Mohammed Gamal wrote:
On Sun, Aug 10, 2008 at 11:09 AM, Avi Kivity <[EMAIL PROTECTED]> wrote:
Mohammed Gamal wrote:
This patch aims to allow emulation whenever guest state is not valid for
VMX operation. This usually happens in mode switches with guests such as
older versions of gfxboot and FreeDOS with HIMEM.
The patch aims to address this issue, it introduces the following:
- A function that invokes the x86 emulator when the guest state is not
valid (borrowed from Guillaume Thouvenin's real mode patches)
- A function that checks that guest register state is VMX compliant
- A module parameter that enables these operations. It is disabled by
default, in order not to intervene with KVM's normal operation
+/*
+ * Check if guest state is valid. Returns true if valid, false if
+ * not.
+ * We assume that registers are always usable
+ */
+static bool guest_state_valid(struct kvm_vcpu *vcpu)
+{
...
+ /* vm86 mode guest state checks */
+ if(vcpu->arch.rmode.active) {
Better to check cr0 here.
Why? when cr0.PE bit is cleared, enter_rmode() is called and
vcpu->arch.rmode.active is set, or do you mean it should be checked in
addition?
No, instead. If we check cr0 then the function only depends on guest
state and is therefore easier to understand.
Eventually rmode.active will go away.
+ /* Check segment limits */
+ if( (cs_limit != 0xffff) || (ds_limit != 0xffff) ||
+ (ss_limit != 0xffff) || (es_limit != 0xffff) ||
+ (fs_limit != 0xffff) || (gs_limit != 0xffff) )
+ return false;
Would be nice to get code reuse, here and below (i.e. data_segment_valid()
for ds,es..gs.). Also, vmx_get_segment() will make the code tidier.
I think the function can be further broken down into smaller functions
each checking for a certain segment parameter (e.g.
segment_limit_valid(), segment_ar_valid(), rip_valid() ...etc.) and
then call all these functions in guest_state_valid().
Sure.
--
error compiling committee.c: too many arguments to function
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