This patch adds a field tsc_scaling_ratio in struct hvm_vcpu to
record the TSC scaling ratio, and sets it up when tsc_set_info() is
called for a vcpu or when a vcpu is restored or reset.
Before applying the TSC scaling ratio to CPU, we check its validity in
tsc_set_info(). If an invalid ratio is given, we will leave the default
value in tsc_scaling_ratio (i.e. ratio = 1) and setup guest TSC as if no
TSC scaling is used:
* For TSC_MODE_FAULT,
- if a user-specified TSC frequency is given, we will set the guest
TSC frequency to it; otherwise, we set it to the host TSC frequency.
- if guest TSC frequency does not equal to host TSC frequency, we will
emulate guest TSC (i.e. d->arch.vtsc is set to 1). In both cases,
guest TSC runs in the guest TSC frequency.
* For TSC_MODE_PVRDTSCP,
- we set the guest TSC frequency to the host TSC frequency.
- guest rdtsc is executed natively in the host TSC frequency as
before.
- if rdtscp is not available to guest, it will be emulated; otherwise,
it will be executed natively. In both cases, guest rdtscp gets TSC
in the host TSC frequency as before.
Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
Changes in v3:
(addressing Boris Ostrovsky's comments)
* Remove redundant checks.
* Update comments in tsc_set_info(): during initial boot -> during domain
creation.
(addressing Kevin Tian's comments)
* Add a validation step to check TSC scaling ratio before applying it
to the hardware. If the validation fails, we will fallback to Xen's
original way to handle guest TSC. hvm_setup_tsc_scaling() is always
called when the validation succeeds, so it shoud never fail now.
xen/arch/x86/hvm/hvm.c | 41 +++++++++++++++++++++++++++++++++++++++
xen/arch/x86/hvm/svm/svm.c | 6 ++++--
xen/arch/x86/time.c | 19 +++++++++++++++---
xen/include/asm-x86/hvm/hvm.h | 6 ++++++
xen/include/asm-x86/hvm/svm/svm.h | 3 ---
xen/include/asm-x86/hvm/vcpu.h | 2 ++
6 files changed, 69 insertions(+), 8 deletions(-)
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 3648a44..3bf99b1 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -65,6 +65,7 @@
#include <asm/mtrr.h>
#include <asm/apic.h>
#include <asm/vm_event.h>
+#include <asm/math64.h>
#include <public/sched.h>
#include <public/hvm/ioreq.h>
#include <public/version.h>
@@ -301,6 +302,42 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
return 1;
}
+bool_t hvm_validate_tsc_scaling_ratio(uint32_t gtsc_khz)
+{
+ u64 ratio;
+
+ if ( !hvm_funcs.tsc_scaling_supported )
+ return FALSE;
+
+ ratio = mul_u64_u32_div(1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits,
+ gtsc_khz, cpu_khz);
+
+ return (!ratio || ratio > hvm_funcs.max_tsc_scaling_ratio) ? FALSE : TRUE;
+}
+
+void hvm_setup_tsc_scaling(struct vcpu *v)
+{
+ u64 ratio;
+
+ if ( !hvm_funcs.tsc_scaling_supported )
+ return;
+
+ /*
+ * The multiplication of the first two terms may overflow a 64-bit
+ * integer, so use mul_u64_u32_div() instead to keep precision.
+ */
+ ratio = mul_u64_u32_div(1ULL << hvm_funcs.tsc_scaling_ratio_frac_bits,
+ v->domain->arch.tsc_khz, cpu_khz);
+
+ if ( ratio == 0 || ratio > hvm_funcs.max_tsc_scaling_ratio )
+ return;
+
+ v->arch.hvm_vcpu.tsc_scaling_ratio = ratio;
+
+ if ( hvm_funcs.setup_tsc_scaling )
+ hvm_funcs.setup_tsc_scaling(v);
+}
