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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 1/4] x86/domctl: Implement XEN_DOMCTL_{get, set}_vcpu_msrs
Despite my 'Reviewed-by' tag on c/s 65e3554908 "x86/PV: support data
breakpoint extension registers", I have re-evaluated my position as far as the
hypercall interface is concerned.
Previously, for the sake of not modifying the migration code in libxc,
XEN_DOMCTL_get_ext_vcpucontext would jump though hoops to return -ENOBUFS if
and only if MSRs were in use and no buffer was present.
This is fragile, and awkward from a toolstack point-of-view when actually
sending MSR content in the migration stream. It also complicates fixing a
further race condition, between querying the number of MSRs for a vcpu, and
the vcpu touching a new one.
As this code is still only in staging, take this opportunity to redesign the
interface. This patch introduces the brand new XEN_DOMCTL_{get,set}_vcpu_msrs
subops.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
---
xen/arch/x86/domctl.c | 126 +++++++++++++++++++++++++++++++++++++++++++
xen/include/public/domctl.h | 31 +++++++++++
2 files changed, 157 insertions(+)
diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 1285dd0..c0c2d1b 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -1341,6 +1341,132 @@ long arch_do_domctl(
}
break;
+ case XEN_DOMCTL_get_vcpu_msrs:
+ case XEN_DOMCTL_set_vcpu_msrs:
+ {
+ struct xen_domctl_vcpu_msrs *vmsrs = &domctl->u.vcpu_msrs;
+ struct xen_domctl_vcpu_msr msr;
+ struct vcpu *v;
+ uint32_t nr_msrs = 0;
+
+ ret = -ESRCH;
+ if ( (vmsrs->vcpu >= d->max_vcpus) ||
+ ((v = d->vcpu[vmsrs->vcpu]) == NULL) )
+ break;
+
+ ret = -EINVAL;
+ if ( (v == current) || /* no vcpu_pause() */
+ !is_pv_domain(d) )
+ break;
+
+ /* Count maximum number of optional msrs. */
+ if ( boot_cpu_has(X86_FEATURE_DBEXT) )
+ nr_msrs += 4;
+
+ if ( domctl->cmd == XEN_DOMCTL_get_vcpu_msrs )
+ {
+ /* NULL guest handle is a request for max size. */
+ if ( guest_handle_is_null(vmsrs->msrs) ||
+ (vmsrs->msr_count < nr_msrs) )
+ {
+ vmsrs->msr_count = nr_msrs;
+ ret = guest_handle_is_null(vmsrs->msrs) ? 0 : -ENOBUFS;
+ }
+ else
+ {
+ ret = i = 0;
+
+ vcpu_pause(v);
+
+ if ( boot_cpu_has(X86_FEATURE_DBEXT) )
+ {
+ unsigned int j;
+
+ if ( v->arch.pv_vcpu.dr_mask[0] )
+ {
+ msr.index = MSR_AMD64_DR0_ADDRESS_MASK;
+ msr.reserved = 0;
+ msr.value = v->arch.pv_vcpu.dr_mask[0];
+ if ( copy_to_guest_offset(vmsrs->msrs, i, &msr, 1) )
+ ret = -EFAULT;
+ else
+ ++i;
+ }
+
+ for ( j = 0; j < 3; ++j )
+ {
+ if ( !v->arch.pv_vcpu.dr_mask[1 + j] )
+ continue;
+ if ( !ret )
+ {
+ msr.index = MSR_AMD64_DR1_ADDRESS_MASK + j;
+ msr.reserved = 0;
+ msr.value = v->arch.pv_vcpu.dr_mask[1 + j];
+ if ( copy_to_guest_offset(vmsrs->msrs, i, &msr, 1)
)
+ ret = -EFAULT;
+ else
+ ++i;
+ }
+ }
+
+ }
+
+ vcpu_unpause(v);
+
+ /* Check we didn't lie to userspace then overflow the buffer */
+ BUG_ON(i > nr_msrs);
+ vmsrs->msr_count = i;
+ }
+
+ copyback = 1;
+ }
+ else
+ {
+ ret = -EINVAL;
+ if ( vmsrs->msr_count > nr_msrs )
+ break;
+
+ vcpu_pause(v);
+
+ for ( i = 0; i < vmsrs->msr_count; ++i )
+ {
+ ret = -EFAULT;
+ if ( copy_from_guest_offset(&msr, vmsrs->msrs, i, 1) )
+ break;
+
+ ret = -EINVAL;
+ if ( msr.reserved )
+ break;
+
+ switch ( msr.index )
+ {
+ case MSR_AMD64_DR0_ADDRESS_MASK:
+ if ( !boot_cpu_has(X86_FEATURE_DBEXT) ||
+ (msr.value >> 32) )
+ break;
+ v->arch.pv_vcpu.dr_mask[0] = msr.value;
+ continue;
+
+ case MSR_AMD64_DR1_ADDRESS_MASK ...
+ MSR_AMD64_DR3_ADDRESS_MASK:
+ if ( !boot_cpu_has(X86_FEATURE_DBEXT) ||
+ (msr.value >> 32) )
+ break;
+ msr.index -= MSR_AMD64_DR1_ADDRESS_MASK - 1;
+ v->arch.pv_vcpu.dr_mask[msr.index] = msr.value;
+ continue;
+ }
+ break;
+ }
+
+ vcpu_unpause(v);
+
+ if ( i == vmsrs->msr_count )
+ ret = 0;
+ }
+ }
+ break;
+
default:
ret = iommu_do_domctl(domctl, d, u_domctl);
break;
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 385b053..7a13e25 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -895,6 +895,34 @@ struct xen_domctl_cacheflush {
typedef struct xen_domctl_cacheflush xen_domctl_cacheflush_t;
DEFINE_XEN_GUEST_HANDLE(xen_domctl_cacheflush_t);
+#if defined(__i386__) || defined(__x86_64__)
+struct xen_domctl_vcpu_msr {
+ uint32_t index;
+ uint32_t reserved;
+ uint64_aligned_t value;
+};
+typedef struct xen_domctl_vcpu_msr xen_domctl_vcpu_msr_t;
+DEFINE_XEN_GUEST_HANDLE(xen_domctl_vcpu_msr_t);
+
+/*
+ * XEN_DOMCTL_set_vcpu_msrs / XEN_DOMCTL_get_vcpu_msrs.
+ *
+ * For GET, a NULL 'msrs' guest handle is a request for the maximum
+ * 'msr_count' which is required to save the vcpu state.
+ *
+ * When actually getting the MSRs, 'msr_count' shall reflect the actual number
+ * of MSRs saved, which might be fewer than the maximum, if some are not
+ * currently used by the vcpu.
+ */
+struct xen_domctl_vcpu_msrs {
+ uint32_t vcpu; /* IN */
+ uint32_t msr_count; /* IN/OUT */
+ XEN_GUEST_HANDLE_64(xen_domctl_vcpu_msr_t) msrs; /* IN/OUT */
+};
+typedef struct xen_domctl_vcpu_msrs xen_domctl_vcpu_msrs_t;
+DEFINE_XEN_GUEST_HANDLE(xen_domctl_vcpu_msrs_t);
+#endif
+
struct xen_domctl {
uint32_t cmd;
#define XEN_DOMCTL_createdomain 1
@@ -965,6 +993,8 @@ struct xen_domctl {
#define XEN_DOMCTL_getnodeaffinity 69
#define XEN_DOMCTL_set_max_evtchn 70
#define XEN_DOMCTL_cacheflush 71
+#define XEN_DOMCTL_get_vcpu_msrs 72
+#define XEN_DOMCTL_set_vcpu_msrs 73
#define XEN_DOMCTL_gdbsx_guestmemio 1000
#define XEN_DOMCTL_gdbsx_pausevcpu 1001
#define XEN_DOMCTL_gdbsx_unpausevcpu 1002
@@ -1014,6 +1044,7 @@ struct xen_domctl {
#if defined(__i386__) || defined(__x86_64__)
struct xen_domctl_cpuid cpuid;
struct xen_domctl_vcpuextstate vcpuextstate;
+ struct xen_domctl_vcpu_msrs vcpu_msrs;
#endif
struct xen_domctl_set_access_required access_required;
struct xen_domctl_audit_p2m audit_p2m;
--
1.7.10.4
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