For platforms that do not support XSAVES/XRSTORS instructions, like QEMU,
executing these instructions causes #UD.
This patch adds the check before the execution of XSAVES/XRSTORS instructions.
It also refines the logic inside rstore_xsave_area for the following reason:
If XSAVES/XRSTORS instructions are supported, restore XSAVE area if any of the
following conditions is met:
1. "vcpu->launched" is false (state initialization for guest)
2. "vcpu->arch.xsave_enabled" is true (state restoring for guest)
* Before vCPU is launched, condition 1 is satisfied.
* After vCPU is launched, condition 2 is satisfied because
is_valid_xsave_combination() guarantees that "vcpu->arch.xsave_enabled"
is consistent with pcpu_has_cap(X86_FEATURE_XSAVES).
Therefore, the check against "vcpu->launched" and "vcpu->arch.xsave_enabled"
can be eliminated here.
Tracked-On: #6481
Signed-off-by: Shiqing Gao <shiqing.gao@intel.com>
Acked-by: Eddie Dong <eddie.dong@Intel.com>
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