[PATCH 11/24] KVM: x86/mmu: Add module param to disable MMIO caching (for testing)
From: Sean Christopherson <seanjc@google.com>
Date: 2021-02-25 20:58:40
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Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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> --- arch/x86/kvm/mmu/spte.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
index b2379094a8c1..503dec3f8c7a 100644
--- a/arch/x86/kvm/mmu/spte.c
+++ b/arch/x86/kvm/mmu/spte.c@@ -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
--
2.30.1.766.gb4fecdf3b7-goog