On 03/08/2016 06:02 PM, Paolo Bonzini wrote:
On 08/03/2016 10:32, Xiao Guangrong wrote:
On 03/08/2016 04:47 PM, Paolo Bonzini wrote:
Some XSAVE features (currently only MPX, but in the future PKRU too)
will force eagerfpu on, see fpu__init_system_ctx_switch:
if (xfeatures_mask & XFEATURE_MASK_EAGER) {
if (eagerfpu == DISABLE) {
xfeatures_mask &= ~XFEATURE_MASK_EAGER;
So if the kernel parameter, eagerfpu is set to "off", then eager is not
enabled, so PKRU can not work in KVM?
Yes. Neither PKRU nor MPX.
Er... I noticed fpregs is not switched if the CPU is running in KVM module
(vcpu is not scheduled out and does not exit to userspace), that is why
read_pkru() can be used to read guest's PKRU in the patch 4.
However, then guest can fully control the access of userspace's memory if
CR4.PKRU is enabled on host and KVM needs to access QEMU's memory to do some
emulation anyway. Is it really safe？
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