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KVM: x86/mmu: Add module param to disable MMIO caching (for testing)

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Add a module param to disable MMIO caching so that it's possible to test
the related flows without access to the necessary hardware.  Using shadow
paging with 64-bit KVM and 52 bits of physical address space must disable
MMIO caching as there are no reserved bits to be had.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-12-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2021-02-25 12:47:36 -08:00 committed by Paolo Bonzini
parent 8120337a4c
commit b09763da4d
1 changed files with 6 additions and 0 deletions
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6
arch/x86/kvm/mmu/spte.c
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@ -17,6 +17,9 @@
#include <asm/e820/api.h>
static bool __read_mostly enable_mmio_caching = true;
module_param_named(mmio_caching, enable_mmio_caching, bool, 0444);
u64 __read_mostly shadow_nx_mask;
u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
u64 __read_mostly shadow_user_mask;
@ -251,6 +254,9 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask)
BUG_ON((u64)(unsigned)access_mask != access_mask);
WARN_ON(mmio_value & shadow_nonpresent_or_rsvd_lower_gfn_mask);
if (!enable_mmio_caching)
mmio_value = 0;
/*
* Disable MMIO caching if the MMIO value collides with the bits that
* are used to hold the relocated GFN when the L1TF mitigation is