Re: [PATCH] SMP: Setup multiple tss for real mode emulation

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

He, Qing wrote:
> This patch sets up multiple TSS for real mode emulation on Intel vmx,
> one for each vcpu. This is a preparation patch for full SMP real mode
> support.
>
>   

Why are separate tss's needed?  Can't all vcpus use the same tss?

> Signed-off-by: Qing He <qing.he-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
>
>
> kvm.h      |    1 +
> kvm_main.c |    1 +
> vmx.c      |   31 +++++++++++++++++--------------
> 3 files changed, 19 insertions(+), 14 deletions(-)
>
>
> diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
> index 65ab268..0f7a4d9 100644
> --- a/drivers/kvm/kvm.h
> +++ b/drivers/kvm/kvm.h
> @@ -328,6 +328,7 @@ void kvm_io_bus_register_dev(struct kvm_io_bus *bus,
>  
>  struct kvm_vcpu {
>  	struct kvm *kvm;
> +	int vcpu_id;
>   

Switching to ->vcpu_id instead of computing (vcpu - vcpu->kvm->vcpus) is
a good idea (and necessary when separately allocating vcpus).  But in
its own patch, please.

> -	vmcs_write16(GUEST_CS_SELECTOR, 0xf000);
> -	vmcs_writel(GUEST_CS_BASE, 0x000f0000);
> -	vmcs_write32(GUEST_CS_LIMIT, 0xffff);
> -	vmcs_write32(GUEST_CS_AR_BYTES, 0x9b);
> +	if (vcpu->vcpu_id == 0) {
> +		vmcs_write16(GUEST_CS_SELECTOR, 0xf000);
> +		vmcs_writel(GUEST_CS_BASE, 0x000f0000);
> +		vmcs_write32(GUEST_CS_LIMIT, 0xffff);
> +		vmcs_write32(GUEST_CS_AR_BYTES, 0x9b);
> +		vmcs_writel(GUEST_RIP, 0xfff0);
> +	}
>  
>  	

Since you're not initializing these registers for vcpu_id != 0, we might
as well not touch this code.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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