Ingo Molnar wrote:
> Subject: [patch] KVM: always reload segment selectors
> From: Ingo Molnar <[EMAIL PROTECTED]>
>
> failed VM entry on VMX might still change %fs or %gs, thus make sure
> that KVM always reloads the segment selectors. This is crutial on both
> x86 and x86_64: x86 has __KERNEL_PDA in %fs on which things like
> 'current' depends and x86_64 has 0 there and needs MSR_GS_BASE to work.
>
> Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
> ---
> drivers/kvm/vmx.c | 37 +++++++++++++++++++++----------------
> 1 file changed, 21 insertions(+), 16 deletions(-)
>
> Index: linux/drivers/kvm/vmx.c
> ===================================================================
> --- linux.orig/drivers/kvm/vmx.c
> +++ linux/drivers/kvm/vmx.c
> @@ -1896,6 +1896,27 @@ again:
> [cr2]"i"(offsetof(struct kvm_vcpu, cr2))
> : "cc", "memory" );
>
> + /*
> + * Reload segment selectors ASAP. (it's needed for a functional
> + * kernel: x86 relies on having __KERNEL_PDA in %fs and x86_64
> + * relies on having 0 in %gs for the CPU PDA to work.)
> + */
> + if (fs_gs_ldt_reload_needed) {
> + load_ldt(ldt_sel);
> + load_fs(fs_sel);
> + /*
> + * If we have to reload gs, we must take care to
> + * preserve our gs base.
> + */
> + local_irq_disable();
> + load_gs(gs_sel);
> +#ifdef CONFIG_X86_64
> + wrmsrl(MSR_GS_BASE, vmcs_readl(HOST_GS_BASE));
> +#endif
> + local_irq_enable();
> +
> + reload_tss();
> + }
> ++kvm_stat.exits;
>
> save_msrs(vcpu->guest_msrs, NR_BAD_MSRS);
btw, looking at the code, we could just remove fs from the
fs_gs_reload_needed and make in unconditional. VT knows how to reload
segments, except if they're user segments (groan). In the case of fs,
if it's used for the pda, it's obviously a kernel segment.
gs is different: since only the segment base is loaded (via swapgs), the
selector part could well be a userspace selector, and thus the
irq-protected reload is needed.
Anyway, I'm applying the patch as the above discourse is irrelevant to
the fix.
--
error compiling committee.c: too many arguments to function
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