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hv: check the capability of XSAVES/XRSTORS instructions before execution 

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>
This commit is contained in:
Shiqing Gao 2021-08-24 14:46:59 +08:00 committed by wenlingz
parent dea2574819
commit 51a747d9c8
1 changed files with 14 additions and 3 deletions
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17
hypervisor/arch/x86/guest/vcpu.c
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@ -832,9 +832,9 @@ void zombie_vcpu(struct acrn_vcpu *vcpu, enum vcpu_state new_state)
}
}
void save_xsave_area(struct acrn_vcpu *vcpu, struct ext_context *ectx)
void save_xsave_area(__unused struct acrn_vcpu *vcpu, struct ext_context *ectx)
{
if (vcpu->arch.xsave_enabled) {
if (pcpu_has_cap(X86_FEATURE_XSAVES)) {
ectx->xcr0 = read_xcr(0);
write_xcr(0, ectx->xcr0 | XSAVE_SSE);
xsaves(&ectx->xs_area, UINT64_MAX);
@ -843,7 +843,18 @@ void save_xsave_area(struct acrn_vcpu *vcpu, struct ext_context *ectx)
void rstore_xsave_area(const struct acrn_vcpu *vcpu, const struct ext_context *ectx)
{
if ((!vcpu->launched) || (vcpu->arch.xsave_enabled)) {
if (pcpu_has_cap(X86_FEATURE_XSAVES)) {
/*
* 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.
*/
write_xcr(0, ectx->xcr0 | XSAVE_SSE);
msr_write(MSR_IA32_XSS, vcpu_get_guest_msr(vcpu, MSR_IA32_XSS));
xrstors(&ectx->xs_area, UINT64_MAX);