edx = (uint32_t)(now >> 32);
@@ -1780,8 +1793,10 @@ void tsc_set_info(struct domain *d,
d->arch.vtsc_offset = get_s_time() - elapsed_nsec;
d->arch.tsc_khz = gtsc_khz ? gtsc_khz : cpu_khz;
set_time_scale(&d->arch.vtsc_to_ns, d->arch.tsc_khz * 1000 );
- /* use native TSC if initial host has safe TSC and not migrated yet */
- if ( host_tsc_is_safe() && incarnation == 0 )
+ /* use native TSC if initial host has safe TSC, has not migrated
+ * yet and tsc_khz == cpu_khz */
+ if ( host_tsc_is_safe() && incarnation == 0 &&
+ d->arch.tsc_khz == cpu_khz )
d->arch.vtsc = 0;
else
d->arch.ns_to_vtsc = scale_reciprocal(d->arch.vtsc_to_ns);
@@ -1806,7 +1821,7 @@ void tsc_set_info(struct domain *d,
}
d->arch.incarnation = incarnation + 1;
if ( is_hvm_domain(d) )
- hvm_set_rdtsc_exiting(d, d->arch.vtsc || hvm_gtsc_need_scale(d));
+ hvm_set_rdtsc_exiting(d, d->arch.vtsc);
}

/* vtsc may incur measurable performance degradation, diagnose with this */
diff -r a915a11908e3 -r 804304d4e05d xen/common/kernel.c
--- a/xen/common/kernel.c Tue May 11 08:31:16 2010 +0100
+++ b/xen/common/kernel.c Tue May 11 08:34:58 2010 +0100
@@ -243,6 +243,8 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDL
fi.submap |= (1U << XENFEAT_mmu_pt_update_preserve_ad) |
(1U << XENFEAT_highmem_assist) |
(1U << XENFEAT_gnttab_map_avail_bits);
+ else
+ fi.submap |= (1U << XENFEAT_hvm_safe_pvclock);
#endif
break;
default:
diff -r a915a11908e3 -r 804304d4e05d xen/include/asm-x86/hvm/domain.h
--- a/xen/include/asm-x86/hvm/domain.h Tue May 11 08:31:16 2010 +0100
+++ b/xen/include/asm-x86/hvm/domain.h Tue May 11 08:34:58 2010 +0100
@@ -45,8 +45,6 @@ struct hvm_domain {
struct hvm_ioreq_page ioreq;
struct hvm_ioreq_page buf_ioreq;

- uint32_t gtsc_khz; /* kHz */
- bool_t tsc_scaled;
struct pl_time pl_time;

struct hvm_io_handler io_handler;
diff -r a915a11908e3 -r 804304d4e05d xen/include/asm-x86/hvm/hvm.h
--- a/xen/include/asm-x86/hvm/hvm.h Tue May 11 08:31:16 2010 +0100
+++ b/xen/include/asm-x86/hvm/hvm.h Tue May 11 08:34:58 2010 +0100
@@ -294,7 +294,6 @@ uint8_t hvm_combine_hw_exceptions(uint8_
uint8_t hvm_combine_hw_exceptions(uint8_t vec1, uint8_t vec2);

void hvm_set_rdtsc_exiting(struct domain *d, bool_t enable);
-int hvm_gtsc_need_scale(struct domain *d);

static inline int
hvm_cpu_prepare(unsigned int cpu)
diff -r a915a11908e3 -r 804304d4e05d xen/include/asm-x86/time.h
--- a/xen/include/asm-x86/time.h Tue May 11 08:31:16 2010 +0100
+++ b/xen/include/asm-x86/time.h Tue May 11 08:34:58 2010 +0100
@@ -60,6 +60,7 @@ uint64_t ns_to_acpi_pm_tick(uint64_t ns)
uint64_t ns_to_acpi_pm_tick(uint64_t ns);

void pv_soft_rdtsc(struct vcpu *v, struct cpu_user_regs *regs, int rdtscp);
+u64 gtime_to_gtsc(struct domain *d, u64 tsc);

void tsc_set_info(struct domain *d, uint32_t tsc_mode, uint64_t elapsed_nsec,
uint32_t gtsc_khz, uint32_t incarnation);
diff -r a915a11908e3 -r 804304d4e05d xen/include/public/features.h
--- a/xen/include/public/features.h Tue May 11 08:31:16 2010 +0100
+++ b/xen/include/public/features.h Tue May 11 08:34:58 2010 +0100
@@ -68,6 +68,9 @@
*/
#define XENFEAT_gnttab_map_avail_bits 7

+/* x86: pvclock algorithm is safe to use on HVM */
+#define XENFEAT_hvm_safe_pvclock 9
+
#define XENFEAT_NR_SUBMAPS 1

#endif /* __XEN_PUBLIC_FEATURES_H__ */

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