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Re: [Xen-devel] [PATCH 3/8] x86/vm-event/monitor: relocate code-motion more appropriately
On 7/4/2016 5:58 PM, Jan Beulich wrote:
On 04.07.16 at 13:02, <czuzu@xxxxxxxxxxxxxxx> wrote:
On 7/4/2016 1:22 PM, Jan Beulich wrote:
On 30.06.16 at 20:43, <czuzu@xxxxxxxxxxxxxxx> wrote:
@@ -119,6 +156,55 @@ bool_t monitored_msr(const struct domain *d, u32 msr)
return test_bit(msr, bitmap);
}
+static void write_ctrlreg_adjust_traps(struct domain *d)
+{
+ struct vcpu *v;
+ struct arch_vmx_struct *avmx;
+ unsigned int cr3_bitmask;
+ bool_t cr3_vmevent, cr3_ldexit;
+
+ /* Adjust CR3 load-exiting. */
+
+ /* vmx only */
+ ASSERT(cpu_has_vmx);
+
+ /* non-hap domains trap CR3 writes unconditionally */
+ if ( !paging_mode_hap(d) )
+ {
+ for_each_vcpu ( d, v )
+ ASSERT(v->arch.hvm_vmx.exec_control & CPU_BASED_CR3_LOAD_EXITING);
+ return;
+ }
+
+ cr3_bitmask = monitor_ctrlreg_bitmask(VM_EVENT_X86_CR3);
+ cr3_vmevent = !!(d->arch.monitor.write_ctrlreg_enabled & cr3_bitmask);
+
+ for_each_vcpu ( d, v )
+ {
+ avmx = &v->arch.hvm_vmx;
+ cr3_ldexit = !!(avmx->exec_control & CPU_BASED_CR3_LOAD_EXITING);
+
+ if ( cr3_vmevent == cr3_ldexit )
+ continue;
+
+ /*
+ * If CR0.PE=0, CR3 load exiting must remain enabled.
+ * See vmx_update_guest_cr code motion for cr = 0.
+ */
+ if ( cr3_ldexit && !hvm_paging_enabled(v) && !vmx_unrestricted_guest(v)
)
+ continue;
+
+ if ( cr3_vmevent )
+ avmx->exec_control |= CPU_BASED_CR3_LOAD_EXITING;
+ else
+ avmx->exec_control &= ~CPU_BASED_CR3_LOAD_EXITING;
+
+ vmx_vmcs_enter(v);
+ vmx_update_cpu_exec_control(v);
+ vmx_vmcs_exit(v);
+ }
+}
While Razvan gave his ack already, I wonder whether it's really a
good idea to put deeply VMX-specific code outside of a VMX-specific
file.
Well, a summary of what this function does would sound like: "adjusts
CR3 load-exiting for cr-write monitor vm-events". IMHO that's (monitor)
vm-event specific enough to be placed within the vm-event subsystem.
Could you suggest concretely how this separation would look like? (where
to put this function/parts of it (and what parts), what name should it
have once moved).
I won't go into that level of detail. Fact is that VMX-specific code
should be kept out of here. Whether you move the entire function
behind a hvm_funcs hook or just part of it is of no interest to me.
In no case should, if and when SVM eventually gets supported for
vm-event/monitor too, this function end up doing both VMX and SVM
specific things.
Jan
Why move it behind a hvm_funcs hook if it's only valid for VMX? SVM
support is not currently implemented, hence the ASSERT(cpu_has_vmx) at
the beginning of the function.
And of course if @ some point SVM support will be implemented then the
right thing to do is what you say, i.e. make this function part of
hvm_function_table, but until then I don't see why we should do that.
Note that arch_monitor_get_capabilities also returns no capability at
the moment if !cpu_has_vmx.
What if I move the vmx-specific parts to vmx.c in a function called
something like vmx_vm_event_update_cr3_traps() and call it from
write_ctrlreg_adjust_traps instead?...
Corneliu.
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