lkml.org 
[lkml]   [2022]   [Apr]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [RFC PATCH v5 042/104] KVM: x86/mmu: Track shadow MMIO value/mask on a per-VM basis
From
On 3/4/22 20:48, isaku.yamahata@intel.com wrote:
> + if (enable_ept) {
> + const u64 init_value = enable_tdx ? VMX_EPT_SUPPRESS_VE_BIT : 0ull;
> kvm_mmu_set_ept_masks(enable_ept_ad_bits,
> - cpu_has_vmx_ept_execute_only());
> + cpu_has_vmx_ept_execute_only(), init_value);
> + kvm_mmu_set_spte_init_value(init_value);
> + }

I think kvm-intel.ko should use VMX_EPT_SUPPRESS_VE_BIT unconditionally
as the init value. The bit is ignored anyway if the "EPT-violation #VE"
execution control is 0. Otherwise looks good, but I have a couple more
crazy ideas:

1) there could even be a test mode where KVM enables the execution
control, traps #VE in the exception bitmap, and shouts loudly if it gets
a #VE. That might avoid hard-to-find bugs due to forgetting about
VMX_EPT_SUPPRESS_VE_BIT.

2) or even, perhaps the init_value for the TDP MMU could set bit 63
_unconditionally_, because KVM always sets the NX bit on AMD hardware.
That would remove the whole infrastructure to keep shadow_init_value,
because it would be constant 0 in mmu.c and constant BIT(63) in tdp_mmu.c.

Sean, what do you think?

Paolo

\
 
 \ /
  Last update: 2022-04-06 01:11    [W:1.213 / U:0.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site